refactor: separate traffic and bikeshare components

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Traffic and bikeshare components
+
+- Separate traffic loading, animation, styling and lifecycle into factory-owned components.
+- Give each flow source its own bounded decode cache and cancellation checks.
+- Separate bikeshare registry, station requests, rendering, selection and proximity handling.
+
 ## Installation and context components
 
 - Separate mapped-site requests, records, placement, selection and viewport lifecycle.

docs/CURRENT-STATE.md

@@ -1,5 +1,13 @@
 # God's Eye View Current State
 
+Traffic and bikeshare expose factories through `./layers/traffic` and
+`./layers/bikeshare`. Traffic separates road requests, ingestion, animation,
+flow matching, styling, viewport lifecycle and development timing. Each source
+owns its decoded flow cache; cancelled bodies cannot refill it. Bikeshare
+separates its city registry, station source, parsing, rendering, selection and
+proximity lifecycle. Existing standalone sources, live/simulated labels, road
+budgets, station availability and polling behavior are retained.
+
 Installations and proximity context now expose `./layers/installations` and
 `./layers/awareness` factories. Each owns its records, selection, presentation,
 navigation and lifecycle. The standalone entries supply existing scene operations

package.json

@@ -152,6 +152,8 @@
     "./layers/satellites": "./src/layers/satellites/index.js",
     "./layers/launches": "./src/layers/launches/index.js",
     "./layers/installations": "./src/layers/installations/index.js",
-    "./layers/awareness": "./src/layers/awareness/index.js"
+    "./layers/awareness": "./src/layers/awareness/index.js",
+    "./layers/traffic": "./src/layers/traffic/index.js",
+    "./layers/bikeshare": "./src/layers/bikeshare/index.js"
   }
 }

scripts/format-scope.json

@@ -390,5 +390,41 @@
   "src/layers/awareness/subject.js",
   "src/data/militaryInstallations.js",
   "src/data/militaryAwareness.js",
-  "src/layers/installations/source.test.mjs"
+  "src/layers/installations/source.test.mjs",
+  "src/layers/traffic/flow.js",
+  "src/layers/traffic/lifecycle.js",
+  "src/layers/traffic/viewport.js",
+  "src/layers/traffic/controls.js",
+  "src/layers/traffic/source.js",
+  "src/layers/traffic/state.js",
+  "src/layers/traffic/policy.js",
+  "src/layers/traffic/rendering.js",
+  "src/layers/traffic/ingestion.js",
+  "src/layers/traffic/flowSource.js",
+  "src/layers/traffic/animation.js",
+  "src/layers/traffic/index.js",
+  "src/layers/traffic/flowDecode.js",
+  "src/layers/traffic/model.js",
+  "src/layers/traffic/timing.js",
+  "src/layers/traffic/style.js",
+  "src/layers/bikeshare/lifecycle.js",
+  "src/layers/bikeshare/viewport.js",
+  "src/layers/bikeshare/registry.js",
+  "src/layers/bikeshare/controls.js",
+  "src/layers/bikeshare/source.js",
+  "src/layers/bikeshare/state.js",
+  "src/layers/bikeshare/policy.js",
+  "src/layers/bikeshare/rendering.js",
+  "src/layers/bikeshare/testing.js",
+  "src/layers/bikeshare/ingestion.js",
+  "src/layers/bikeshare/queries.js",
+  "src/layers/bikeshare/index.js",
+  "src/layers/bikeshare/model.js",
+  "src/layers/bikeshare/selection.js",
+  "src/data/traffic.js",
+  "src/data/bikeshare.js",
+  "src/data/flowTiles.js",
+  "src/layers/traffic/source.test.mjs",
+  "src/layers/bikeshare/source.test.mjs",
+  "scripts/traffic-fixtures.mjs"
 ]

scripts/package-boundaries.json

@@ -808,5 +808,53 @@
       "src/ui/panelRailGeometry.js"
     ],
     "external": ["cesium"]
+  },
+  "traffic-layer": {
+    "exports": ["./layers/traffic"],
+    "modules": [
+      "src/data/flowMatch.js",
+      "src/data/tomtomTiles.js",
+      "src/data/trafficBounds.js",
+      "src/data/trafficFlowStyle.js",
+      "src/data/trafficPresetStyle.js",
+      "src/data/trafficQueue.js",
+      "src/layers/traffic/animation.js",
+      "src/layers/traffic/controls.js",
+      "src/layers/traffic/flow.js",
+      "src/layers/traffic/flowDecode.js",
+      "src/layers/traffic/flowSource.js",
+      "src/layers/traffic/index.js",
+      "src/layers/traffic/ingestion.js",
+      "src/layers/traffic/lifecycle.js",
+      "src/layers/traffic/model.js",
+      "src/layers/traffic/policy.js",
+      "src/layers/traffic/rendering.js",
+      "src/layers/traffic/source.js",
+      "src/layers/traffic/state.js",
+      "src/layers/traffic/style.js",
+      "src/layers/traffic/timing.js",
+      "src/layers/traffic/viewport.js"
+    ],
+    "external": ["cesium", "pbf", "@mapbox/vector-tile"]
+  },
+  "bikeshare-layer": {
+    "exports": ["./layers/bikeshare"],
+    "modules": [
+      "src/layers/bikeshare/controls.js",
+      "src/layers/bikeshare/index.js",
+      "src/layers/bikeshare/ingestion.js",
+      "src/layers/bikeshare/lifecycle.js",
+      "src/layers/bikeshare/model.js",
+      "src/layers/bikeshare/policy.js",
+      "src/layers/bikeshare/queries.js",
+      "src/layers/bikeshare/registry.js",
+      "src/layers/bikeshare/rendering.js",
+      "src/layers/bikeshare/selection.js",
+      "src/layers/bikeshare/source.js",
+      "src/layers/bikeshare/state.js",
+      "src/layers/bikeshare/testing.js",
+      "src/layers/bikeshare/viewport.js"
+    ],
+    "external": ["cesium"]
   }
 }

scripts/qa-traffic.mjs

@@ -25,6 +25,8 @@
  * Visual proof saved to qa-shots/ (gitignored).
  *
  * Run:  node scripts/qa-traffic.mjs --url http://localhost:4410
+ * Add --fixtures for synthetic roads and the recorded flow tile without a key;
+ * that mode does not qualify live source access or quota accounting.
  * Exits non-zero on any FAIL. Does not commit anything.
  */
 
@@ -44,6 +46,8 @@ const getOpt = (name, dflt) => {
 };
 const APP_URL = getOpt('--url', 'http://localhost:4410');
 const HEADFUL = argv.includes('--headful');
+const FIXTURES = argv.includes('--fixtures');
+const fixtureResponse = FIXTURES ? (await import('./traffic-fixtures.mjs')).trafficFixtureResponse : () => null;
 
 const CHROME_EXECUTABLE_CANDIDATES = [
   process.env.PUPPETEER_EXECUTABLE_PATH,
@@ -112,7 +116,8 @@ async function main() {
     process.exit(2);
   }
 
-  const statusBefore = await fetch(`${APP_URL}/api/tomtom/status`).then((r) => r.json()).catch(() => null);
+  const statusBefore = FIXTURES ? {hasKey:true,dailyCount:0} : await fetch(`${APP_URL}/api/tomtom/status`).then((r) => r.json()).catch(() => null);
+  if (FIXTURES) console.log('Source mode: synthetic roads and recorded flow tiles; live quota is not qualified.');
   if (!statusBefore?.hasKey) {
     console.error('\x1b[31mServer has no TomTom key — run against the keyed dev server (:4410).\x1b[0m');
     process.exit(2);
@@ -133,6 +138,11 @@ async function main() {
   let exitCode = 0;
   try {
     const page = await browser.newPage();
+    const onFixture = (request) => {
+      const response = fixtureResponse(request);
+      if (response) void request.respond(response); else void request.continue();
+    };
+    if (FIXTURES) { await page.setRequestInterception(true); page.on('request', onFixture); }
     await page.setViewport({ width: 1440, height: 900 });
 
     // Track flow-tile requests + traffic console lines for (ii)/(iii)/(v).
@@ -152,7 +162,8 @@ async function main() {
       () => window.__godsEyeView?.viewer && window.__godsEyeView?.dataManager,
       { timeout: 60000 },
     );
-    await sleep(1500);
+    await sleep(5000);
+    await page.keyboard.press('Escape');
 
     // ── (i) LIVE mode: San Antonio — fast Overpass extract, partial TomTom
     // coverage (sim dots exist for (iv)). Mumbai proved too Overpass-cold for
@@ -240,16 +251,17 @@ async function main() {
     // ── (iii) budget honesty ─────────────────────────────────────────────────
     console.log('\n(iii) Budget — dailyCount grew by ≤ requests this run...');
     {
-      const statusAfter = await fetch(`${APP_URL}/api/tomtom/status`).then((r) => r.json());
+      const statusAfter = FIXTURES ? statusBefore : await fetch(`${APP_URL}/api/tomtom/status`).then((r) => r.json());
       const grew = statusAfter.dailyCount - statusBefore.dailyCount;
       const ok = grew >= 0 && grew <= flowRequests.length;
-      record('BUDGET: /api/tomtom/status growth ≤ page tile requests', ok,
-        `before=${statusBefore.dailyCount} after=${statusAfter.dailyCount} pageRequests=${flowRequests.length}`);
+      record('BUDGET: /api/tomtom/status growth ≤ page tile requests', FIXTURES ? null : ok,
+        FIXTURES ? 'Synthetic source mode; live quota was not exercised' : `before=${statusBefore.dailyCount} after=${statusAfter.dailyCount} pageRequests=${flowRequests.length}`);
       if (!ok) exitCode = 1;
     }
 
     // ── (v) KEYLESS fallback (intercepted — server key untouched) ────────────
     console.log('\n(v) KEYLESS — intercepted status, expect pure simulation...');
+    if (FIXTURES) page.off('request', onFixture);
     await page.setRequestInterception(true);
     const keylessFlowReqs = [];
     page.on('request', (req) => {
@@ -263,6 +275,8 @@ async function main() {
         req.respond({ status: 503, contentType: 'application/json', body: JSON.stringify({ error: 'no_key' }) });
         return;
       }
+      const response = fixtureResponse(req);
+      if (response) { void req.respond(response); return; }
       try { req.continue(); } catch { /* already handled */ }
     });
     await page.reload({ waitUntil: 'domcontentloaded', timeout: 60000 });
@@ -270,7 +284,8 @@ async function main() {
       () => window.__godsEyeView?.viewer && window.__godsEyeView?.dataManager,
       { timeout: 60000 },
     );
-    await sleep(1500);
+    await sleep(5000);
+    await page.keyboard.press('Escape');
     let simStats = await settleTraffic(page, { lon: -98.4936, lat: 29.4241, height: 3000 }, { minCount: 100, timeoutS: 45 });
     if (!simStats || simStats.count === 0) {
       // Public Overpass can throttle bursts across harness runs — one retry.

scripts/traffic-fixtures.mjs

@@ -0,0 +1,56 @@
+import { readFileSync } from 'node:fs';
+import { decodeFlowTile } from '../src/layers/traffic/flowDecode.js';
+import { tilesForBounds } from '../src/data/tomtomTiles.js';
+
+const tile = readFileSync(
+  new URL(
+    '../src/data/fixtures/tomtom-flow-austin-12-935-1686.pbf',
+    import.meta.url,
+  ),
+);
+const json = (body) => ({
+  status: 200,
+  contentType: 'application/json',
+  body: JSON.stringify(body),
+});
+
+/** Reuse the recorded flow tile for an explicitly synthetic browser exercise. */
+export function trafficFixtureResponse(request) {
+  const url = new URL(request.url());
+  if (url.pathname === '/api/tomtom/status')
+    return json({ hasKey: true, dailyCount: 0 });
+  if (/^\/api\/tomtom\/flow\/\d+\/\d+\/\d+\.pbf$/.test(url.pathname))
+    return { status: 200, contentType: 'application/x-protobuf', body: tile };
+  if (url.pathname !== '/api/overpass') return null;
+  const query = new URLSearchParams(request.postData()).get('data') || '';
+  if (!query.includes('highway')) return null;
+  const match = query.match(/\((-?[\d.]+),(-?[\d.]+),(-?[\d.]+),(-?[\d.]+)\)/);
+  if (!match) throw new Error('Missing road fixture viewport');
+  const [south, west, north, east] = match.slice(1).map(Number);
+  const inside = ([lon, lat]) =>
+    lat >= south && lat <= north && lon >= west && lon <= east;
+  const segments = tilesForBounds({ south, west, north, east }, 12).flatMap(
+    ({ z, x, y }) => decodeFlowTile(tile, z, x, y),
+  );
+  const elements = segments
+    .filter((segment) => segment.coords.some(inside))
+    .slice(0, 240)
+    .map((segment, index) => ({
+      type: 'way',
+      id: index + 1,
+      tags: { highway: 'primary', oneway: 'yes' },
+      geometry: segment.coords.map(([lon, lat]) => ({ lon, lat })),
+    }));
+  const latitude = (south + north) / 2,
+    longitude = (west + east) / 2;
+  elements.push({
+    type: 'way',
+    id: 99999,
+    tags: { highway: 'residential' },
+    geometry: [
+      { lat: latitude, lon: longitude },
+      { lat: latitude + 0.003, lon: longitude + 0.003 },
+    ],
+  });
+  return json({ elements });
+}

src/data/fixtures/README.md

@@ -4,6 +4,6 @@
   tile (Mapbox Vector Tile protobuf, layer `"Traffic flow"`), downtown Austin
   z12 x935 y1686, captured 2026-07-16 from
   `api.tomtom.com/traffic/map/4/tile/flow/relative/12/935/1686.pbf`
-  (22,980 bytes). Used ONLY by `src/data/flowTiles.test.mjs` to pin MVT
-  decoding offline — it is a point-in-time congestion snapshot, not a bundled
-  data layer, and is never served to the app. © TomTom.
+  (22,980 bytes). Used by offline decode/source tests and the explicit `qa-traffic --fixtures`
+  browser mode — it is a point-in-time congestion snapshot, not a bundled
+  data layer, and is never loaded by ordinary application startup. © TomTom.

src/data/flowTiles.js

@@ -1,161 +1,6 @@
-import { PbfReader } from 'pbf';
-import { VectorTile } from '@mapbox/vector-tile';
-import { tilesForBounds } from './tomtomTiles.js';
-
-/**
- * @file TomTom traffic-flow vector-tile client: fetch + MVT decode.
- *
- * Fetches flow tiles from the local `/api/tomtom/flow/{z}/{x}/{y}.pbf` proxy
- * (the TomTom key never reaches the browser) and decodes the Mapbox Vector
- * Tile layer "Traffic flow" into plain lon/lat polylines with congestion
- * attributes. Consumed by the traffic layer's live mode
- * (`src/data/traffic.js` → `src/data/flowMatch.js`).
- *
- * Segment shape: `{coords: [[lon,lat],…], trafficLevel: 0..1, roadType: string,
- * closure: boolean}` — `trafficLevel` is TomTom's current/free-flow speed
- * ratio (1 = free flow). Features with a missing/non-finite `traffic_level`
- * are skipped unless `road_closure` is true (closures decode with level 0).
- *
- * Deps: `pbf@5` (PbfReader) + `@mapbox/vector-tile@3` — both tiny and
- * tree-shakeable; decoding happens client-side so the proxy stays a dumb
- * binary cache.
- *
- * @module data/flowTiles
- */
-
-export { tilesForBounds };
-
-/** @const {string} MVT layer name in TomTom flow tiles (verified live 2026-07-16). */
-const FLOW_LAYER_NAME = 'Traffic flow';
-/** @const {number} Ms — per-tile decode cache TTL (matches the proxy's 120 s tile TTL). */
-const DECODE_CACHE_TTL_MS = 120_000;
-/** @const {number} Max decoded tiles kept in memory before oldest-entry eviction. */
-const DECODE_CACHE_MAX_ENTRIES = 64;
-
-/**
- * Decoded-tile cache keyed by "z/x/y".
- * @type {Map<string, {at:number, segments:Array}>}
- */
-const _decodeCache = new Map();
-/** @type {number} Session count of tile requests issued to the proxy (decode-cache misses). */
-let _tilesFetched = 0;
-
-/**
- * Decode one TomTom flow tile (MVT protobuf) into flow segments.
- *
- * @param {Uint8Array|Buffer|ArrayBuffer} data - Raw .pbf tile bytes.
- * @param {number} z - Tile zoom (for tile-local → lon/lat projection).
- * @param {number} x - Tile column.
- * @param {number} y - Tile row.
- * @returns {Array<{coords:number[][], trafficLevel:number, roadType:string, closure:boolean}>}
- *   Flow polylines in [lon, lat] degrees. Returns [] for undecodable buffers
- *   or tiles without a "Traffic flow" layer (defensive — a corrupt tile must
- *   not kill the traffic layer).
- */
-export function decodeFlowTile(data, z, x, y) {
-  let layer;
-  try {
-    const bytes = data instanceof ArrayBuffer ? new Uint8Array(data) : data;
-    const tile = new VectorTile(new PbfReader(bytes));
-    layer = tile.layers[FLOW_LAYER_NAME];
-  } catch {
-    return [];
-  }
-  if (!layer) return [];
-
-  const segments = [];
-  for (let i = 0; i < layer.length; i++) {
-    let feature;
-    let geometry;
-    try {
-      feature = layer.feature(i);
-      geometry = feature.toGeoJSON(x, y, z).geometry;
-    } catch {
-      continue; // one malformed feature must not drop the tile
-    }
-    const props = feature.properties || {};
-    const closure = props.road_closure === true || props.road_closure === 'true';
-    const rawLevel = props.traffic_level;
-    const hasLevel = typeof rawLevel === 'number' && Number.isFinite(rawLevel);
-    // Skip features we can't color — unless closed (closures render dot-free
-    // regardless of level, so they stay useful without one).
-    if (!hasLevel && !closure) continue;
-    const trafficLevel = hasLevel ? Math.min(1, Math.max(0, rawLevel)) : 0;
-    const roadType = typeof props.road_type === 'string' ? props.road_type : '';
-
-    const lines = geometry.type === 'LineString'
-      ? [geometry.coordinates]
-      : geometry.type === 'MultiLineString'
-        ? geometry.coordinates
-        : [];
-    for (const coords of lines) {
-      if (!Array.isArray(coords) || coords.length < 2) continue;
-      segments.push({ coords, trafficLevel, roadType, closure });
-    }
-  }
-  return segments;
-}
-
-/** Insert into the decode cache with oldest-entry eviction. */
-function cacheSet(key, entry) {
-  if (!_decodeCache.has(key) && _decodeCache.size >= DECODE_CACHE_MAX_ENTRIES) {
-    const oldest = _decodeCache.keys().next().value;
-    _decodeCache.delete(oldest);
-  }
-  _decodeCache.set(key, entry);
-}
-
-/**
- * Fetch + decode all flow tiles covering the given bounds.
- *
- * Tiles are fetched from the local proxy in parallel; each decoded tile is
- * cached in memory for 120 s (keyed z/x/y), so repeat calls for the same
- * viewport are free. Partial tile failures return the segments that DID
- * decode (last-good philosophy); the promise rejects only when every tile
- * failed (e.g. keyless 503, aborted signal, proxy down).
- *
- * @param {{south:number, west:number, north:number, east:number}} bounds - Degrees.
- * @param {Object} [opts]
- * @param {AbortSignal} [opts.signal] - Abort signal (camera moved / layer disabled).
- * @param {number} [opts.zoom=12] - Flow tile zoom level.
- * @returns {Promise<Array<{coords:number[][], trafficLevel:number, roadType:string, closure:boolean}>>}
- *   Flat array of flow segments across all covering tiles.
- */
-export async function fetchFlowForBounds(bounds, { signal, zoom = 12 } = {}) {
-  const tiles = tilesForBounds(bounds, zoom);
-  if (tiles.length === 0) return [];
-  const now = Date.now();
-
-  const results = await Promise.allSettled(tiles.map(async ({ z, x, y }) => {
-    const key = `${z}/${x}/${y}`;
-    const cached = _decodeCache.get(key);
-    if (cached && now - cached.at < DECODE_CACHE_TTL_MS) return cached.segments;
-
-    _tilesFetched += 1;
-    const res = await fetch(`/api/tomtom/flow/${z}/${x}/${y}.pbf`, { signal });
-    if (!res.ok) throw new Error(`flow tile ${key}: HTTP ${res.status}`);
-    const segments = decodeFlowTile(await res.arrayBuffer(), z, x, y);
-    cacheSet(key, { at: Date.now(), segments });
-    return segments;
-  }));
-
-  const fulfilled = results.filter((r) => r.status === 'fulfilled');
-  if (fulfilled.length === 0) {
-    throw results[0].reason instanceof Error ? results[0].reason : new Error('flow fetch failed');
-  }
-  return fulfilled.flatMap((r) => r.value);
-}
-
-/**
- * Session diagnostics for `getStats()` surfaces.
- * @returns {{tilesFetched:number}} Count of tile requests issued to the proxy
- *   this session (decode-cache hits excluded).
- */
-export function getFlowSessionStats() {
-  return { tilesFetched: _tilesFetched };
-}
-
-/** Clear the decode cache (tests + layer teardown). Session stats persist. */
-export function resetFlowTileCache() {
-  _decodeCache.clear();
-}
+import { createFlowTileSource } from '../layers/traffic/flowSource.js';
+export { tilesForBounds } from './tomtomTiles.js';
+export { decodeFlowTile } from '../layers/traffic/flowDecode.js';
+const source = createFlowTileSource();
+export const { fetchFlowForBounds, getFlowSessionStats, resetFlowTileCache } =
+  source;

src/data/trafficTiming.test.mjs

@@ -1,11 +1,11 @@
 import assert from 'node:assert/strict';
-import { readFileSync } from 'node:fs';
+import { readLayerSource } from '../testSupport/readLayerSource.mjs';
 import test from 'node:test';
 import { fileURLToPath } from 'node:url';
 
 import { getTrafficTimingDiagnostics } from './traffic.js';
 
-const SOURCE = readFileSync(new URL('./traffic.js', import.meta.url), 'utf8');
+const SOURCE = readLayerSource(new URL('./traffic.js', import.meta.url), 'utf8').replace(/parts\.(?:model|timing)\./g, '');
 
 function functionBody(name) {
   const declaration = `function ${name}(`;
@@ -166,9 +166,8 @@ test('traffic timing pairs real ordering to the scheduling change and guards re-
       plugins: [{
         name: 'traffic-timing-test-hooks',
         transform(code, id) {
-          if (!id.endsWith('/src/data/traffic.js')) return null;
-          return `${code}\nexport const __trafficTimingTestHooks = {\n` +
-            `  currentAnchor: () => _trafficTimingCurrentAnchor,\n};\n`;
+          if (!id.endsWith('/src/layers/traffic/index.js')) return null;
+          return code.replace('return Object.assign(', 'return Object.assign({ __trafficTimingTestHooks: { currentAnchor: () => state._trafficTimingCurrentAnchor } },');
         },
       }],
     });
@@ -248,7 +247,7 @@ test('traffic timing pairs real ordering to the scheduling change and guards re-
     // and moveEnd arrives only after cameraEventWaitTime (~500 ms).
     setLongitude(-97.72);
     changed.raise();
-    const anchorA = traffic.__trafficTimingTestHooks.currentAnchor();
+    const anchorA = traffic.default.__trafficTimingTestHooks.currentAnchor();
     const anchorMarkA = performance.getEntriesByType('mark').find((entry) => (
       entry.detail?.segment === 'last-camera-change'
       && entry.detail?.interactionId === anchorA.interactionId
@@ -262,7 +261,7 @@ test('traffic timing pairs real ordering to the scheduling change and guards re-
       traceObjectsCreated: 1,
       uncorrelatedTracesDropped: 0,
     });
-    assert.equal(traffic.__trafficTimingTestHooks.currentAnchor(), null);
+    assert.equal(traffic.default.__trafficTimingTestHooks.currentAnchor(), null);
     const fetchFromA = performance.getEntriesByType('measure').find((entry) => (
       entry.detail?.segment === 'last-camera-change-to-fetch-start'
       && entry.detail?.interactionId === anchorA.interactionId
@@ -288,16 +287,16 @@ test('traffic timing pairs real ordering to the scheduling change and guards re-
     // and must count one drop without consuming C's current anchor.
     setLongitude(-97.70);
     changed.raise();
-    const anchorB = traffic.__trafficTimingTestHooks.currentAnchor();
+    const anchorB = traffic.default.__trafficTimingTestHooks.currentAnchor();
     const [timerBId, timerB] = pendingDebounce();
     setLongitude(-97.68);
     changed.raise();
-    const anchorC = traffic.__trafficTimingTestHooks.currentAnchor();
+    const anchorC = traffic.default.__trafficTimingTestHooks.currentAnchor();
     assert.notEqual(anchorC.interactionId, anchorB.interactionId);
     assert.equal(timeouts.has(timerBId), false, 'the ordinary debounce path must cancel B');
     await timerB.callback();
     assert.equal(
-      traffic.__trafficTimingTestHooks.currentAnchor().interactionId,
+      traffic.default.__trafficTimingTestHooks.currentAnchor().interactionId,
       anchorC.interactionId,
       'a stale callback must not consume the newer C anchor',
     );

src/layers/bikeshare/controls.js

@@ -0,0 +1,46 @@
+import { STATUS_POLL_MS } from './policy.js';
+
+export function createControls({ state: layerState, services, parts, source }) {
+  const methods = {
+    id: 'bikeshare',
+
+    name: 'Bikeshare',
+
+    icon: '🚲',
+
+    source: 'GBFS',
+
+    updateInterval: STATUS_POLL_MS,
+
+    /**
+     * Return a sampled array of detectable station objects for HUD overlay rendering.
+     * @param {Object} [options] - Sampling options (maxCount, seed).
+     * @returns {Array<{ position: Cesium.Cartesian3, id: string, type: string, skipLabel: boolean }>}
+     */
+    getDetectableObjects(options = {}) {
+      return parts.queries.collectDetectableStations(options);
+    },
+
+    /**
+     * Return current layer statistics for the UI status display.
+     * @returns {{ count: number, lastUpdate: number|null, loading: boolean, loadingLabel?: string, error?: string }}
+     */
+    getStats() {
+      const stats = {
+        count: layerState._count,
+        lastUpdate: layerState._lastUpdate,
+        loading: layerState._loading,
+      };
+      if (layerState._loading) {
+        stats.loadingLabel =
+          layerState._activeCityIds.size > 0
+            ? `syncing ${layerState._activeCityIds.size} city feeds...`
+            : 'scanning nearby systems...';
+      }
+      if (layerState._error) stats.error = layerState._error;
+      return stats;
+    },
+  };
+
+  return { methods };
+}

src/layers/bikeshare/index.js

@@ -0,0 +1,50 @@
+import { createIngestion } from './ingestion.js';
+import { createModel } from './model.js';
+import { createViewport } from './viewport.js';
+import { createRendering } from './rendering.js';
+import { createSelection } from './selection.js';
+import { createQueries } from './queries.js';
+import { createTesting } from './testing.js';
+import { createControls } from './controls.js';
+import { createLifecycle } from './lifecycle.js';
+import { createState } from './state.js';
+
+/** Construct one layer with its own scene state and supplied application services. */
+export function createBikeshareLayer({ services, source }) {
+  if (typeof source?.getStations !== 'function')
+    throw new TypeError('A bikeshare source is required');
+  const state = createState({ services });
+  const parts = {};
+  const context = { state, services, parts, source };
+  parts.ingestion = createIngestion(context);
+  parts.model = createModel(context);
+  parts.viewport = createViewport(context);
+  parts.rendering = createRendering(context);
+  parts.selection = createSelection(context);
+  parts.queries = createQueries(context);
+  parts.testing = createTesting(context);
+  parts.controls = createControls(context);
+  parts.lifecycle = createLifecycle(context);
+  return Object.assign(
+    {},
+    parts.controls.methods,
+    parts.lifecycle.methods,
+    parts.ingestion?.methods,
+    {
+      createBikeshareSelectedOverlayEntry:
+        parts.selection.createBikeshareSelectedOverlayEntry,
+      _setBikeshareSelectionStateForTest:
+        parts.testing._setBikeshareSelectionStateForTest,
+      _selectBikeshareStationForTest:
+        parts.testing._selectBikeshareStationForTest,
+      _clearBikeshareSelectionForTest:
+        parts.testing._clearBikeshareSelectionForTest,
+    },
+  );
+}
+export {
+  BIKESHARE_SELECTED_OVERLAY_SOURCE_ID,
+  BIKESHARE_SELECTED_OVERLAY_SOURCE_OPTIONS,
+} from './policy.js';
+
+export { createBikeshareSource } from './source.js';

src/layers/bikeshare/ingestion.js

@@ -0,0 +1,212 @@
+import { CITY_BY_ID } from './registry.js';
+
+export function createIngestion({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  /**
+   * Convert an upstream GBFS URL into a local proxy URL.
+   * The dev server proxies /api/gbfs/* to avoid CORS issues with third-party feeds.
+   * @param {string} upstreamUrl - Full HTTPS GBFS endpoint URL.
+   * @returns {string} Relative proxy URL.
+   */
+
+  function toProxyUrl(upstreamUrl) {
+    return `/api/gbfs/${encodeURIComponent(upstreamUrl)}`;
+  }
+
+  /** Increment the loading reference count and mark loading state active. */
+
+  function beginLoading() {
+    layerState._loadingOps++;
+    layerState._loading = true;
+  }
+
+  /** Decrement the loading reference count; clear loading flag when zero. */
+
+  function endLoading() {
+    layerState._loadingOps = Math.max(0, layerState._loadingOps - 1);
+    layerState._loading = layerState._loadingOps > 0;
+  }
+
+  /**
+   * Fetch and parse JSON from a GBFS endpoint via the local proxy.
+   * @param {string} upstreamUrl - Full HTTPS GBFS endpoint URL.
+   * @param {Object} [options]
+   * @param {AbortSignal} [options.signal] - Optional abort signal for cancellation.
+   * @returns {Promise<Object>} Parsed JSON payload.
+   * @throws {Error} On non-OK HTTP status or malformed JSON.
+   */
+
+  async function fetchGbfsJson(upstreamUrl, options) {
+    return source.getStations(upstreamUrl, options);
+  }
+
+  /**
+   * Abort an in-flight GBFS request for a specific city and remove it from the map.
+   * @param {Map<string, { controller: AbortController }>} map - In-flight request map.
+   * @param {string} cityId - City whose request should be cancelled.
+   */
+
+  function abortInFlight(map, cityId) {
+    const entry = map.get(cityId);
+    if (!entry) return;
+    try {
+      entry.controller?.abort();
+    } catch {
+      // no-op
+    }
+    map.delete(cityId);
+  }
+
+  /** Abort all in-flight station info and status requests across all cities. */
+
+  function abortAllInFlight() {
+    for (const cityId of layerState._inFlightInfo.keys())
+      abortInFlight(layerState._inFlightInfo, cityId);
+    for (const cityId of layerState._inFlightStatus.keys())
+      abortInFlight(layerState._inFlightStatus, cityId);
+  }
+
+  /**
+   * Load station information for a city. Returns cached data if available,
+   * deduplicates concurrent requests, and caches the result on success.
+   * Station info is static metadata (location, name, capacity) and is
+   * fetched once per city per session.
+   * @param {string} cityId - City identifier.
+   * @param {number} generation - Proximity generation to detect stale requests.
+   * @returns {Promise<Map<string, Object>>} Map of stationId to station info.
+   * @throws {Error} On unknown city, fetch failure, or empty station list.
+   */
+
+  async function loadCityStationInfo(cityId, generation) {
+    if (layerState._stationInfoCache.has(cityId))
+      return layerState._stationInfoCache.get(cityId);
+    const inFlight = layerState._inFlightInfo.get(cityId);
+    if (inFlight) return inFlight.promise;
+
+    const city = CITY_BY_ID.get(cityId);
+    if (!city) throw new Error(`Unknown GBFS city "${cityId}"`);
+    const controller = new AbortController();
+
+    const promise = (async () => {
+      beginLoading();
+      try {
+        const payload = await fetchGbfsJson(city.stationInformationUrl, {
+          signal: controller.signal,
+        });
+        const stationMap = parts.model.parseStationInformation(payload);
+        if (stationMap.size === 0) {
+          throw new Error(`No station information for ${city.city}`);
+        }
+        layerState._stationInfoCache.set(cityId, stationMap);
+        return stationMap;
+      } finally {
+        endLoading();
+      }
+    })().finally(() => {
+      // Clean up in-flight entry only if it is still ours (not replaced by a newer request)
+      const current = layerState._inFlightInfo.get(cityId);
+      if (current && current.controller === controller)
+        layerState._inFlightInfo.delete(cityId);
+    });
+
+    layerState._inFlightInfo.set(cityId, { promise, controller, generation });
+    return promise;
+  }
+
+  /**
+   * Load real-time station status for a city (bike/dock counts, operational flags).
+   * Unlike station info, status is NOT served from cache — it is always re-fetched
+   * to keep availability data current. Concurrent requests are deduplicated.
+   * @param {string} cityId - City identifier.
+   * @param {number} generation - Proximity generation to detect stale requests.
+   * @returns {Promise<Map<string, Object>>} Map of stationId to status objects.
+   * @throws {Error} On unknown city or fetch failure.
+   */
+
+  async function loadCityStationStatus(cityId, generation) {
+    const inFlight = layerState._inFlightStatus.get(cityId);
+    if (inFlight) return inFlight.promise;
+
+    const city = CITY_BY_ID.get(cityId);
+    if (!city) throw new Error(`Unknown GBFS city "${cityId}"`);
+    const controller = new AbortController();
+
+    const promise = (async () => {
+      beginLoading();
+      try {
+        const payload = await fetchGbfsJson(city.stationStatusUrl, {
+          signal: controller.signal,
+        });
+        const statusMap = parts.model.parseStationStatus(payload);
+        layerState._statusCache.set(cityId, {
+          statusMap,
+          timestamp: Date.now(),
+        });
+        return statusMap;
+      } finally {
+        endLoading();
+      }
+    })().finally(() => {
+      const current = layerState._inFlightStatus.get(cityId);
+      if (current && current.controller === controller)
+        layerState._inFlightStatus.delete(cityId);
+    });
+
+    layerState._inFlightStatus.set(cityId, { promise, controller, generation });
+    return promise;
+  }
+  const methods = {
+    /**
+     * Periodic update tick — re-fetches station status for all active cities
+     * and refreshes point colors/sizes. Called by the layer manager at
+     * STATUS_POLL_MS intervals.
+     * @returns {Promise<void>}
+     */
+    async update() {
+      if (!layerState._enabled || layerState._activeCityIds.size === 0) return;
+
+      const generation = layerState._proximityGeneration;
+      const cityIds = Array.from(layerState._activeCityIds);
+      await Promise.all(
+        cityIds.map(async (cityId) => {
+          try {
+            const statusMap = await loadCityStationStatus(cityId, generation);
+            if (
+              !layerState._enabled ||
+              !layerState._activeCityIds.has(cityId) ||
+              generation !== layerState._proximityGeneration
+            )
+              return;
+            parts.rendering.applyStatusToPoints(cityId, statusMap);
+          } catch (error) {
+            if (error?.name === 'AbortError') return;
+            console.warn(
+              `[Data:Bikeshare] ${cityId} status update error:`,
+              error,
+            );
+            layerState._error = 'GBFS status update failed';
+          }
+        }),
+      );
+
+      layerState._count = layerState._stationRenderMap.size;
+      if (layerState._count > 0) layerState._lastUpdate = Date.now();
+    },
+  };
+
+  return {
+    toProxyUrl,
+    beginLoading,
+    endLoading,
+    fetchGbfsJson,
+    abortInFlight,
+    abortAllInFlight,
+    loadCityStationInfo,
+    loadCityStationStatus,
+    methods,
+  };
+}

src/layers/bikeshare/lifecycle.js

@@ -0,0 +1,171 @@
+import * as Cesium from 'cesium';
+import { GBFS_CITY_REGISTRY } from './registry.js';
+import { BIKESHARE_SELECTED_OVERLAY_SOURCE_ID } from './policy.js';
+
+export function createLifecycle({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  const { registerSpriteCollection, restoreSpriteOrder } = services.sprites;
+  const { registerPickOwner, unregisterPickOwner } = services.picking;
+
+  const methods = {
+    /**
+     * Initialize the bikeshare layer. Creates the point primitive collection,
+     * resets all internal state, and installs the click handler.
+     * Called once during app bootstrap.
+     * @param {Cesium.Viewer} viewer - Cesium viewer instance.
+     */
+    init(viewer) {
+      layerState._viewer = viewer;
+      layerState._pointCollection = new Cesium.PointPrimitiveCollection({
+        blendOption: Cesium.BlendOption.TRANSLUCENT,
+      });
+      viewer.scene.primitives.add(layerState._pointCollection);
+      registerSpriteCollection('bikeshare', layerState._pointCollection);
+      layerState._pointCollection.show = false;
+
+      layerState._enabled = false;
+      layerState._cameraDebounceTimer = null;
+      layerState._cameraChangedAttached = false;
+      layerState._altitudeGateEnabled = false;
+      layerState._proximityGeneration = 0;
+
+      layerState._activeCityIds = new Set();
+      layerState._cityRuntime = new Map();
+      layerState._stationInfoCache = new Map();
+      layerState._statusCache = new Map();
+      layerState._inFlightInfo = new Map();
+      layerState._inFlightStatus = new Map();
+      layerState._stationRenderMap = new Map();
+      layerState._clickHandler = null;
+      layerState._selectedKey = null;
+      layerState._selectedEntity = null;
+      layerState._count = 0;
+      layerState._lastUpdate = null;
+      layerState._loading = false;
+      layerState._loadingOps = 0;
+      layerState._error = null;
+      layerState._limitWarned = false;
+
+      layerState._overlayHost.setVisible(
+        BIKESHARE_SELECTED_OVERLAY_SOURCE_ID,
+        false,
+      );
+
+      parts.selection._installClickHandler(viewer);
+
+      restoreSpriteOrder(viewer);
+
+      console.log(
+        `[Data:Bikeshare] Initialized with ${GBFS_CITY_REGISTRY.length} cities`,
+      );
+    },
+
+    /**
+     * Enable the bikeshare layer. Shows points, attaches the camera listener,
+     * and triggers an initial proximity check.
+     * @param {Cesium.Viewer} viewer - Cesium viewer instance.
+     */
+    enable(viewer) {
+      layerState._enabled = true;
+      layerState._error = null;
+      layerState._pointCollection.show = true;
+      layerState._overlayHost.setVisible(
+        BIKESHARE_SELECTED_OVERLAY_SOURCE_ID,
+        true,
+      );
+      parts.selection._installClickHandler(viewer);
+      // Pick-ownership (H2): station point ids are string render-map keys.
+      registerPickOwner('bikeshare', (pickedId) =>
+        layerState._stationRenderMap.has(pickedId),
+      );
+
+      if (!layerState._cameraChangedAttached) {
+        viewer.camera.changed.addEventListener(parts.viewport.onCameraChanged);
+        viewer.camera.percentageChanged = Math.min(
+          viewer.camera.percentageChanged || 1,
+          0.05,
+        );
+        layerState._cameraChangedAttached = true;
+      }
+
+      void parts.viewport.runProximityCheck();
+      restoreSpriteOrder(viewer);
+    },
+
+    /**
+     * Disable the bikeshare layer. Hides points, removes event listeners,
+     * aborts all pending fetches, and tears down all city data.
+     * @param {Cesium.Viewer} viewer - Cesium viewer instance.
+     */
+    disable(viewer) {
+      layerState._enabled = false;
+      layerState._proximityGeneration++;
+      layerState._altitudeGateEnabled = false;
+      clearTimeout(layerState._cameraDebounceTimer);
+      layerState._cameraDebounceTimer = null;
+      parts.selection._clearSelection();
+      layerState._overlayHost.setVisible(
+        BIKESHARE_SELECTED_OVERLAY_SOURCE_ID,
+        false,
+      );
+
+      if (layerState._clickHandler) {
+        layerState._clickHandler.destroy();
+        layerState._clickHandler = null;
+      }
+      document.removeEventListener('keydown', parts.selection._onKeyDown);
+      unregisterPickOwner('bikeshare');
+
+      if (layerState._cameraChangedAttached) {
+        viewer.camera.changed.removeEventListener(
+          parts.viewport.onCameraChanged,
+        );
+        layerState._cameraChangedAttached = false;
+      }
+
+      parts.ingestion.abortAllInFlight();
+      parts.viewport.deactivateAllCities();
+      layerState._cityRuntime.clear();
+      layerState._pointCollection.show = false;
+      layerState._count = 0;
+      layerState._loading = false;
+      layerState._loadingOps = 0;
+    },
+
+    /** Permanently release primitives, handlers, and the selected host source. */
+    destroy(viewer) {
+      if (layerState._enabled) this.disable(viewer);
+      else {
+        parts.selection._clearSelection();
+        layerState._overlayHost.setVisible(
+          BIKESHARE_SELECTED_OVERLAY_SOURCE_ID,
+          false,
+        );
+        if (layerState._clickHandler) {
+          layerState._clickHandler.destroy();
+          layerState._clickHandler = null;
+        }
+        document.removeEventListener('keydown', parts.selection._onKeyDown);
+        unregisterPickOwner('bikeshare');
+      }
+      if (layerState._cameraChangedAttached) {
+        viewer.camera.changed.removeEventListener(
+          parts.viewport.onCameraChanged,
+        );
+        layerState._cameraChangedAttached = false;
+      }
+      parts.ingestion.abortAllInFlight();
+      if (layerState._pointCollection) {
+        viewer.scene.primitives.remove(layerState._pointCollection);
+        layerState._pointCollection = null;
+      }
+      layerState._viewer = null;
+    },
+  };
+
+  return { methods };
+}

src/layers/bikeshare/model.js

@@ -0,0 +1,162 @@
+export function createModel({ state: layerState, services, parts, source }) {
+  /**
+   * Coerce a GBFS boolean field to a native boolean.
+   * GBFS feeds are inconsistent — some use booleans, others use 0/1 or strings.
+   * @param {*} value - Raw field value from GBFS JSON.
+   * @param {boolean} [fallback=true] - Default when value is null/undefined/unrecognized.
+   * @returns {boolean}
+   */
+
+  function normalizeGbfsBool(value, fallback = true) {
+    if (value == null) return fallback;
+    if (typeof value === 'boolean') return value;
+    const num = Number(value);
+    if (Number.isFinite(num)) return num !== 0;
+    const text = String(value).trim().toLowerCase();
+    if (text === 'true' || text === 'yes') return true;
+    if (text === 'false' || text === 'no') return false;
+    return fallback;
+  }
+
+  /**
+   * Parse a value as a non-negative integer, returning fallback on failure.
+   * @param {*} value - Raw numeric value.
+   * @param {number|null} [fallback=null] - Returned when value is not a valid non-negative number.
+   * @returns {number|null}
+   */
+
+  function toNonNegativeInteger(value, fallback = null) {
+    const n = Number(value);
+    if (!Number.isFinite(n) || n < 0) return fallback;
+    return Math.round(n);
+  }
+
+  /**
+   * Build a globally unique render key for a station.
+   * @param {string} cityId - City identifier.
+   * @param {string} stationId - Station identifier within the city.
+   * @returns {string} Composite key in "cityId:stationId" format.
+   */
+
+  function stationKey(cityId, stationId) {
+    return `${cityId}:${stationId}`;
+  }
+
+  /**
+   * Compute the great-circle distance between two points using the Haversine formula.
+   * @param {number} aLat - Latitude of point A in degrees.
+   * @param {number} aLon - Longitude of point A in degrees.
+   * @param {number} bLat - Latitude of point B in degrees.
+   * @param {number} bLon - Longitude of point B in degrees.
+   * @returns {number} Distance in kilometers.
+   */
+
+  function haversineKm(aLat, aLon, bLat, bLon) {
+    const toRad = (value) => (value * Math.PI) / 180;
+    const dLat = toRad(bLat - aLat);
+    const dLon = toRad(bLon - aLon);
+    const p1 = toRad(aLat);
+    const p2 = toRad(bLat);
+    const a =
+      Math.sin(dLat / 2) ** 2 +
+      Math.cos(p1) * Math.cos(p2) * Math.sin(dLon / 2) ** 2;
+    return 6371 * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+  }
+
+  /**
+   * Extract the stations array from a GBFS JSON payload.
+   * Handles multiple response shapes: { data: { stations: [...] } },
+   * { data: [...] }, and nested objects with a stations sub-key.
+   * @param {Object} payload - Parsed GBFS JSON response.
+   * @returns {Object[]} Array of raw station objects (may be empty).
+   */
+
+  function extractStationsArray(payload) {
+    const data = payload?.data;
+    if (Array.isArray(data?.stations)) return data.stations;
+    if (Array.isArray(data)) return data;
+    // Some feeds nest stations under an additional key (e.g. locale wrappers)
+    if (data && typeof data === 'object') {
+      for (const value of Object.values(data)) {
+        if (Array.isArray(value?.stations)) return value.stations;
+      }
+    }
+    return [];
+  }
+
+  /**
+   * Parse a GBFS station_information payload into a Map of station metadata.
+   * Handles field-name variations across different GBFS providers
+   * (station_id vs id, lat vs latitude, etc.). Stations with missing or
+   * invalid coordinates are silently skipped.
+   * @param {Object} payload - Parsed station_information.json response.
+   * @returns {Map<string, Object>} Map of stationId to station info objects.
+   */
+
+  function parseStationInformation(payload) {
+    const stations = extractStationsArray(payload);
+    const stationMap = new Map();
+
+    for (const raw of stations) {
+      // Accept both GBFS 2.x (station_id) and alternate (id) field names
+      const stationId = String(raw?.station_id ?? raw?.id ?? '').trim();
+      const lat = Number(raw?.lat ?? raw?.latitude);
+      const lon = Number(raw?.lon ?? raw?.longitude);
+      if (!stationId || !Number.isFinite(lat) || !Number.isFinite(lon))
+        continue;
+
+      stationMap.set(stationId, {
+        stationId,
+        name: String(raw?.name || raw?.short_name || '').trim(),
+        lat,
+        lon,
+        capacity: toNonNegativeInteger(raw?.capacity),
+        isInstalled: normalizeGbfsBool(raw?.is_installed, true),
+        isRenting: normalizeGbfsBool(raw?.is_renting, true),
+        isReturning: normalizeGbfsBool(raw?.is_returning, true),
+      });
+    }
+
+    return stationMap;
+  }
+
+  /**
+   * Parse a GBFS station_status payload into a Map of real-time availability.
+   * @param {Object} payload - Parsed station_status.json response.
+   * @returns {Map<string, Object>} Map of stationId to status objects containing
+   *   bikesAvailable, docksAvailable, and operational flags.
+   */
+
+  function parseStationStatus(payload) {
+    const stations = extractStationsArray(payload);
+    const statusMap = new Map();
+
+    for (const raw of stations) {
+      const stationId = String(raw?.station_id ?? raw?.id ?? '').trim();
+      if (!stationId) continue;
+
+      const bikes = toNonNegativeInteger(raw?.num_bikes_available);
+      const docks = toNonNegativeInteger(raw?.num_docks_available);
+      statusMap.set(stationId, {
+        stationId,
+        bikesAvailable: bikes,
+        docksAvailable: docks,
+        isInstalled: normalizeGbfsBool(raw?.is_installed, true),
+        isRenting: normalizeGbfsBool(raw?.is_renting, true),
+        isReturning: normalizeGbfsBool(raw?.is_returning, true),
+        lastReported: toNonNegativeInteger(raw?.last_reported),
+      });
+    }
+
+    return statusMap;
+  }
+  return {
+    normalizeGbfsBool,
+    toNonNegativeInteger,
+    stationKey,
+    haversineKm,
+    extractStationsArray,
+    parseStationInformation,
+    parseStationStatus,
+  };
+}

src/layers/bikeshare/policy.js

@@ -0,0 +1,85 @@
+import * as Cesium from 'cesium';
+
+export const BIKESHARE_SELECTED_OVERLAY_SOURCE_ID = 'bikeshare-selected';
+
+export const BIKESHARE_SELECTED_OVERLAY_SOURCE_OPTIONS = Object.freeze({
+  cohortLimit: 1,
+  collisionCapacity: 0,
+  moving: false,
+});
+
+// --- Activation / display thresholds ---
+/** Altitude (m) at which bikeshare layer becomes eligible for display. */
+
+export const ACTIVATION_ALTITUDE_M = 50000;
+
+/** Hysteresis enter threshold — layer activates when camera drops below this. */
+
+export const ACTIVATION_ENTER_ALTITUDE_M = ACTIVATION_ALTITUDE_M - 2000;
+
+/** Hysteresis exit threshold — layer deactivates when camera rises above this. */
+
+export const ACTIVATION_EXIT_ALTITUDE_M = ACTIVATION_ALTITUDE_M + 2000;
+
+/** Debounce interval (ms) for camera-change proximity checks. */
+
+export const CAMERA_DEBOUNCE_MS = 340;
+
+/** Default radius (km) for determining whether a city is in camera range. */
+
+export const CITY_RANGE_BASE_KM = 100;
+
+/** Polling interval (ms) for refreshing station status data. */
+
+export const STATUS_POLL_MS = 60000;
+
+// --- Point rendering constants ---
+/** Minimum rendered point size in pixels. */
+
+export const POINT_SIZE_MIN = 4;
+
+/** Maximum rendered point size in pixels. */
+
+export const POINT_SIZE_MAX = 12;
+
+/** Fallback station capacity when real data is unavailable. */
+
+export const DEFAULT_CAPACITY = 15;
+
+/** Vertical offset (m) above terrain for station points. */
+
+export const POINT_HEIGHT_OFFSET_M = 2.0;
+
+/** Hard cap on total rendered station points across all cities. */
+
+export const MAX_TOTAL_POINTS = 8000;
+
+// --- Availability color palette ---
+/** Station has >60% bikes available. */
+
+export const COLOR_GREEN =
+  Cesium.Color.fromCssColorString('#00ff88').withAlpha(0.95);
+
+/** Station has 30-60% bikes available. */
+
+export const COLOR_YELLOW =
+  Cesium.Color.fromCssColorString('#ffaa00').withAlpha(0.94);
+
+/** Station has <30% bikes available. */
+
+export const COLOR_RED =
+  Cesium.Color.fromCssColorString('#ff4444').withAlpha(0.94);
+
+/** No status data available for station. */
+
+export const COLOR_NEUTRAL =
+  Cesium.Color.fromCssColorString('#91a4b4').withAlpha(0.62);
+
+/** Station is offline (not installed, not renting, or not returning). */
+
+export const COLOR_MUTED =
+  Cesium.Color.fromCssColorString('#687581').withAlpha(0.48);
+
+/** Outline color for all station points. */
+
+export const COLOR_OUTLINE = Cesium.Color.BLACK.withAlpha(0.25);

src/layers/bikeshare/queries.js

@@ -0,0 +1,75 @@
+export function createQueries({ state: layerState, services, parts, source }) {
+  /**
+   * Build a compact HUD detection ID string for a station.
+   * Truncates long names to 24 chars for readability.
+   * @param {Object} record - Render record from _stationRenderMap.
+   * @returns {string} Formatted label like "Station Name [5/20]".
+   */
+
+  function buildDetectionId(record) {
+    const bikes = Number.isFinite(record.bikesAvailable)
+      ? record.bikesAvailable
+      : '?';
+    const capacity = Number.isFinite(record.capacity) ? record.capacity : '?';
+    // Render record stores the station name under `stationName` (see the render-map
+    // shape), so `record.name` was always undefined → every label read "Dock N".
+    const label = record.stationName || `Dock ${record.stationId}`;
+    // Truncate long station names to keep HUD readable
+    const short = label.length > 24 ? label.slice(0, 22) + '…' : label;
+    return `🚲 ${short} [${bikes}/${capacity}]`;
+  }
+
+  /**
+   * Collect a sampled subset of visible stations for HUD detection overlay rendering.
+   * Uses a deterministic stride pattern controlled by options.seed and options.maxCount
+   * to avoid overcrowding the HUD while still providing broad coverage.
+   * @param {Object} [options]
+   * @param {number} [options.maxCount] - Maximum number of detectable objects to return.
+   * @param {number} [options.seed] - Seed for deterministic stride offset selection.
+   * @returns {Array<{ position: Cesium.Cartesian3, id: string, type: string, skipLabel: boolean }>}
+   */
+
+  function collectDetectableStations(options = {}) {
+    if (
+      !layerState._enabled ||
+      !layerState._pointCollection ||
+      !layerState._pointCollection.show ||
+      layerState._stationRenderMap.size === 0
+    )
+      return [];
+
+    // Gather all visible station records (include selected even though its point is hidden)
+    const records = [];
+    for (const record of layerState._stationRenderMap.values()) {
+      const isSelected = record.key === layerState._selectedKey;
+      if ((!record.point?.show && !isSelected) || !record.point?.position)
+        continue;
+      records.push(record);
+    }
+    if (records.length === 0) return [];
+
+    // Deterministic subsampling: pick every Nth station, offset by seed
+    const maxCount = Number.isFinite(options.maxCount)
+      ? Math.max(1, Math.floor(options.maxCount))
+      : records.length;
+    const seed = Number.isFinite(options.seed) ? Math.floor(options.seed) : 0;
+    const stride = Math.max(1, Math.ceil(records.length / maxCount));
+    const start = ((seed % stride) + stride) % stride;
+
+    const result = [];
+    for (let i = start; i < records.length; i += stride) {
+      const record = records[i];
+      result.push({
+        position: record.point.position,
+        sourceId: record.key,
+        id: buildDetectionId(record),
+        type: 'VEH',
+        skipLabel: record.key === layerState._selectedKey,
+      });
+      if (result.length >= maxCount) break;
+    }
+
+    return result;
+  }
+  return { buildDetectionId, collectDetectableStations };
+}

src/layers/bikeshare/registry.js

@@ -0,0 +1,394 @@
+function buildBcycleUrls(systemId) {
+  return {
+    stationInformationUrl: `https://gbfs.bcycle.com/${systemId}/station_information.json`,
+    stationStatusUrl: `https://gbfs.bcycle.com/${systemId}/station_status.json`,
+  };
+}
+function bcycleEntry({
+  id,
+  city,
+  centerLat,
+  centerLon,
+  systemId,
+  loadRadiusKm = 100,
+  provider = 'BCycle',
+}) {
+  return {
+    id,
+    city,
+    centerLat,
+    centerLon,
+    loadRadiusKm,
+    provider,
+    ...buildBcycleUrls(systemId),
+  };
+}
+const RAW_GBFS_CITY_REGISTRY = [
+  {
+    id: 'nyc-citibike',
+    city: 'New York, NY',
+    centerLat: 40.7484,
+    centerLon: -73.9967,
+    loadRadiusKm: 140,
+    stationInformationUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/bkn/en/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/bkn/en/station_status.json',
+    provider: 'Citi Bike',
+  },
+  {
+    id: 'chicago-divvy',
+    city: 'Chicago, IL',
+    centerLat: 41.8781,
+    centerLon: -87.6298,
+    loadRadiusKm: 120,
+    stationInformationUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/chi/en/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/chi/en/station_status.json',
+    provider: 'Divvy',
+  },
+  {
+    id: 'dc-capital-bikeshare',
+    city: 'Washington, DC',
+    centerLat: 38.9072,
+    centerLon: -77.0369,
+    loadRadiusKm: 120,
+    stationInformationUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/dca-cabi/en/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/dca-cabi/en/station_status.json',
+    provider: 'Capital Bikeshare',
+  },
+  {
+    id: 'sf-bay-wheels',
+    city: 'San Francisco, CA',
+    centerLat: 37.7749,
+    centerLon: -122.4194,
+    loadRadiusKm: 110,
+    stationInformationUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/bay/en/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.lyft.com/gbfs/2.3/bay/en/station_status.json',
+    provider: 'Bay Wheels',
+  },
+  {
+    id: 'boston-bluebikes',
+    city: 'Boston, MA',
+    centerLat: 42.3601,
+    centerLon: -71.0589,
+    loadRadiusKm: 100,
+    stationInformationUrl:
+      'https://gbfs.bluebikes.com/gbfs/en/station_information.json',
+    stationStatusUrl: 'https://gbfs.bluebikes.com/gbfs/en/station_status.json',
+    provider: 'Blue Bikes',
+  },
+  {
+    id: 'philadelphia-indego',
+    city: 'Philadelphia, PA',
+    centerLat: 39.9526,
+    centerLon: -75.1652,
+    loadRadiusKm: 100,
+    stationInformationUrl:
+      'https://gbfs.bcycle.com/bcycle_indego/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.bcycle.com/bcycle_indego/station_status.json',
+    provider: 'Indego',
+  },
+  {
+    id: 'portland-biketown',
+    city: 'Portland, OR',
+    centerLat: 45.5152,
+    centerLon: -122.6784,
+    loadRadiusKm: 95,
+    stationInformationUrl:
+      'https://gbfs.biketownpdx.com/gbfs/2.3/en/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.biketownpdx.com/gbfs/2.3/en/station_status.json',
+    provider: 'BIKETOWN',
+  },
+  {
+    id: 'la-metro-bike',
+    city: 'Los Angeles, CA',
+    centerLat: 34.0522,
+    centerLon: -118.2437,
+    loadRadiusKm: 120,
+    stationInformationUrl:
+      'https://gbfs.bcycle.com/bcycle_lametro/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.bcycle.com/bcycle_lametro/station_status.json',
+    provider: 'Metro Bike',
+  },
+  {
+    id: 'austin-capmetro',
+    city: 'Austin, TX',
+    centerLat: 30.2672,
+    centerLon: -97.7431,
+    loadRadiusKm: 90,
+    stationInformationUrl:
+      'https://austin.publicbikesystem.net/customer/gbfs/v2/en/station_information.json',
+    stationStatusUrl:
+      'https://austin.publicbikesystem.net/customer/gbfs/v2/en/station_status.json',
+    provider: 'CapMetro',
+  },
+  {
+    id: 'honolulu-biki',
+    city: 'Honolulu, HI',
+    centerLat: 21.3069,
+    centerLon: -157.8583,
+    loadRadiusKm: 90,
+    stationInformationUrl:
+      'https://hon.publicbikesystem.net/customer/gbfs/v2/en/station_information.json',
+    stationStatusUrl:
+      'https://hon.publicbikesystem.net/customer/gbfs/v2/en/station_status.json',
+    provider: 'Biki',
+  },
+  {
+    id: 'columbus-cogo',
+    city: 'Columbus, OH',
+    centerLat: 39.9612,
+    centerLon: -82.9988,
+    loadRadiusKm: 90,
+    stationInformationUrl:
+      'https://gbfs.cogobikeshare.com/gbfs/2.3/en/station_information.json',
+    stationStatusUrl:
+      'https://gbfs.cogobikeshare.com/gbfs/2.3/en/station_status.json',
+    provider: 'CoGo',
+  },
+  {
+    id: 'chattanooga-bikechatt',
+    city: 'Chattanooga, TN',
+    centerLat: 35.0456,
+    centerLon: -85.3097,
+    loadRadiusKm: 90,
+    stationInformationUrl:
+      'https://chat.publicbikesystem.net/customer/gbfs/v2/en/station_information.json',
+    stationStatusUrl:
+      'https://chat.publicbikesystem.net/customer/gbfs/v2/en/station_status.json',
+    provider: 'Bike Chattanooga',
+  },
+  bcycleEntry({
+    id: 'boulder-bcycle',
+    city: 'Boulder, CO',
+    centerLat: 40.015,
+    centerLon: -105.2705,
+    systemId: 'bcycle_boulder',
+  }),
+  bcycleEntry({
+    id: 'milwaukee-bublr',
+    city: 'Milwaukee, WI',
+    centerLat: 43.0389,
+    centerLon: -87.9065,
+    systemId: 'bcycle_bublr',
+    provider: 'Bublr',
+  }),
+  bcycleEntry({
+    id: 'madison-bcycle',
+    city: 'Madison, WI',
+    centerLat: 43.0731,
+    centerLon: -89.4012,
+    systemId: 'bcycle_madison',
+  }),
+  bcycleEntry({
+    id: 'nashville-bcycle',
+    city: 'Nashville, TN',
+    centerLat: 36.1627,
+    centerLon: -86.7816,
+    systemId: 'bcycle_nashville',
+  }),
+  bcycleEntry({
+    id: 'salt-lake-greenbike',
+    city: 'Salt Lake City, UT',
+    centerLat: 40.7608,
+    centerLon: -111.891,
+    systemId: 'bcycle_greenbikeslc',
+    provider: 'GREENbike',
+  }),
+  bcycleEntry({
+    id: 'san-antonio-bcycle',
+    city: 'San Antonio, TX',
+    centerLat: 29.4241,
+    centerLon: -98.4936,
+    systemId: 'bcycle_sanantonio',
+  }),
+  bcycleEntry({
+    id: 'cincinnati-red-bike',
+    city: 'Cincinnati, OH',
+    centerLat: 39.1031,
+    centerLon: -84.512,
+    systemId: 'bcycle_cincyredbike',
+    provider: 'Red Bike',
+  }),
+  bcycleEntry({
+    id: 'el-paso-bcycle',
+    city: 'El Paso, TX',
+    centerLat: 31.7619,
+    centerLon: -106.485,
+    systemId: 'bcycle_elpaso',
+  }),
+  bcycleEntry({
+    id: 'indianapolis-pacers',
+    city: 'Indianapolis, IN',
+    centerLat: 39.7684,
+    centerLon: -86.1581,
+    systemId: 'bcycle_pacersbikeshare',
+    provider: 'Pacers Bikeshare',
+  }),
+  bcycleEntry({
+    id: 'fort-lauderdale-broward',
+    city: 'Fort Lauderdale, FL',
+    centerLat: 26.1224,
+    centerLon: -80.1373,
+    systemId: 'bcycle_broward',
+    provider: 'Broward B-cycle',
+  }),
+  bcycleEntry({
+    id: 'memphis-bcycle',
+    city: 'Memphis, TN',
+    centerLat: 35.1495,
+    centerLon: -90.049,
+    systemId: 'bcycle_memphis',
+  }),
+  bcycleEntry({
+    id: 'des-moines-bcycle',
+    city: 'Des Moines, IA',
+    centerLat: 41.5868,
+    centerLon: -93.625,
+    systemId: 'bcycle_desmoines',
+  }),
+  bcycleEntry({
+    id: 'tucson-tugo',
+    city: 'Tucson, AZ',
+    centerLat: 32.2226,
+    centerLon: -110.9747,
+    systemId: 'bcycle_tugo',
+    provider: 'Tugo',
+  }),
+  bcycleEntry({
+    id: 'fort-worth-trinity',
+    city: 'Fort Worth, TX',
+    centerLat: 32.7555,
+    centerLon: -97.3308,
+    systemId: 'bcycle_fortworth',
+    provider: 'Trinity Metro',
+  }),
+  bcycleEntry({
+    id: 'omaha-heartland',
+    city: 'Omaha, NE',
+    centerLat: 41.2565,
+    centerLon: -95.9345,
+    systemId: 'bcycle_heartland',
+    provider: 'Heartland B-cycle',
+  }),
+  bcycleEntry({
+    id: 'lincoln-bikelnk',
+    city: 'Lincoln, NE',
+    centerLat: 40.8136,
+    centerLon: -96.7026,
+    systemId: 'bcycle_bikelnk',
+    provider: 'BikeLNK',
+  }),
+  bcycleEntry({
+    id: 'greenville-sc-bcycle',
+    city: 'Greenville, SC',
+    centerLat: 34.8526,
+    centerLon: -82.394,
+    systemId: 'bcycle_greenville',
+  }),
+  bcycleEntry({
+    id: 'buffalo-reddy',
+    city: 'Buffalo, NY',
+    centerLat: 42.8864,
+    centerLon: -78.8784,
+    systemId: 'bcycle_reddy',
+    provider: 'Reddy Bikeshare',
+  }),
+  bcycleEntry({
+    id: 'las-vegas-rtc-bike-share',
+    city: 'Las Vegas, NV',
+    centerLat: 36.1699,
+    centerLon: -115.1398,
+    systemId: 'bcycle_rtcbikeshare',
+    provider: 'RTC Bike Share',
+  }),
+  bcycleEntry({
+    id: 'santa-barbara-bcycle',
+    city: 'Santa Barbara, CA',
+    centerLat: 34.4208,
+    centerLon: -119.6982,
+    systemId: 'bcycle_santabarbara',
+  }),
+];
+function normalizeRegistryEntry(entry) {
+  const id = String(entry?.id || '')
+    .trim()
+    .toLowerCase();
+  const city = String(entry?.city || '').trim();
+  const centerLat = Number(entry?.centerLat);
+  const centerLon = Number(entry?.centerLon);
+  const loadRadiusKm = Number(entry?.loadRadiusKm);
+  const stationInformationUrl = new URL(
+    String(entry?.stationInformationUrl || '').trim(),
+  );
+  const stationStatusUrl = new URL(
+    String(entry?.stationStatusUrl || '').trim(),
+  );
+
+  if (!id) throw new Error('GBFS entry id is required');
+  if (!city) throw new Error(`GBFS entry "${id}" city is required`);
+  if (!Number.isFinite(centerLat) || !Number.isFinite(centerLon)) {
+    throw new Error(`GBFS entry "${id}" has invalid center coordinates`);
+  }
+  // Enforce HTTPS-only for GBFS feeds
+  if (
+    stationInformationUrl.protocol !== 'https:' ||
+    stationStatusUrl.protocol !== 'https:'
+  ) {
+    throw new Error(`GBFS entry "${id}" must use https URLs`);
+  }
+  // Validate that URLs end with expected GBFS endpoint filenames
+  if (!/\/station_information\.json$/i.test(stationInformationUrl.pathname)) {
+    throw new Error(`GBFS entry "${id}" station_information URL is invalid`);
+  }
+  if (!/\/station_status\.json$/i.test(stationStatusUrl.pathname)) {
+    throw new Error(`GBFS entry "${id}" station_status URL is invalid`);
+  }
+
+  // Deduplicate hostnames across both feed URLs for proxy allowlisting
+  const hosts = Array.from(
+    new Set([
+      stationInformationUrl.hostname.toLowerCase(),
+      stationStatusUrl.hostname.toLowerCase(),
+    ]),
+  );
+
+  return {
+    id,
+    city,
+    centerLat,
+    centerLon,
+    loadRadiusKm:
+      Number.isFinite(loadRadiusKm) && loadRadiusKm > 0
+        ? loadRadiusKm
+        : CITY_RANGE_BASE_KM,
+    stationInformationUrl: stationInformationUrl.toString(),
+    stationStatusUrl: stationStatusUrl.toString(),
+    provider: String(entry?.provider || 'GBFS').trim() || 'GBFS',
+    hosts,
+  };
+}
+const GBFS_CITY_REGISTRY = (() => {
+  const seen = new Set();
+  return RAW_GBFS_CITY_REGISTRY.map((entry) => {
+    const normalized = normalizeRegistryEntry(entry);
+    if (seen.has(normalized.id)) {
+      throw new Error(`Duplicate GBFS city id: ${normalized.id}`);
+    }
+    seen.add(normalized.id);
+    return normalized;
+  });
+})();
+const CITY_BY_ID = new Map(
+  GBFS_CITY_REGISTRY.map((entry) => [entry.id, entry]),
+);
+export { GBFS_CITY_REGISTRY, CITY_BY_ID };

src/layers/bikeshare/rendering.js

@@ -0,0 +1,282 @@
+import * as Cesium from 'cesium';
+import {
+  DEFAULT_CAPACITY,
+  POINT_SIZE_MIN,
+  POINT_SIZE_MAX,
+  COLOR_NEUTRAL,
+  COLOR_MUTED,
+  COLOR_GREEN,
+  COLOR_YELLOW,
+  COLOR_RED,
+  POINT_HEIGHT_OFFSET_M,
+  MAX_TOTAL_POINTS,
+  COLOR_OUTLINE,
+} from './policy.js';
+
+export function createRendering({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  const { governorRequestRender } = services.render;
+
+  /**
+   * Resolve the effective dock capacity for a station.
+   * Prefers the explicit capacity from station_information; falls back to
+   * bikes+docks from status data; uses DEFAULT_CAPACITY as last resort.
+   * @param {number|null} capacityFromInfo - Capacity from station_information, or null.
+   * @param {Object|null} status - Station status object with bikesAvailable/docksAvailable.
+   * @returns {number} Resolved capacity (always > 0).
+   */
+
+  function resolveCapacity(capacityFromInfo, status) {
+    const fromInfo = parts.model.toNonNegativeInteger(capacityFromInfo);
+    if (fromInfo && fromInfo > 0) return fromInfo;
+
+    // Derive capacity from current bikes + available docks
+    const bikes = parts.model.toNonNegativeInteger(status?.bikesAvailable, 0);
+    const docks = parts.model.toNonNegativeInteger(status?.docksAvailable, 0);
+    const derived = bikes + docks;
+    if (derived > 0) return derived;
+
+    return DEFAULT_CAPACITY;
+  }
+
+  /**
+   * Map station capacity to a point pixel size using a sqrt scale.
+   * Larger-capacity stations render as bigger dots; clamped to [POINT_SIZE_MIN, POINT_SIZE_MAX].
+   * @param {number} capacity - Station dock capacity.
+   * @returns {number} Point size in pixels.
+   */
+
+  function capacityToPixelSize(capacity) {
+    const c = Math.max(1, Math.min(80, Number(capacity) || DEFAULT_CAPACITY));
+    // sqrt scale so large stations don't dominate visually
+    const normalized = Math.sqrt(c) / Math.sqrt(80);
+    const size =
+      POINT_SIZE_MIN + normalized * (POINT_SIZE_MAX - POINT_SIZE_MIN);
+    return Math.max(POINT_SIZE_MIN, Math.min(POINT_SIZE_MAX, size));
+  }
+
+  /**
+   * Determine the display color for a station based on its availability ratio.
+   * - No status data: neutral gray.
+   * - Offline (not installed/renting/returning): muted gray.
+   * - >60% bikes available: green.
+   * - 30-60% bikes available: yellow.
+   * - <30% bikes available: red.
+   * @param {Object|null} status - Station status object.
+   * @param {number} capacity - Resolved station capacity.
+   * @returns {Cesium.Color} Color to apply to the station point.
+   */
+
+  function statusToColor(status, capacity) {
+    if (!status) return COLOR_NEUTRAL;
+    if (!status.isInstalled || !status.isRenting || !status.isReturning)
+      return COLOR_MUTED;
+
+    const bikes = parts.model.toNonNegativeInteger(status.bikesAvailable);
+    if (!Number.isFinite(bikes)) return COLOR_NEUTRAL;
+
+    const cap = Math.max(1, Number(capacity) || DEFAULT_CAPACITY);
+    const ratio = bikes / cap;
+    if (ratio > 0.6) return COLOR_GREEN;
+    if (ratio >= 0.3) return COLOR_YELLOW;
+    return COLOR_RED;
+  }
+
+  /**
+   * Create a Cartesian3 position for a station, terrain-clamped when possible.
+   * Falls back to a fixed small height offset if terrain sampling is unsupported.
+   * @param {Object} station - Station info object with lat/lon.
+   * @returns {Cesium.Cartesian3|null} World position, or null if coordinates are invalid.
+   */
+
+  function createStationPosition(station) {
+    const lon = Number(station?.lon);
+    const lat = Number(station?.lat);
+    if (!Number.isFinite(lat) || !Number.isFinite(lon)) return null;
+
+    let height = POINT_HEIGHT_OFFSET_M;
+    // Sample terrain height so points sit on ground rather than at ellipsoid level
+    if (layerState._viewer?.scene?.sampleHeightSupported) {
+      const carto = Cesium.Cartographic.fromDegrees(lon, lat);
+      const sampled = layerState._viewer.scene.sampleHeight(carto);
+      if (Number.isFinite(sampled)) {
+        height = sampled + POINT_HEIGHT_OFFSET_M;
+      }
+    }
+
+    return Cesium.Cartesian3.fromDegrees(lon, lat, height);
+  }
+
+  /**
+   * Get or create the runtime tracking object for a city.
+   * @param {string} cityId - City identifier.
+   * @returns {{ stationKeys: Set<string> }} City runtime object.
+   */
+
+  function ensureCityRuntime(cityId) {
+    if (layerState._cityRuntime.has(cityId))
+      return layerState._cityRuntime.get(cityId);
+    const runtime = { stationKeys: new Set() };
+    layerState._cityRuntime.set(cityId, runtime);
+    return runtime;
+  }
+
+  /**
+   * Ensure point primitives exist for all stations in a city.
+   * Creates new points for stations not yet rendered; skips existing ones.
+   * Respects the MAX_TOTAL_POINTS global cap to prevent GPU overload.
+   * @param {string} cityId - City identifier.
+   * @param {Map<string, Object>} stationMap - Parsed station info map for the city.
+   */
+
+  function ensureCityPoints(cityId, stationMap) {
+    // Deferred debounce/fetch completions mutate point primitives after the
+    // camera settled — each commit needs one frame in idle mode. (perf wave 2 fix)
+    governorRequestRender('bikeshare-points');
+    const runtime = ensureCityRuntime(cityId);
+
+    for (const station of stationMap.values()) {
+      const key = parts.model.stationKey(cityId, station.stationId);
+      if (layerState._stationRenderMap.has(key)) {
+        runtime.stationKeys.add(key);
+        continue;
+      }
+
+      // Enforce global point cap
+      if (layerState._stationRenderMap.size >= MAX_TOTAL_POINTS) {
+        if (!layerState._limitWarned) {
+          layerState._limitWarned = true;
+          console.warn(
+            `[Data:Bikeshare] Point cap reached (${MAX_TOTAL_POINTS}).`,
+          );
+        }
+        break;
+      }
+
+      const position = createStationPosition(station);
+      if (!position) continue;
+
+      // Add a point primitive with distance-based scale and translucency falloff
+      const point = layerState._pointCollection.add({
+        position,
+        pixelSize: capacityToPixelSize(station.capacity),
+        color: COLOR_NEUTRAL,
+        outlineColor: COLOR_OUTLINE,
+        outlineWidth: 1,
+        scaleByDistance: new Cesium.NearFarScalar(200, 1.35, 130000, 0.4),
+        translucencyByDistance: new Cesium.NearFarScalar(
+          200,
+          1.0,
+          180000,
+          0.15,
+        ),
+        disableDepthTestDistance: 2500,
+        id: key,
+      });
+
+      layerState._stationRenderMap.set(key, {
+        key,
+        cityId,
+        stationId: station.stationId,
+        stationName: station.name,
+        point,
+        capacity: parts.model.toNonNegativeInteger(station.capacity),
+        bikesAvailable: null,
+        docksAvailable: null,
+        isInstalled: station.isInstalled,
+        isRenting: station.isRenting,
+        isReturning: station.isReturning,
+      });
+
+      runtime.stationKeys.add(key);
+    }
+
+    layerState._count = layerState._stationRenderMap.size;
+  }
+
+  /**
+   * Remove all rendered point primitives for a city and clean up runtime state.
+   * Also clears any active selection if it belongs to this city.
+   * @param {string} cityId - City identifier to remove.
+   */
+
+  function removeCityPoints(cityId) {
+    const runtime = layerState._cityRuntime.get(cityId);
+    if (!runtime) return;
+
+    // Clear selection if it belongs to the city being removed
+    if (
+      layerState._selectedKey &&
+      runtime.stationKeys.has(layerState._selectedKey)
+    ) {
+      parts.selection._clearSelection();
+    }
+
+    for (const key of runtime.stationKeys) {
+      const record = layerState._stationRenderMap.get(key);
+      if (!record) continue;
+      layerState._pointCollection.remove(record.point);
+      layerState._stationRenderMap.delete(key);
+    }
+
+    layerState._cityRuntime.delete(cityId);
+    layerState._count = layerState._stationRenderMap.size;
+  }
+
+  /**
+   * Apply real-time status data to rendered station points for a city.
+   * Updates each point's color (availability ratio) and pixel size (capacity),
+   * and refreshes the render record's cached availability fields.
+   * @param {string} cityId - City identifier.
+   * @param {Map<string, Object>} statusMap - Parsed station status map.
+   */
+
+  function applyStatusToPoints(cityId, statusMap) {
+    governorRequestRender('bikeshare-status');
+    const runtime = layerState._cityRuntime.get(cityId);
+    if (!runtime) return;
+
+    for (const key of runtime.stationKeys) {
+      const record = layerState._stationRenderMap.get(key);
+      if (!record) continue;
+
+      const status = statusMap.get(record.stationId) || null;
+      const capacity = resolveCapacity(record.capacity, status);
+      record.capacity = capacity;
+
+      record.bikesAvailable = parts.model.toNonNegativeInteger(
+        status?.bikesAvailable,
+      );
+      record.docksAvailable = parts.model.toNonNegativeInteger(
+        status?.docksAvailable,
+      );
+      record.isInstalled = parts.model.normalizeGbfsBool(
+        status?.isInstalled,
+        true,
+      );
+      record.isRenting = parts.model.normalizeGbfsBool(status?.isRenting, true);
+      record.isReturning = parts.model.normalizeGbfsBool(
+        status?.isReturning,
+        true,
+      );
+
+      // Update visual properties based on current status
+      record.point.pixelSize = capacityToPixelSize(capacity);
+      record.point.color = statusToColor(status, capacity);
+    }
+  }
+  return {
+    resolveCapacity,
+    capacityToPixelSize,
+    statusToColor,
+    createStationPosition,
+    ensureCityRuntime,
+    ensureCityPoints,
+    removeCityPoints,
+    applyStatusToPoints,
+  };
+}

src/layers/bikeshare/selection.js

@@ -0,0 +1,206 @@
+import * as Cesium from 'cesium';
+import {
+  BIKESHARE_SELECTED_OVERLAY_SOURCE_ID,
+  BIKESHARE_SELECTED_OVERLAY_SOURCE_OPTIONS,
+} from './policy.js';
+
+export function createSelection({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  /**
+   * Build a multi-line text label for the selected station popup.
+   * Shows station name, availability counts, and any abnormal operational flags.
+   * @param {Object} record - Render record from _stationRenderMap.
+   * @returns {string} Newline-delimited source text for the selected host card.
+   */
+
+  function buildSelectionLabel(record) {
+    const stationName = String(record?.stationName || '').trim();
+    const stationLabel =
+      stationName ||
+      (record?.stationId ? `Station ${record.stationId}` : 'Station');
+    const bikes = Number.isFinite(record?.bikesAvailable)
+      ? record.bikesAvailable
+      : '?';
+    const docks = Number.isFinite(record?.docksAvailable)
+      ? record.docksAvailable
+      : '?';
+    const capacity = Number.isFinite(record?.capacity) ? record.capacity : '?';
+
+    const lines = [
+      stationLabel,
+      `🚲 ${bikes} avail · ${docks} docks · ${capacity} cap`,
+    ];
+
+    // Append warnings for stations that are offline or partially non-operational
+    const abnormal = [];
+    if (record?.isInstalled === false) abnormal.push('⚠️ Not installed');
+    if (record?.isRenting === false) abnormal.push('⚠️ Not renting');
+    if (record?.isReturning === false) abnormal.push('⚠️ Not returning');
+    if (abnormal.length > 0) {
+      lines.push(abnormal.join(' · '));
+    }
+
+    return lines.join('\n');
+  }
+
+  /**
+   * Build the protected selected-station entry from source-owned copy.
+   * @param {string} key Stable city/station composite key.
+   * @param {Object} record Bikeshare render record.
+   * @returns {Object|null}
+   */
+
+  function createBikeshareSelectedOverlayEntry(key, record) {
+    const position = record?.point?.position;
+    if (!key || !position) return null;
+    const [title, ...details] = buildSelectionLabel(record).split('\n');
+    return {
+      id: String(key),
+      position,
+      variant: 'selected',
+      selected: true,
+      protected: true,
+      paintLane: 'selected',
+      collisionGroup: 'ambient-card',
+      priority: Number.MAX_SAFE_INTEGER,
+      title,
+      details,
+      accent: '#00ffff',
+      interactive: false,
+      anchorRadiusPx: 9,
+      minAnchorGapPx: 11,
+      verticalOnly: true,
+      placement: 'above',
+      edgeFade: 'keyhole',
+      horizonCull: true,
+      terrainOcclusion: false,
+    };
+  }
+
+  /**
+   * Clear the current station selection.
+   * Re-shows the hidden point primitive and removes the highlight entity.
+   */
+
+  function _clearSelection() {
+    if (layerState._selectedKey) {
+      const record = layerState._stationRenderMap.get(layerState._selectedKey);
+      if (record?.point) {
+        record.point.show = true;
+      }
+    }
+
+    if (layerState._selectedEntity && layerState._viewer) {
+      layerState._viewer.entities.remove(layerState._selectedEntity);
+    }
+
+    layerState._selectedKey = null;
+    layerState._selectedEntity = null;
+    layerState._overlayHost.clearSource(BIKESHARE_SELECTED_OVERLAY_SOURCE_ID);
+  }
+
+  /**
+   * Select a station by key: hides the original point primitive and adds a
+   * highlighted cyan entity plus a protected shared-host availability card.
+   * @param {string} key - Composite "cityId:stationId" key.
+   */
+
+  function _selectStation(key) {
+    _clearSelection();
+
+    const record = layerState._stationRenderMap.get(key);
+    if (!record || !record.point?.position || !layerState._viewer) return;
+
+    layerState._selectedKey = key;
+    // Hide the base point so the highlight entity replaces it visually
+    record.point.show = false;
+
+    layerState._selectedEntity = layerState._viewer.entities.add({
+      position: record.point.position,
+      point: {
+        pixelSize: 14,
+        color: Cesium.Color.CYAN,
+        outlineColor: Cesium.Color.BLACK,
+        outlineWidth: 2,
+        disableDepthTestDistance: Number.POSITIVE_INFINITY,
+      },
+    });
+    const entry = createBikeshareSelectedOverlayEntry(key, record);
+    if (entry) {
+      layerState._overlayHost.setEntries(
+        BIKESHARE_SELECTED_OVERLAY_SOURCE_ID,
+        [entry],
+        BIKESHARE_SELECTED_OVERLAY_SOURCE_OPTIONS,
+      );
+    }
+  }
+
+  /**
+   * Install a screen-space click handler for station selection/deselection.
+   * Also registers a global keydown listener for Escape-to-deselect.
+   * Idempotent — does nothing if a handler is already installed.
+   * @param {Cesium.Viewer} viewer - Cesium viewer instance.
+   */
+
+  function _installClickHandler(viewer) {
+    if (layerState._clickHandler) return;
+
+    layerState._clickHandler = new Cesium.ScreenSpaceEventHandler(
+      viewer.scene.canvas,
+    );
+    layerState._clickHandler.setInputAction((click) => {
+      const picked = viewer.scene.pick(click.position);
+
+      if (picked) {
+        // Clicking selected entity itself — ignore (don't deselect).
+        if (picked.id === layerState._selectedEntity) return;
+
+        // Check if the picked primitive or entity id matches a station key
+        const primitive = picked.primitive;
+        if (
+          primitive &&
+          typeof primitive.id === 'string' &&
+          layerState._stationRenderMap.has(primitive.id)
+        ) {
+          _selectStation(primitive.id);
+          return;
+        }
+        if (
+          typeof picked.id === 'string' &&
+          layerState._stationRenderMap.has(picked.id)
+        ) {
+          _selectStation(picked.id);
+          return;
+        }
+      }
+
+      // Clicked empty space — deselect.
+      if (layerState._selectedKey) _clearSelection();
+    }, Cesium.ScreenSpaceEventType.LEFT_CLICK);
+
+    document.addEventListener('keydown', _onKeyDown);
+  }
+
+  /**
+   * Global keydown handler — deselects the current station on Escape.
+   * @param {KeyboardEvent} e - Keyboard event.
+   */
+
+  function _onKeyDown(e) {
+    if (e.key === 'Escape' && layerState._selectedKey) {
+      _clearSelection();
+    }
+  }
+  return {
+    buildSelectionLabel,
+    createBikeshareSelectedOverlayEntry,
+    _clearSelection,
+    _selectStation,
+    _installClickHandler,
+    _onKeyDown,
+  };
+}

src/layers/bikeshare/source.js

@@ -0,0 +1,23 @@
+/** Read a GBFS station document through the existing bounded server proxy. */
+export function createBikeshareSource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+} = {}) {
+  return {
+    async getStations(upstreamUrl, { signal } = {}) {
+      const url = new URL(upstreamUrl);
+      if (url.protocol !== 'https:' || url.username || url.password || url.hash)
+        throw new TypeError('A public HTTPS GBFS URL is required');
+      signal?.throwIfAborted();
+      const response = await fetchImpl(
+        '/api/gbfs?url=' + encodeURIComponent(url.href),
+        { method: 'GET', headers: { Accept: 'application/json' }, signal },
+      );
+      if (!response.ok) throw new Error('GBFS HTTP ' + response.status);
+      const payload = await response.json();
+      signal?.throwIfAborted();
+      if (!payload || typeof payload !== 'object')
+        throw new Error('Malformed GBFS payload');
+      return payload;
+    },
+  };
+}

src/layers/bikeshare/source.test.mjs

@@ -0,0 +1,44 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { createBikeshareSource } from './source.js';
+test('station source keeps upstream URLs behind the fixed GBFS endpoint', async () => {
+  const calls = [];
+  const source = createBikeshareSource({
+    fetchImpl: async (...args) => {
+      calls.push(args);
+      return new Response('{"data":{"stations":[]}}');
+    },
+  });
+  for (const url of [
+    'file:///etc/passwd',
+    'http://example.test/stations',
+    'https://user:[email protected]/stations',
+  ])
+    await assert.rejects(source.getStations(url), /HTTPS GBFS/);
+  assert.equal(calls.length, 0);
+  await source.getStations('https://example.test/stations.json');
+  const url = new URL(calls[0][0], 'https://app.example');
+  assert.equal(url.pathname, '/api/gbfs');
+  assert.equal(
+    url.searchParams.get('url'),
+    'https://example.test/stations.json',
+  );
+});
+test('cancelled station parsing never publishes the response', async () => {
+  const controller = new AbortController();
+  const source = createBikeshareSource({
+    fetchImpl: async () => ({
+      ok: true,
+      json: async () => {
+        controller.abort();
+        return { data: { stations: [] } };
+      },
+    }),
+  });
+  await assert.rejects(
+    source.getStations('https://example.test/stations', {
+      signal: controller.signal,
+    }),
+    { name: 'AbortError' },
+  );
+});

src/layers/bikeshare/state.js

@@ -0,0 +1,110 @@
+export function createState({ services }) {
+  const { setOverlayEntries, setOverlaySourceVisible, clearOverlaySource } =
+    services.overlays;
+  const layerState = {};
+
+  layerState.DEFAULT_OVERLAY_HOST = Object.freeze({
+    setEntries: setOverlayEntries,
+    setVisible: setOverlaySourceVisible,
+    clearSource: clearOverlaySource,
+  });
+
+  layerState._overlayHost = layerState.DEFAULT_OVERLAY_HOST;
+
+  // ---------------------------------------------------------------------------
+  // Module-level mutable state
+  // ---------------------------------------------------------------------------
+
+  /** @type {Cesium.Viewer|null} Active Cesium viewer instance. */
+
+  layerState._viewer = null;
+
+  /** @type {Cesium.PointPrimitiveCollection|null} Primitive collection for station dots. */
+
+  layerState._pointCollection = null;
+
+  /** Whether the bikeshare layer is currently enabled. */
+
+  layerState._enabled = false;
+
+  /** Timer handle for camera-move debounce. */
+
+  layerState._cameraDebounceTimer = null;
+
+  /** Whether the camera.changed listener is currently attached. */
+
+  layerState._cameraChangedAttached = false;
+
+  /** Hysteresis flag for altitude-based activation. */
+
+  layerState._altitudeGateEnabled = false;
+
+  /** Monotonic generation counter; incremented on each proximity check to cancel stale work. */
+
+  layerState._proximityGeneration = 0;
+
+  /** @type {Set<string>} City ids currently considered in-range. */
+
+  layerState._activeCityIds = new Set();
+
+  /** @type {Map<string, { stationKeys: Set<string> }>} Per-city runtime tracking of rendered station keys. */
+
+  layerState._cityRuntime = new Map();
+
+  /** @type {Map<string, Map<string, Object>>} Cached station information per city (cityId -> stationId -> StationInfo). */
+
+  layerState._stationInfoCache = new Map();
+
+  /** @type {Map<string, { timestamp: number, statusMap: Map<string, Object> }>} Cached station status per city. */
+
+  layerState._statusCache = new Map();
+
+  /** @type {Map<string, { promise: Promise, controller: AbortController, generation: number }>} In-flight station info requests. */
+
+  layerState._inFlightInfo = new Map();
+
+  /** @type {Map<string, { promise: Promise, controller: AbortController, generation: number }>} In-flight station status requests. */
+
+  layerState._inFlightStatus = new Map();
+
+  /** @type {Map<string, Object>} Render records keyed by "cityId:stationId". */
+
+  layerState._stationRenderMap = new Map();
+
+  /** @type {Cesium.ScreenSpaceEventHandler|null} Click handler for station selection. */
+
+  layerState._clickHandler = null;
+
+  /** @type {string|null} Key of the currently selected station, or null. */
+
+  layerState._selectedKey = null;
+
+  /** @type {Cesium.Entity|null} Entity used to display the selected-station point highlight. */
+
+  layerState._selectedEntity = null;
+
+  /** Total number of currently rendered station points. */
+
+  layerState._count = 0;
+
+  /** Timestamp (ms) of the last successful status update. */
+
+  layerState._lastUpdate = null;
+
+  /** Whether any GBFS fetch is currently in progress. */
+
+  layerState._loading = false;
+
+  /** Reference count of concurrent loading operations. */
+
+  layerState._loadingOps = 0;
+
+  /** Most recent error message string, or null. */
+
+  layerState._error = null;
+
+  /** Whether the MAX_TOTAL_POINTS cap warning has already been logged. */
+
+  layerState._limitWarned = false;
+  return layerState;
+}

src/layers/bikeshare/testing.js

@@ -0,0 +1,34 @@
+export function createTesting({ state: layerState, services, parts, source }) {
+  /** Seed a selected-station runtime record while still exercising real select/clear paths. */
+
+  function _setBikeshareSelectionStateForTest({
+    viewer,
+    key,
+    record,
+    overlayHost,
+  }) {
+    layerState._viewer = viewer;
+    layerState._stationRenderMap = new Map([[key, record]]);
+    layerState._selectedKey = null;
+    layerState._selectedEntity = null;
+    layerState._overlayHost = overlayHost || layerState.DEFAULT_OVERLAY_HOST;
+  }
+
+  /** Exercise the production selection path in focused runtime tests. */
+
+  function _selectBikeshareStationForTest(key) {
+    parts.selection._selectStation(key);
+  }
+
+  /** Exercise the production clear path and restore the production host seam. */
+
+  function _clearBikeshareSelectionForTest() {
+    parts.selection._clearSelection();
+    layerState._overlayHost = layerState.DEFAULT_OVERLAY_HOST;
+  }
+  return {
+    _setBikeshareSelectionStateForTest,
+    _selectBikeshareStationForTest,
+    _clearBikeshareSelectionForTest,
+  };
+}

src/layers/bikeshare/viewport.js

@@ -0,0 +1,257 @@
+import * as Cesium from 'cesium';
+import { GBFS_CITY_REGISTRY } from './registry.js';
+import {
+  ACTIVATION_EXIT_ALTITUDE_M,
+  ACTIVATION_ENTER_ALTITUDE_M,
+  CITY_RANGE_BASE_KM,
+  CAMERA_DEBOUNCE_MS,
+} from './policy.js';
+
+export function createViewport({ state: layerState, services, parts, source }) {
+  const { governorRequestRender } = services.render;
+
+  /**
+   * Get the camera's current altitude in meters above the ellipsoid.
+   * @param {Cesium.Viewer} viewer - Cesium viewer instance.
+   * @returns {number} Altitude in meters, or Infinity if unavailable.
+   */
+
+  function getCameraAltitude(viewer) {
+    const carto = viewer?.camera?.positionCartographic;
+    return carto && Number.isFinite(carto.height) ? carto.height : Infinity;
+  }
+
+  /**
+   * Determine the lat/lon the camera is currently looking at.
+   * Prefers the center of the computed view rectangle; falls back to the
+   * camera's own cartographic position when the rectangle is unavailable.
+   * @param {Cesium.Viewer} viewer - Cesium viewer instance.
+   * @returns {{ lat: number, lon: number }|null} Center coordinates in degrees, or null.
+   */
+
+  function getCameraCenterLatLon(viewer) {
+    // Try view rectangle center first (more accurate for tilted views)
+    const rect = viewer?.camera?.computeViewRectangle?.(
+      viewer.scene.globe?.ellipsoid,
+    );
+    if (rect) {
+      const center = Cesium.Rectangle.center(rect);
+      return {
+        lat: Cesium.Math.toDegrees(center.latitude),
+        lon: Cesium.Math.toDegrees(center.longitude),
+      };
+    }
+
+    // Fallback: use the camera's own position
+    const carto = viewer?.camera?.positionCartographic;
+    if (carto) {
+      return {
+        lat: Cesium.Math.toDegrees(carto.latitude),
+        lon: Cesium.Math.toDegrees(carto.longitude),
+      };
+    }
+
+    return null;
+  }
+
+  /**
+   * Determine whether the layer should be active at the given camera altitude.
+   * Uses hysteresis (separate enter/exit thresholds) to avoid rapid toggling
+   * when the camera hovers near the activation boundary.
+   * @param {number} altitude - Camera altitude in meters.
+   * @returns {boolean} True if the layer should remain/become active.
+   */
+
+  function shouldActivateAtAltitude(altitude) {
+    if (!Number.isFinite(altitude)) {
+      layerState._altitudeGateEnabled = false;
+      return false;
+    }
+    if (layerState._altitudeGateEnabled) {
+      // Deactivate only after crossing the higher exit threshold
+      if (altitude >= ACTIVATION_EXIT_ALTITUDE_M)
+        layerState._altitudeGateEnabled = false;
+    } else if (altitude <= ACTIVATION_ENTER_ALTITUDE_M) {
+      // Activate when dropping below the lower enter threshold
+      layerState._altitudeGateEnabled = true;
+    }
+    return layerState._altitudeGateEnabled;
+  }
+
+  /**
+   * Determine which cities are close enough to the camera to warrant loading.
+   * Compares haversine distance from the camera center to each city's center
+   * against the city's configured load radius.
+   * @param {{ lat: number, lon: number }} center - Camera center in degrees.
+   * @returns {Set<string>} Set of city ids currently within load range.
+   */
+
+  function computeInRangeCities(center) {
+    const active = new Set();
+    if (!center) return active;
+
+    for (const city of GBFS_CITY_REGISTRY) {
+      const distance = parts.model.haversineKm(
+        center.lat,
+        center.lon,
+        city.centerLat,
+        city.centerLon,
+      );
+      const radius = Math.max(CITY_RANGE_BASE_KM, city.loadRadiusKm);
+      if (distance <= radius) active.add(city.id);
+    }
+
+    return active;
+  }
+
+  /**
+   * Fully deactivate a single city: abort pending fetches and remove rendered points.
+   * @param {string} cityId - City identifier to deactivate.
+   */
+
+  function deactivateCity(cityId) {
+    governorRequestRender('bikeshare-deactivate');
+    parts.ingestion.abortInFlight(layerState._inFlightInfo, cityId);
+    parts.ingestion.abortInFlight(layerState._inFlightStatus, cityId);
+    parts.rendering.removeCityPoints(cityId);
+  }
+
+  /** Deactivate all currently active cities and clear the active set. */
+
+  function deactivateAllCities() {
+    const cityIds = Array.from(layerState._activeCityIds);
+    for (const cityId of cityIds) deactivateCity(cityId);
+    layerState._activeCityIds.clear();
+  }
+
+  /**
+   * Activate a city: fetch station info, create point primitives, fetch status,
+   * and apply availability colors. Checks generation at each async boundary
+   * to bail out if the proximity context has changed.
+   * @param {string} cityId - City identifier to activate.
+   * @param {number} generation - Proximity generation at time of invocation.
+   */
+
+  async function activateCity(cityId, generation) {
+    if (!layerState._enabled || !layerState._activeCityIds.has(cityId)) return;
+
+    try {
+      const stationMap = await parts.ingestion.loadCityStationInfo(
+        cityId,
+        generation,
+      );
+      // Bail if context changed during fetch
+      if (
+        !layerState._enabled ||
+        !layerState._activeCityIds.has(cityId) ||
+        generation !== layerState._proximityGeneration
+      )
+        return;
+
+      parts.rendering.ensureCityPoints(cityId, stationMap);
+
+      // Apply any cached status immediately for snappier initial rendering
+      const cachedStatus = layerState._statusCache.get(cityId)?.statusMap;
+      if (cachedStatus) {
+        parts.rendering.applyStatusToPoints(cityId, cachedStatus);
+      }
+
+      const statusMap = await parts.ingestion.loadCityStationStatus(
+        cityId,
+        generation,
+      );
+      if (
+        !layerState._enabled ||
+        !layerState._activeCityIds.has(cityId) ||
+        generation !== layerState._proximityGeneration
+      )
+        return;
+      parts.rendering.applyStatusToPoints(cityId, statusMap);
+      layerState._lastUpdate = Date.now();
+      layerState._error = null;
+    } catch (error) {
+      if (error?.name === 'AbortError') return;
+      console.warn(`[Data:Bikeshare] ${cityId} activate error:`, error);
+      layerState._error = 'GBFS fetch error';
+      deactivateCity(cityId);
+      layerState._activeCityIds.delete(cityId);
+    } finally {
+      layerState._count = layerState._stationRenderMap.size;
+    }
+  }
+
+  /**
+   * Core proximity check: determines which cities are in camera range at the
+   * current altitude, deactivates out-of-range cities, and activates newly
+   * in-range ones. Increments the generation counter to invalidate stale work.
+   * @returns {Promise<void>}
+   */
+
+  async function runProximityCheck() {
+    if (!layerState._enabled || !layerState._viewer) return;
+
+    const generation = ++layerState._proximityGeneration;
+    const altitude = getCameraAltitude(layerState._viewer);
+    // Altitude gate: disable all cities when camera is too high
+    if (!shouldActivateAtAltitude(altitude)) {
+      deactivateAllCities();
+      return;
+    }
+
+    const center = getCameraCenterLatLon(layerState._viewer);
+    if (!center) return;
+
+    // Diff active set against newly computed in-range set
+    const nextActive = computeInRangeCities(center);
+    for (const cityId of layerState._activeCityIds) {
+      if (!nextActive.has(cityId)) {
+        deactivateCity(cityId);
+      }
+    }
+
+    layerState._activeCityIds = nextActive;
+    if (layerState._activeCityIds.size === 0) {
+      layerState._count = 0;
+      return;
+    }
+
+    // Only activate cities that don't already have rendered points
+    const toActivate = [];
+    for (const cityId of layerState._activeCityIds) {
+      if (!layerState._cityRuntime.has(cityId)) toActivate.push(cityId);
+    }
+    if (toActivate.length === 0) return;
+
+    await Promise.all(
+      toActivate.map((cityId) => activateCity(cityId, generation)),
+    );
+  }
+
+  /** Schedule a debounced proximity check after camera movement. */
+
+  function scheduleProximityCheck() {
+    clearTimeout(layerState._cameraDebounceTimer);
+    layerState._cameraDebounceTimer = setTimeout(() => {
+      void runProximityCheck();
+    }, CAMERA_DEBOUNCE_MS);
+  }
+
+  /** Camera change event handler — triggers a debounced proximity check. */
+
+  function onCameraChanged() {
+    if (!layerState._enabled) return;
+    scheduleProximityCheck();
+  }
+  return {
+    getCameraAltitude,
+    getCameraCenterLatLon,
+    shouldActivateAtAltitude,
+    computeInRangeCities,
+    deactivateCity,
+    deactivateAllCities,
+    activateCity,
+    runProximityCheck,
+    scheduleProximityCheck,
+    onCameraChanged,
+  };
+}

src/layers/traffic/animation.js

@@ -0,0 +1,314 @@
+import { flowBucket, flowSpeedScale } from '../../data/trafficFlowStyle.js';
+import { presetDotOutline } from '../../data/trafficPresetStyle.js';
+import * as Cesium from 'cesium';
+import { queuePlatoons, locateAlongRoad } from '../../data/trafficQueue.js';
+import {
+  SPEED_MPS,
+  MAX_DOTS,
+  JAM_DOT_FAR_SCALE,
+  JAM_DOT_DEPTH_PUNCH,
+  CREEP_MOVE_MS,
+  CREEP_STOP_MS,
+  CREEP_BURST,
+  HEAT_JAM_BASE_ALPHA,
+  HEAT_JAM_PULSE_ALPHA,
+} from './policy.js';
+
+export function createAnimation({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  /**
+   * Spawn animated dot primitives along a single road.
+   *
+   * Each dot is placed at a random position along the road, assigned a
+   * randomized speed (base +/-30%), and given a direction (alternating
+   * forward/backward to simulate two-way traffic).
+   *
+   * @param {{waypoints:Cesium.Cartesian3[], segmentDist:number[], type:string, coords:number[][]}} road
+   *   Parsed road object with pre-computed waypoints.
+   * @param {number} altitude      - Camera altitude (used if budgetCount is null).
+   * @param {number|null} [budgetCount=null] - Pre-allocated dot count. Falls back
+   *   to `computeDotCount` when null.
+   */
+
+  function spawnDotsForRoad(road, altitude, budgetCount = null) {
+    // Live flow styling (`road.flow` only exists in live mode; keyless path is
+    // byte-identical): closures spawn nothing, congestion colors/slows dots.
+    const flow = layerState._liveMode ? road.flow : null;
+    if (flow?.closure) return;
+    if (layerState._liveMode && !flow && layerState._uncoveredMode === 'hide')
+      return;
+
+    const count = Number.isFinite(budgetCount)
+      ? Math.max(0, Math.floor(budgetCount))
+      : parts.model.computeDotCount(road, altitude);
+    const numSegments = road.waypoints.length - 1;
+    if (numSegments < 1 || count <= 0) return;
+
+    const baseMps = SPEED_MPS[road.type] || 5;
+    const bucket = flow ? flowBucket(flow.level) : null;
+    // Jam dots get +1px: a red queue should read as a queue at a glance.
+    // Preset-aware styling adds its own size delta and floors the base (0 /
+    // no floor under the normal profile) so NVG/FLIR/CRT dots stay PRESENT.
+    const pixelSize =
+      parts.style.baseDotSize(road.type, bucket) +
+      (bucket === 'jam' ? 1 : 0) +
+      parts.style.activeSizeDelta(bucket);
+    const flowColor = bucket ? layerState._activeBucketColors[bucket] : null;
+    // Dark-halo outline under styled presets (null = shipped no-outline).
+    const outlineSpec =
+      bucket && layerState._presetDots === 'on'
+        ? presetDotOutline(layerState._stylePreset, bucket)
+        : null;
+    const outlineColor = outlineSpec
+      ? new Cesium.Color(
+          outlineSpec.rgba[0] / 255,
+          outlineSpec.rgba[1] / 255,
+          outlineSpec.rgba[2] / 255,
+          outlineSpec.rgba[3],
+        )
+      : null;
+    const flowSpeed = flow ? flowSpeedScale(flow.level) : 1;
+    const now = Date.now();
+
+    // Jam-viz density prototype: jam-road dots spawn as bumper-to-bumper
+    // platoons (one shared direction per queue) instead of uniform scatter.
+    // Unreachable in sim mode — `bucket` requires flow.
+    let placements = null;
+    if (bucket === 'jam' && parts.style.jamDensityOn()) {
+      let totalLen = 0;
+      for (const d of road.segmentDist) totalLen += d;
+      const platoons = queuePlatoons(totalLen, count);
+      if (platoons.length) {
+        placements = [];
+        for (let p = 0; p < platoons.length; p++) {
+          const dir = road.oneway ? road.oneway : p % 2 === 0 ? 1 : -1;
+          for (const s of platoons[p]) {
+            const { segIdx, t } = locateAlongRoad(road.segmentDist, s);
+            placements.push({ segIdx, t, direction: dir });
+          }
+        }
+      }
+    }
+
+    for (let i = 0; i < count; i++) {
+      if (layerState._dots.length >= MAX_DOTS) return;
+
+      // Random start position: pick a random segment and offset within it —
+      // unless this is a queued jam dot with a platoon placement.
+      const segIdx = placements
+        ? placements[i].segIdx
+        : Math.floor(Math.random() * numSegments);
+      const t = placements ? placements[i].t : Math.random();
+
+      // Speed noise: base speed +/-30% for organic variation. baseMps (noise
+      // included, flow excluded) is kept on the dot so a late-arriving flow
+      // match can rescale speed in place (recolorDotsInPlace).
+      const noisedMps =
+        baseMps * layerState._speedScale * (0.7 + Math.random() * 0.6);
+      const mps = noisedMps * flowSpeed;
+
+      // One-way roads flow only their legal direction; two-way alternates
+      // (per platoon in queue mode — a queue moves as one).
+      const direction = placements
+        ? placements[i].direction
+        : road.oneway
+          ? road.oneway
+          : i % 2 === 0
+            ? 1
+            : -1;
+
+      // Compute initial Cartesian3 position via linear interpolation
+      Cesium.Cartesian3.lerp(
+        road.waypoints[segIdx],
+        road.waypoints[segIdx + 1],
+        t,
+        layerState._scratchLerp,
+      );
+
+      // Jam-viz density prototype: jam dots stay visible at city scale — a
+      // longer depth-test punch-through (single-sample road heights sit under
+      // the mesh at oblique views) and a higher far-scale floor. Sim dots and
+      // other buckets keep the shipped values.
+      const jamProminent = bucket === 'jam' && parts.style.jamDensityOn();
+      const point = layerState._pointCollection.add({
+        position: Cesium.Cartesian3.clone(layerState._scratchLerp),
+        pixelSize,
+        // No flow data → today's exact simulated white.
+        color: flowColor || Cesium.Color.WHITE.withAlpha(0.85),
+        scaleByDistance: new Cesium.NearFarScalar(
+          100,
+          1.5,
+          layerState._fadeScaleFar,
+          jamProminent ? JAM_DOT_FAR_SCALE : 0.3,
+        ),
+        translucencyByDistance: new Cesium.NearFarScalar(
+          100,
+          1.0,
+          layerState._fadeTransFar,
+          0.0,
+        ),
+        // visible through tiles only when very close (jam: city-scale punch)
+        disableDepthTestDistance: jamProminent ? JAM_DOT_DEPTH_PUNCH : 2000,
+        // Preset dark halo (spread only when present — the keyless/normal
+        // path passes the exact shipped option set).
+        ...(outlineSpec
+          ? { outlineColor, outlineWidth: outlineSpec.width }
+          : {}),
+      });
+      layerState._bucketCounts[bucket || 'sim'] += 1;
+
+      layerState._dots.push({
+        point,
+        road,
+        bucket, // flow bucket at spawn (null = sim) — drives preset restyle/pulse
+        waypoints: road.waypoints,
+        segmentDist: road.segmentDist,
+        numSegments,
+        segIdx,
+        t,
+        mps, // meters per second (flow-scaled)
+        baseMps: noisedMps, // pre-flow speed, for in-place flow rescale
+        direction,
+        stoppedUntil: 0,
+        // Stop-and-go creep state (jam-viz density prototype): jam dots
+        // alternate move-bursts and stops. Null in sim mode and for non-jam.
+        creep:
+          bucket === 'jam' && parts.style.jamDensityOn()
+            ? { moving: Math.random() < 0.4, until: now + Math.random() * 2000 }
+            : null,
+      });
+    }
+  }
+
+  /**
+   * Per-frame animation callback registered on `scene.preRender`.
+   *
+   * For every active dot:
+   *  1. Skip if currently paused by a simulated stop-light.
+   *  2. Convert speed (m/s) to a parametric t-delta relative to the current
+   *     segment's Cartesian distance.
+   *  3. Advance t in the dot's travel direction, handling segment boundary
+   *     crossings and end-of-road reversals.
+   *  4. Linearly interpolate between the two bounding waypoints and update the
+   *     point primitive's position.
+   *
+   * Delta time is capped at 100 ms to prevent large jumps after background tabs.
+   */
+
+  function animate() {
+    const now = Date.now();
+    // Delta time in seconds, capped to avoid jumps when returning from background tab
+    const dt = layerState._lastAnimTime
+      ? Math.min((now - layerState._lastAnimTime) / 1000, 0.1)
+      : 0.016;
+    layerState._lastAnimTime = now;
+
+    for (let i = 0; i < layerState._dots.length; i++) {
+      const dot = layerState._dots[i];
+
+      // Simulated stop-light pause — skip movement while timer is active
+      if (now < dot.stoppedUntil) continue;
+
+      // Stop-and-go creep (jam-viz density prototype, live jam dots only):
+      // alternate short forward bursts with stops. The burst multiplier keeps
+      // the long-run average near the honest TomTom crawl speed.
+      let burst = 1;
+      if (dot.creep) {
+        if (now >= dot.creep.until) {
+          dot.creep.moving = !dot.creep.moving;
+          const [lo, hi] = dot.creep.moving ? CREEP_MOVE_MS : CREEP_STOP_MS;
+          dot.creep.until = now + lo + Math.random() * (hi - lo);
+        }
+        if (!dot.creep.moving) continue;
+        burst = CREEP_BURST;
+      }
+
+      // Convert m/s speed to parametric t-delta for the current segment length
+      const segLen = dot.segmentDist[dot.segIdx] || 1;
+      const tDelta = (dot.mps * burst * dt) / segLen;
+
+      // Advance parametric position along the road in the current direction
+      dot.t += tDelta * dot.direction;
+
+      // Handle forward segment boundary crossing (t >= 1.0)
+      if (dot.t >= 1.0) {
+        dot.t -= 1.0;
+        dot.segIdx++;
+        if (dot.segIdx >= dot.numSegments) {
+          // End of road: recycle to the road's entry with a small stagger —
+          // cars don't reverse at the end of a street (field-test round 1).
+          // Direction is preserved, so one-way flow stays legal.
+          dot.segIdx = 0;
+          dot.t = Math.random() * 0.3;
+        }
+        maybeStopLight(dot, now);
+      } else if (dot.t <= 0.0) {
+        // Handle backward segment boundary crossing (t <= 0.0)
+        dot.t += 1.0;
+        dot.segIdx--;
+        if (dot.segIdx < 0) {
+          // Start of road (traveling backward): recycle to the far end.
+          dot.segIdx = dot.numSegments - 1;
+          dot.t = 1.0 - Math.random() * 0.3;
+        }
+        maybeStopLight(dot, now);
+      }
+
+      // Lerp between pre-computed Cartesian3 waypoints (no trig needed).
+      // Pass the scratch directly: PointPrimitive's position setter clones the
+      // value into its own storage (and skips the VBO dirty flag when equal), so
+      // the extra defensive clone here allocated 360–720k Cartesian3/s of pure
+      // garbage across 6000 dots. (perf item 5)
+      const a = dot.waypoints[dot.segIdx];
+      const b = dot.waypoints[dot.segIdx + 1];
+      Cesium.Cartesian3.lerp(a, b, dot.t, layerState._scratchLerp);
+      dot.point.position = layerState._scratchLerp;
+    }
+
+    // Jam heat-lines throb (~1.6 s period) — one shared material uniform for
+    // the whole jam batch, no geometry rebuild. Null outside live heatline mode.
+    if (layerState._heatJamPrim?.appearance) {
+      layerState._heatJamPrim.appearance.material.uniforms.color.alpha =
+        HEAT_JAM_BASE_ALPHA + HEAT_JAM_PULSE_ALPHA * Math.sin(now / 260);
+    }
+
+    layerState._animFrame++;
+  }
+
+  /**
+   * Randomly pause a dot near road endpoints to simulate stop-light behaviour.
+   *
+   * Only triggers within the first 2 or last 2 segments of the road, and only
+   * with a very low per-frame probability (0.8%) to keep traffic flowing.
+   *
+   * @param {Object} dot - The dot state object.
+   * @param {number} now - Current timestamp in milliseconds.
+   */
+
+  function maybeStopLight(dot, now) {
+    const nearEnd = dot.segIdx <= 1 || dot.segIdx >= dot.numSegments - 2;
+    if (nearEnd && Math.random() < 0.008) {
+      // Pause for 2–6 seconds
+      dot.stoppedUntil = now + 2000 + Math.random() * 4000;
+    }
+  }
+
+  // ─── Cleanup ───────────────────────────────────────────────
+
+  /** Remove all point primitives and reset dot/road arrays and counters. */
+
+  function clearDots() {
+    if (layerState._pointCollection) layerState._pointCollection.removeAll();
+    parts.rendering.removeHeatLines();
+    layerState._dots = [];
+    layerState._roads = [];
+    layerState._count = 0;
+    layerState._bucketCounts = { free: 0, slow: 0, jam: 0, sim: 0 };
+    layerState._closedRoads = 0;
+  }
+  return { spawnDotsForRoad, animate, maybeStopLight, clearDots };
+}

src/layers/traffic/controls.js

@@ -0,0 +1,189 @@
+import {
+  trafficBucketTier,
+  trafficStyleProfile,
+} from '../../data/trafficPresetStyle.js';
+import { TRAFFIC_TIMING_ENABLED } from './policy.js';
+
+export function createControls({ state: layerState, services, parts, source }) {
+  const { getFlowSessionStats } = source;
+
+  const methods = {
+    id: 'traffic',
+
+    name: 'Street Traffic',
+
+    icon: '🚗',
+
+    source: 'OpenStreetMap',
+
+    /** @type {number} Zero — layer is self-managed via camera listener + preRender */
+    updateInterval: 0,
+
+    /**
+     * Update user-adjustable parameters (density and speed scaling).
+     *
+     * @param {Object}  [params]
+     * @param {number}  [params.densityScale] - Dot density multiplier (clamped 0.2–2.5).
+     * @param {number}  [params.speedScale]   - Dot speed multiplier (clamped 0.3–3.0).
+     */
+    setParams(params = {}) {
+      if (typeof params.densityScale === 'number') {
+        layerState._densityScale = Math.max(
+          0.2,
+          Math.min(2.5, params.densityScale),
+        );
+      }
+      if (typeof params.speedScale === 'number') {
+        layerState._speedScale = Math.max(
+          0.3,
+          Math.min(3.0, params.speedScale),
+        );
+      }
+      // Live-mode treatment of roads TomTom has no flow data for:
+      // 'sim' (default) keeps them as today's white ambient dots — colored =
+      // real data, white = simulation; 'hide' spawns nothing on them (strict
+      // data-integrity view). Owner-explorable; re-render applies on the next
+      // camera-driven load.
+      if (params.uncoveredRoads === 'sim' || params.uncoveredRoads === 'hide') {
+        layerState._uncoveredMode = params.uncoveredRoads;
+      }
+      // Jam-viz prototype toggle (owner A/B): 'none' = shipped main behavior;
+      // live mode only, applies on the next camera-driven load like the
+      // uncoveredRoads param above.
+      if (['none', 'density', 'heatline', 'both'].includes(params.jamViz)) {
+        layerState._jamViz = params.jamViz;
+      }
+      // Preset-aware dot styling kill switch (owner A/B): 'off' forces the
+      // shipped palette under every post-FX preset. Applies immediately via
+      // in-place restyle — no refetch — so A/B legs share identical dots.
+      if (params.presetDots === 'on' || params.presetDots === 'off') {
+        if (params.presetDots !== layerState._presetDots) {
+          layerState._presetDots = params.presetDots;
+          parts.style.restyleDotsInPlace();
+        }
+      }
+    },
+
+    /**
+     * Return the current user-adjustable parameters.
+     * @returns {{densityScale:number, speedScale:number}}
+     */
+    getParams() {
+      return {
+        densityScale: layerState._densityScale,
+        speedScale: layerState._speedScale,
+        uncoveredRoads: layerState._uncoveredMode,
+        jamViz: layerState._jamViz,
+        presetDots: layerState._presetDots,
+      };
+    },
+
+    /**
+     * Return a sub-sampled list of active dot positions for detection overlays
+     * (e.g. CCTV bounding-box rendering).
+     *
+     * Uses a deterministic stride-based sampling so different seeds yield
+     * non-overlapping subsets without sorting or shuffling.
+     *
+     * @param {Object}  [options]
+     * @param {number}  [options.maxCount] - Maximum objects to return (defaults to all).
+     * @param {number}  [options.seed]     - Integer seed to offset the sampling start.
+     * @returns {Array<{position:Cesium.Cartesian3, id:string, type:string}>}
+     */
+    getDetectableObjects(options = {}) {
+      if (!layerState._enabled || layerState._dots.length === 0) return [];
+      const maxCount = Number.isFinite(options.maxCount)
+        ? Math.max(1, Math.floor(options.maxCount))
+        : layerState._dots.length;
+      const seed = Number.isFinite(options.seed) ? Math.floor(options.seed) : 0;
+      // Stride-based sampling: step through dots evenly to get ~maxCount samples
+      const stride = Math.max(1, Math.ceil(layerState._dots.length / maxCount));
+      const start = seed % stride;
+
+      const result = [];
+      for (let i = start; i < layerState._dots.length; i += stride) {
+        const pos = layerState._dots[i].point.position;
+        if (!pos) continue;
+        const entry = {
+          position: pos,
+          id: `VEH-${String(i).padStart(4, '0')}`,
+          type: 'VEH',
+        };
+        // Live mode: the detection bracket carries the congestion signal —
+        // its canvas sits ABOVE the post-FX chain, so tier colors survive
+        // every preset (owner round 2: "bounding boxes do the heavy
+        // lifting"). Keyless mode sets no tier: contacts keep the stock
+        // 'vehicle' bracket and the keyless experience stays untouched.
+        if (layerState._liveMode) {
+          const tier = trafficBucketTier(layerState._dots[i].bucket || 'sim');
+          if (tier) entry.tier = tier;
+        }
+        result.push(entry);
+        if (result.length >= maxCount) break;
+      }
+      return result;
+    },
+
+    /**
+     * Return current layer statistics for UI status chips.
+     * `mode` is the CONFIGURED source — 'live' (a TomTom key is present) or
+     * 'sim' (keyless simulation, which the manager renders as a FALLBACK chip);
+     * `error` carries this instant's health, so a live-configured layer whose
+     * flow feed went down reads DEGRADED with the reason instead of a stale
+     * LIVE coverage number. `flowCoveragePct` is matched roads / roads with any
+     * flow candidates (0–100 int); `tilesFetched` counts flow-tile requests
+     * issued to the proxy this session (decode-cache hits excluded).
+     * @returns {{count:number, lastUpdate:number|null, loading:boolean,
+     *   mode:'live'|'sim', error:string|null, flowCoveragePct:number,
+     *   tilesFetched:number}}
+     */
+    getStats() {
+      // Outstanding flow work counts as loading: the paint race can leave a
+      // TomTom request in flight after the roads have settled, and the shared
+      // loading batch has to stay open long enough to announce its failure.
+      const loading = layerState._fetching || layerState._flowPending > 0;
+      const feed = parts.model.trafficFeedPresentation({
+        liveMode: layerState._liveMode,
+        fetching: loading,
+        flowError: layerState._flowError,
+        coveragePct: layerState._flowCoveragePct,
+        statusUnavailable: layerState._flowStatusUnavailable,
+      });
+      return {
+        count: layerState._count,
+        lastUpdate: layerState._lastUpdate,
+        loading,
+        mode: feed.mode,
+        error: feed.error,
+        flowCoveragePct: layerState._flowCoveragePct,
+        tilesFetched: getFlowSessionStats().tilesFetched,
+        ...(TRAFFIC_TIMING_ENABLED
+          ? { trafficTiming: parts.timing.getTrafficTimingDiagnostics() }
+          : {}),
+        // Per-bucket rendered-dot counts (sim = white ambient). Drives the
+        // qa-traffic color assertions and the sync-chip mode label below.
+        flowBuckets: { ...layerState._bucketCounts },
+        closedRoads: layerState._closedRoads,
+        // Jam-viz prototype diagnostics (additive — harness contract untouched).
+        heatLines: layerState._heatLineCount,
+        jamViz: layerState._jamViz,
+        // Preset-styling diagnostics (additive): active style + profile.
+        stylePreset: layerState._stylePreset,
+        styleProfile:
+          layerState._presetDots === 'on'
+            ? trafficStyleProfile(layerState._stylePreset)
+            : 'normal',
+        // Sync-chip text: shown while busy, and flashed on its own for 1.5 s
+        // after each completed load (ui.js _updateTrafficSyncChip semantics).
+        // The settled flash carries NO progress number beside it — this label's
+        // coverage figure is the chip's only percentage — so a label that ends
+        // in one had better be the honest one. This is also where LIVE vs
+        // SIMULATED mode is surfaced, and it must never imply a live feed the
+        // layer does not have.
+        loadingLabel: feed.loadingLabel,
+      };
+    },
+  };
+
+  return { methods };
+}

src/layers/traffic/flow.js

@@ -0,0 +1,214 @@
+import { matchFlowToRoads } from '../../data/flowMatch.js';
+import { TRAFFIC_TIMING_ENABLED, FLOW_RENDER_RACE_MS } from './policy.js';
+
+export function createFlow({ state: layerState, services, parts, source }) {
+  const { registerDynamicCredit, TOMTOM_CREDIT } = services.credits;
+  const { fetchFlowForBounds } = source;
+
+  // ─── Live Flow (TomTom) ────────────────────────────────────
+
+  /**
+   * Map a failed flow fetch onto one short, honest user-facing reason.
+   *
+   * `fetchFlowForBounds` only rejects when EVERY covering tile failed, so a
+   * non-null result here always means "there is no live flow to show right
+   * now" — the dots fall back to simulated white. Mirrors the
+   * `deriveAisFeedError` honesty helper.
+   *
+   * @param {Error|{name?:string, message?:string}|null|undefined} error - Rejection from the flow fetch.
+   * @returns {string|null} Short reason, or null for an aborted (superseded) fetch.
+   */
+
+  function deriveTrafficFlowError(error) {
+    if (!error || error.name === 'AbortError') return null;
+    const message = String(error.message || error);
+    const status = Number(message.match(/HTTP (\d{3})/)?.[1]);
+    if (status === 503) return 'TomTom key unavailable';
+    if (status === 429) return 'TomTom daily budget reached';
+    if (status === 502 || status === 504) return 'TomTom upstream unreachable';
+    if (Number.isFinite(status)) return `TomTom flow error (HTTP ${status})`;
+    return 'TomTom flow unavailable';
+  }
+
+  /**
+   * Check `/api/tomtom/status` once per session and cache the result.
+   * Live mode iff the server holds a TomTom key; the TomTom attribution credit
+   * registers the first time live mode activates. Keyless or unreachable →
+   * simulation mode, exactly today's behavior.
+   *
+   * @returns {Promise<void>} Resolves when `_liveMode` is settled.
+   */
+
+  function ensureFlowStatus() {
+    if (!layerState._flowStatusPromise) {
+      layerState._flowStatusPromise = source
+        .getStatus()
+        .then((status) => {
+          layerState._liveMode = Boolean(status?.hasKey);
+          layerState._flowStatusUnavailable = false;
+          if (layerState._liveMode) {
+            console.log('[Data:Traffic] TomTom key present — live flow mode');
+            registerDynamicCredit(layerState._viewer, TOMTOM_CREDIT);
+          }
+        })
+        .catch((e) => {
+          // Simulating because we could not ask, which is NOT the same as
+          // "server says no key" — getStats() distinguishes the two.
+          layerState._liveMode = false;
+          layerState._flowStatusUnavailable = true;
+          console.warn(
+            '[Data:Traffic] TomTom status unreachable — simulated traffic:',
+            e?.message || e,
+          );
+        });
+    }
+    return layerState._flowStatusPromise;
+  }
+
+  /**
+   * Live mode only: fetch TomTom flow for the clamped bounds, match it onto the
+   * parsed roads, and attach `road.flow` (`{level, closure}` or null).
+   *
+   * Reuses the load-generation guard: stale flow responses are discarded, and
+   * the shared AbortController lets `cancelActiveFetch()` (next load / disable)
+   * cancel an in-flight flow fetch. Any failure leaves roads unmatched — the
+   * dots then render in today's simulated white, never a phantom color — and is
+   * recorded in `_flowError` so `getStats()` degrades honestly instead of
+   * reporting a stale "LIVE · N% cov" over simulated dots.
+   *
+   * @param {Array} roads - Parsed road objects (mutated: `road.flow`).
+   * @param {{south:number,west:number,north:number,east:number}} clamped - Fetch bounds.
+   * @param {number} generation - `_loadGeneration` at call time.
+   * @returns {Promise<void>}
+   */
+
+  async function applyFlowToRoads(roads, clamped, generation) {
+    // Claim the work synchronously, before the first await, so `stats.loading`
+    // covers this request from the same tick the caller started it — the
+    // loading batch must not be able to close underneath an in-flight fetch.
+    layerState._flowPending += 1;
+    try {
+      if (!layerState._flowStatusPromise) return; // status check not started — sim mode
+      await layerState._flowStatusPromise;
+      if (!layerState._liveMode || !layerState._enabled) return;
+      if (generation !== layerState._loadGeneration) return;
+      if (!Array.isArray(roads) || roads.length === 0) return;
+      try {
+        // Cached paths reach here without a live controller; the fetch paths
+        // reuse theirs so one cancel covers both roads and flow.
+        if (!layerState._activeFetchAbort)
+          layerState._activeFetchAbort = new AbortController();
+        const segments = await fetchFlowForBounds(clamped, {
+          signal: layerState._activeFetchAbort.signal,
+        });
+        if (generation !== layerState._loadGeneration) return;
+        const { matches, matchedCount, candidateCount } = matchFlowToRoads(
+          roads,
+          segments,
+        );
+        for (let i = 0; i < roads.length; i++) {
+          roads[i].flow = matches[i];
+        }
+        layerState._flowCoveragePct =
+          candidateCount > 0
+            ? Math.round((matchedCount / candidateCount) * 100)
+            : 0;
+        layerState._flowError = null;
+      } catch (e) {
+        if (e?.name === 'AbortError') return;
+        // Same guard the success path gets: a superseded request rejecting late
+        // (or after disable() cleared the state) must not restore a stale
+        // outage over newer good data.
+        if (generation !== layerState._loadGeneration || !layerState._enabled)
+          return;
+        // Every covering tile failed: there is no live flow on screen. Drop the
+        // now-false coverage number and surface the reason through getStats().
+        layerState._flowError = deriveTrafficFlowError(e);
+        layerState._flowCoveragePct = 0;
+        console.warn(
+          '[Data:Traffic] Flow fetch failed (sim colors remain):',
+          e?.message || e,
+        );
+      }
+    } finally {
+      layerState._flowPending -= 1;
+    }
+  }
+
+  /**
+   * Race flow application against the paint deadline, render, and schedule an
+   * in-place recolor if flow lost the race.
+   * @param {Array} roads - Parsed road objects.
+   * @param {{south:number,west:number,north:number,east:number}} clamped - Fetch bounds.
+   * @param {number} generation - `_loadGeneration` at call time.
+   * @param {number} altitude - Camera altitude in meters.
+   * @param {string} label - Render log label.
+   * @param {Object|null} [trace=null] - Development-only correlated load trace.
+   * @returns {Promise<boolean>} True if this generation rendered.
+   */
+
+  async function applyFlowThenRender(
+    roads,
+    clamped,
+    generation,
+    altitude,
+    label,
+    trace = null,
+  ) {
+    const state =
+      TRAFFIC_TIMING_ENABLED && trace
+        ? parts.timing.trafficTimingRenderState(trace, label)
+        : null;
+    const flowRaceStart = state
+      ? parts.timing.trafficTimingMark(state, 'flow-render-race-start', {
+          deadlineMs: FLOW_RENDER_RACE_MS,
+        })
+      : null;
+    const flowJob = applyFlowToRoads(roads, clamped, generation);
+    const outcome = await Promise.race([
+      flowJob.then(() => 'flow'),
+      new Promise((resolve) =>
+        setTimeout(() => resolve('timeout'), FLOW_RENDER_RACE_MS),
+      ),
+    ]);
+    if (state) {
+      const flowRaceEnd = parts.timing.trafficTimingMark(
+        state,
+        'flow-render-race-end',
+        {
+          deadlineMs: FLOW_RENDER_RACE_MS,
+          outcome,
+        },
+      );
+      parts.timing.trafficTimingMeasure(
+        'flow-render-race',
+        state,
+        flowRaceStart,
+        flowRaceEnd,
+        {
+          deadlineMs: FLOW_RENDER_RACE_MS,
+          outcome,
+        },
+      );
+    }
+    if (generation !== layerState._loadGeneration) return false;
+    parts.rendering.renderRoadsForAltitude(roads, altitude, label, trace);
+    if (outcome === 'timeout') {
+      flowJob
+        .then(() => {
+          if (generation !== layerState._loadGeneration) return;
+          parts.model.recolorDotsInPlace(label);
+        })
+        .catch(() => {
+          /* applyFlowToRoads settles its own failures */
+        });
+    }
+    return true;
+  }
+  return {
+    deriveTrafficFlowError,
+    ensureFlowStatus,
+    applyFlowToRoads,
+    applyFlowThenRender,
+  };
+}

src/layers/traffic/flowDecode.js

@@ -0,0 +1,70 @@
+import { PbfReader } from 'pbf';
+import { VectorTile } from '@mapbox/vector-tile';
+
+/**
+ * @file TomTom traffic-flow vector-tile client: fetch + MVT decode.
+ *
+ * Fetches flow tiles from the local `/api/tomtom/flow/{z}/{x}/{y}.pbf` proxy
+ * (the TomTom key never reaches the browser) and decodes the Mapbox Vector
+ * Tile layer "Traffic flow" into plain lon/lat polylines with congestion
+ * attributes. Consumed by the traffic layer's live mode
+ * (`src/data/traffic.js` → `src/data/flowMatch.js`).
+ *
+ * Segment shape: `{coords: [[lon,lat],…], trafficLevel: 0..1, roadType: string,
+ * closure: boolean}` — `trafficLevel` is TomTom's current/free-flow speed
+ * ratio (1 = free flow). Features with a missing/non-finite `traffic_level`
+ * are skipped unless `road_closure` is true (closures decode with level 0).
+ *
+ * Deps: `pbf@5` (PbfReader) + `@mapbox/vector-tile@3` — both tiny and
+ * tree-shakeable; decoding happens client-side so the proxy stays a dumb
+ * binary cache.
+ *
+ * @module data/flowTiles
+ */
+
+const FLOW_LAYER_NAME = 'Traffic flow';
+export function decodeFlowTile(data, z, x, y) {
+  let layer;
+  try {
+    const bytes = data instanceof ArrayBuffer ? new Uint8Array(data) : data;
+    const tile = new VectorTile(new PbfReader(bytes));
+    layer = tile.layers[FLOW_LAYER_NAME];
+  } catch {
+    return [];
+  }
+  if (!layer) return [];
+
+  const segments = [];
+  for (let i = 0; i < layer.length; i++) {
+    let feature;
+    let geometry;
+    try {
+      feature = layer.feature(i);
+      geometry = feature.toGeoJSON(x, y, z).geometry;
+    } catch {
+      continue; // one malformed feature must not drop the tile
+    }
+    const props = feature.properties || {};
+    const closure =
+      props.road_closure === true || props.road_closure === 'true';
+    const rawLevel = props.traffic_level;
+    const hasLevel = typeof rawLevel === 'number' && Number.isFinite(rawLevel);
+    // Skip features we can't color — unless closed (closures render dot-free
+    // regardless of level, so they stay useful without one).
+    if (!hasLevel && !closure) continue;
+    const trafficLevel = hasLevel ? Math.min(1, Math.max(0, rawLevel)) : 0;
+    const roadType = typeof props.road_type === 'string' ? props.road_type : '';
+
+    const lines =
+      geometry.type === 'LineString'
+        ? [geometry.coordinates]
+        : geometry.type === 'MultiLineString'
+          ? geometry.coordinates
+          : [];
+    for (const coords of lines) {
+      if (!Array.isArray(coords) || coords.length < 2) continue;
+      segments.push({ coords, trafficLevel, roadType, closure });
+    }
+  }
+  return segments;
+}

src/layers/traffic/flowSource.js

@@ -0,0 +1,97 @@
+import { tilesForBounds } from '../../data/tomtomTiles.js';
+import { decodeFlowTile } from './flowDecode.js';
+/** Own one decoded flow cache and its session counters. */
+export function createFlowTileSource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+} = {}) {
+  const DECODE_CACHE_TTL_MS = 120_000;
+  /** @const {number} Max decoded tiles kept in memory before oldest-entry eviction. */
+  const DECODE_CACHE_MAX_ENTRIES = 64;
+
+  /**
+   * Decoded-tile cache keyed by "z/x/y".
+   * @type {Map<string, {at:number, segments:Array}>}
+   */
+  const _decodeCache = new Map();
+  /** @type {number} Session count of tile requests issued to the proxy (decode-cache misses). */
+  let _tilesFetched = 0;
+
+  /** Insert into the decode cache with oldest-entry eviction. */
+  function cacheSet(key, entry) {
+    if (
+      !_decodeCache.has(key) &&
+      _decodeCache.size >= DECODE_CACHE_MAX_ENTRIES
+    ) {
+      const oldest = _decodeCache.keys().next().value;
+      _decodeCache.delete(oldest);
+    }
+    _decodeCache.set(key, entry);
+  }
+
+  /**
+   * Fetch + decode all flow tiles covering the given bounds.
+   *
+   * Tiles are fetched from the local proxy in parallel; each decoded tile is
+   * cached in memory for 120 s (keyed z/x/y), so repeat calls for the same
+   * viewport are free. Partial tile failures return the segments that DID
+   * decode (last-good philosophy); the promise rejects only when every tile
+   * failed (e.g. keyless 503, aborted signal, proxy down).
+   *
+   * @param {{south:number, west:number, north:number, east:number}} bounds - Degrees.
+   * @param {Object} [opts]
+   * @param {AbortSignal} [opts.signal] - Abort signal (camera moved / layer disabled).
+   * @param {number} [opts.zoom=12] - Flow tile zoom level.
+   * @returns {Promise<Array<{coords:number[][], trafficLevel:number, roadType:string, closure:boolean}>>}
+   *   Flat array of flow segments across all covering tiles.
+   */
+  async function fetchFlowForBounds(bounds, { signal, zoom = 12 } = {}) {
+    signal?.throwIfAborted();
+    const tiles = tilesForBounds(bounds, zoom);
+    if (tiles.length === 0) return [];
+    const now = Date.now();
+
+    const results = await Promise.allSettled(
+      tiles.map(async ({ z, x, y }) => {
+        const key = `${z}/${x}/${y}`;
+        const cached = _decodeCache.get(key);
+        if (cached && now - cached.at < DECODE_CACHE_TTL_MS)
+          return cached.segments;
+
+        _tilesFetched += 1;
+        const res = await fetchImpl(`/api/tomtom/flow/${z}/${x}/${y}.pbf`, {
+          signal,
+        });
+        if (!res.ok) throw new Error(`flow tile ${key}: HTTP ${res.status}`);
+        const segments = decodeFlowTile(await res.arrayBuffer(), z, x, y);
+        signal?.throwIfAborted();
+        cacheSet(key, { at: Date.now(), segments });
+        return segments;
+      }),
+    );
+
+    signal?.throwIfAborted();
+    const fulfilled = results.filter((r) => r.status === 'fulfilled');
+    if (fulfilled.length === 0) {
+      throw results[0].reason instanceof Error
+        ? results[0].reason
+        : new Error('flow fetch failed');
+    }
+    return fulfilled.flatMap((r) => r.value);
+  }
+
+  /**
+   * Session diagnostics for `getStats()` surfaces.
+   * @returns {{tilesFetched:number}} Count of tile requests issued to the proxy
+   *   this session (decode-cache hits excluded).
+   */
+  function getFlowSessionStats() {
+    return { tilesFetched: _tilesFetched };
+  }
+
+  /** Clear the decode cache (tests + layer teardown). Session stats persist. */
+  function resetFlowTileCache() {
+    _decodeCache.clear();
+  }
+
+  return { fetchFlowForBounds, getFlowSessionStats, resetFlowTileCache };
+}

src/layers/traffic/index.js

@@ -0,0 +1,63 @@
+import { TRAFFIC_TIMING_ENABLED } from './policy.js';
+import { createStyle } from './style.js';
+import { createTiming } from './timing.js';
+import { createModel } from './model.js';
+import { createIngestion } from './ingestion.js';
+import { createAnimation } from './animation.js';
+import { createViewport } from './viewport.js';
+import { createFlow } from './flow.js';
+import { createRendering } from './rendering.js';
+import { createControls } from './controls.js';
+import { createLifecycle } from './lifecycle.js';
+import { createState } from './state.js';
+
+/** Construct one layer with its own scene state and supplied application services. */
+export function createTrafficLayer({ services, source }) {
+  if (
+    ![
+      'requestRoads',
+      'getStatus',
+      'fetchFlowForBounds',
+      'getFlowSessionStats',
+      'resetFlowTileCache',
+    ].every((key) => typeof source?.[key] === 'function')
+  )
+    throw new TypeError('A traffic source is required');
+  const state = createState({ services });
+  const parts = {};
+  const context = { state, services, parts, source };
+  parts.style = createStyle(context);
+  parts.timing = createTiming(context);
+  parts.model = createModel(context);
+  parts.ingestion = createIngestion(context);
+  parts.animation = createAnimation(context);
+  parts.viewport = createViewport(context);
+  parts.flow = createFlow(context);
+  parts.rendering = createRendering(context);
+  parts.controls = createControls(context);
+  parts.lifecycle = createLifecycle(context);
+  state._parseRoads = TRAFFIC_TIMING_ENABLED
+    ? (data, trace) =>
+        trace
+          ? parts.timing.parseRoadsTimed(data, trace)
+          : parts.model.parseRoads(data)
+    : parts.model.parseRoads;
+
+  state._loadRoadsForBounds = TRAFFIC_TIMING_ENABLED
+    ? parts.timing.loadRoadsForBoundsTimed
+    : parts.ingestion.loadRoadsForBounds;
+
+  return Object.assign(
+    {},
+    parts.controls.methods,
+    parts.lifecycle.methods,
+    parts.ingestion?.methods,
+    {
+      getTrafficTimingDiagnostics: parts.timing.getTrafficTimingDiagnostics,
+      deriveTrafficFlowError: parts.flow.deriveTrafficFlowError,
+      trafficFeedPresentation: parts.model.trafficFeedPresentation,
+    },
+  );
+}
+
+export { createTrafficSource } from './source.js';

src/layers/traffic/ingestion.js

@@ -0,0 +1,329 @@
+import {
+  TRAFFIC_TIMING_ENABLED,
+  OVERPASS_URL,
+  TILE_CACHE_MAX_ENTRIES,
+  FAST_FETCH_ALTITUDE,
+} from './policy.js';
+
+export function createIngestion({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  const { fetchFlowForBounds } = source;
+
+  /**
+   * Fetch road geometries from the Overpass API via the local proxy.
+   *
+   * Sends a POST with the query as form-encoded `data`. Supports
+   * AbortController signals so in-flight requests can be cancelled
+   * when the camera moves before the response arrives.
+   *
+   * @param {number} south - Southern latitude bound (degrees).
+   * @param {number} west  - Western longitude bound (degrees).
+   * @param {number} north - Northern latitude bound (degrees).
+   * @param {number} east  - Eastern longitude bound (degrees).
+   * @param {Object}  [opts]
+   * @param {boolean} [opts.majorOnly=false]  - Restrict to major highway classes.
+   * @param {number}  [opts.timeoutSec=25]    - Server-side Overpass timeout.
+   * @param {AbortSignal} [opts.signal]       - Abort signal for cancellation.
+   * @param {Object|null} [trace=null] - Development-only correlated load trace.
+   * @returns {Promise<Object>} Parsed JSON response from Overpass.
+   * @throws {Error} If the HTTP response status is not OK.
+   */
+
+  async function fetchRoads(
+    south,
+    west,
+    north,
+    east,
+    { majorOnly = false, timeoutSec = 25, signal } = {},
+    trace = null,
+  ) {
+    const state =
+      TRAFFIC_TIMING_ENABLED && trace
+        ? parts.timing.trafficTimingPass(
+            trace,
+            majorOnly ? 'major' : 'full',
+            'proxy',
+          )
+        : null;
+    if (state) trace.currentPass = state.pass;
+    const fetchStart = state
+      ? parts.timing.trafficTimingMark(state, 'fetch-start')
+      : null;
+    if (state) {
+      parts.timing.trafficTimingMeasure(
+        'last-camera-change-to-fetch-start',
+        state,
+        trace.cameraChangeMark,
+        fetchStart,
+      );
+    }
+    const response = await source.requestRoads(
+      { south, west, north, east },
+      { majorOnly, timeoutSec, signal },
+    );
+
+    if (!response.ok) {
+      throw new Error(`Overpass API returned ${response.status}`);
+    }
+
+    if (!state) {
+      const data = await response.json();
+      signal?.throwIfAborted();
+      if (!Array.isArray(data?.elements))
+        throw new Error('Malformed road snapshot');
+      return data;
+    }
+
+    if (state) {
+      state.proxyCache = response.headers.get('x-overpass-cache');
+      state.proxyUpstream = response.headers.get('x-overpass-upstream');
+    }
+    const responseStart = state
+      ? parts.timing.trafficTimingMark(state, 'response-json-start', {
+          responseStatus: response.status,
+        })
+      : null;
+    if (state) {
+      parts.timing.trafficTimingMeasure(
+        'fetch-to-response',
+        state,
+        fetchStart,
+        responseStart,
+        {
+          responseStatus: response.status,
+        },
+      );
+    }
+    const data = await response.json();
+    signal?.throwIfAborted();
+    if (!Array.isArray(data?.elements))
+      throw new Error('Malformed road snapshot');
+    if (state) {
+      const responseEnd = parts.timing.trafficTimingMark(
+        state,
+        'response-json-end',
+        {
+          responseStatus: response.status,
+        },
+      );
+      parts.timing.trafficTimingMeasure(
+        'response-json',
+        state,
+        responseStart,
+        responseEnd,
+        {
+          responseStatus: response.status,
+        },
+      );
+    }
+    return data;
+  }
+
+  /** Abort any in-flight Overpass fetch and clear the controller reference. */
+
+  function cancelActiveFetch() {
+    if (layerState._activeFetchAbort) {
+      layerState._activeFetchAbort.abort();
+      layerState._activeFetchAbort = null;
+    }
+  }
+
+  /**
+   * Load road data for the given viewport bounds and render traffic dots.
+   *
+   * Implements a two-pass fetch strategy with tile caching:
+   *
+   *  1. Check the tile cache (keyed by clamped bounding-box coordinates).
+   *     - If a full road set is cached, render immediately and return.
+   *     - If only major roads are cached, render those first.
+   *  2. Fetch major roads from Overpass (fast, small payload). Render.
+   *  3. If altitude is low enough (< FAST_FETCH_ALTITUDE), fetch the full
+   *     road graph (includes tertiary/residential). Render again to upgrade.
+   *
+   * Each fetch is guarded by a monotonic `_loadGeneration` counter so that
+   * stale responses from superseded requests are silently discarded.
+   *
+   * @param {{south:number, west:number, north:number, east:number}} bounds
+   *   Viewport bounds (will be clamped internally).
+   * @param {number} altitude - Camera altitude in meters.
+   * @param {Object|null} [trace=null] - Development-only correlated load trace.
+   * @returns {Promise<void>}
+   */
+
+  async function loadRoadsForBounds(bounds, altitude, trace = null) {
+    // Increment generation to invalidate any in-flight responses from prior calls
+    const generation = ++layerState._loadGeneration;
+    cancelActiveFetch();
+    const clamped = parts.viewport.clampBounds(bounds);
+
+    // Cache key: fixed-precision bounding-box string for deterministic lookups
+    const cacheKey = `${clamped.south.toFixed(4)},${clamped.west.toFixed(4)},${clamped.north.toFixed(4)},${clamped.east.toFixed(4)}`;
+
+    // Live mode: warm the flow-tile cache CONCURRENTLY with the Overpass road
+    // fetch — sequential fetches doubled first-paint latency (field-test
+    // round 1). Failures are irrelevant; applyFlowToRoads settles the truth.
+    parts.flow.ensureFlowStatus().then(() => {
+      if (
+        layerState._liveMode &&
+        layerState._enabled &&
+        generation === layerState._loadGeneration
+      ) {
+        fetchFlowForBounds(clamped, {}).catch(() => {
+          /* warm-up only */
+        });
+      }
+    });
+
+    layerState._fetching = true;
+    // Only COMMIT these on success. Committing up-front means a failed Overpass
+    // fetch (rate-limited / feed down) still trips the overlap gate in
+    // onCameraChanged, so a stationary user never retries (H3/H5). Stage the
+    // prospective values and roll back if nothing rendered.
+    const prevBounds = layerState._lastBounds;
+    const prevViewCenter = layerState._lastViewCenter;
+    layerState._lastBounds = clamped;
+    layerState._lastViewCenter = parts.viewport.getBoundsCenter(clamped);
+    let renderedSomething = false;
+
+    try {
+      let cache = layerState._tileCache.get(cacheKey);
+      if (!cache) {
+        // LRU eviction: drop the oldest entry when cache exceeds the cap
+        if (layerState._tileCache.size >= TILE_CACHE_MAX_ENTRIES) {
+          const oldest = layerState._tileCache.keys().next().value;
+          layerState._tileCache.delete(oldest);
+        }
+        cache = { major: null, full: null };
+        layerState._tileCache.set(cacheKey, cache);
+      }
+
+      // Fast path: full road set already cached — render and return.
+      // Flow is (re)applied even on cache hits: roads cache for the session,
+      // but congestion data has a 120s shelf life. The race renders within
+      // FLOW_RENDER_RACE_MS either way; late flow recolors in place.
+      if (cache.full) {
+        renderedSomething = await parts.flow.applyFlowThenRender(
+          cache.full,
+          clamped,
+          generation,
+          altitude,
+          'Cache full',
+          trace,
+        );
+        return;
+      }
+
+      // Intermediate path: render cached major roads while fetching the rest
+      if (cache.major) {
+        if (
+          !(await parts.flow.applyFlowThenRender(
+            cache.major,
+            clamped,
+            generation,
+            altitude,
+            'Cache major',
+            trace,
+          ))
+        )
+          return;
+        renderedSomething = true;
+      } else {
+        // Fetch major roads first (smaller payload, faster response)
+        layerState._activeFetchAbort = new AbortController();
+        console.log(`[Data:Traffic] Fast fetch major roads [${cacheKey}]`);
+        const majorData = await fetchRoads(
+          clamped.south,
+          clamped.west,
+          clamped.north,
+          clamped.east,
+          {
+            majorOnly: true,
+            timeoutSec: 12,
+            signal: layerState._activeFetchAbort.signal,
+          },
+          trace,
+        );
+        // Discard stale response if a newer load was triggered while waiting
+        if (generation !== layerState._loadGeneration) return;
+        cache.major = layerState._parseRoads(majorData, trace);
+        if (
+          !(await parts.flow.applyFlowThenRender(
+            cache.major,
+            clamped,
+            generation,
+            altitude,
+            'Loaded major',
+            trace,
+          ))
+        )
+          return;
+        renderedSomething = true;
+      }
+
+      // At higher altitude, major roads provide sufficient motion density
+      if (altitude > FAST_FETCH_ALTITUDE) return;
+
+      // Detailed pass: fetch the full road graph (tertiary, residential, etc.)
+      layerState._activeFetchAbort = new AbortController();
+      console.log(`[Data:Traffic] Full fetch local roads [${cacheKey}]`);
+      const fullData = await fetchRoads(
+        clamped.south,
+        clamped.west,
+        clamped.north,
+        clamped.east,
+        {
+          majorOnly: false,
+          timeoutSec: 20,
+          signal: layerState._activeFetchAbort.signal,
+        },
+        trace,
+      );
+      if (generation !== layerState._loadGeneration) return;
+
+      cache.full = layerState._parseRoads(fullData, trace);
+      if (
+        !(await parts.flow.applyFlowThenRender(
+          cache.full,
+          clamped,
+          generation,
+          altitude,
+          'Loaded full',
+          trace,
+        ))
+      )
+        return;
+      renderedSomething = true;
+    } catch (e) {
+      if (e?.name === 'AbortError') return;
+      console.warn('[Data:Traffic] Fetch error:', e);
+    } finally {
+      if (generation === layerState._loadGeneration) {
+        layerState._fetching = false;
+        // Roll back the bounds commit if this load rendered nothing (e.g. the
+        // Overpass fetch failed). Leaving them committed would make the overlap
+        // gate skip the retry while the user sits still. Guarded on generation so
+        // a superseding load's commit is not clobbered.
+        if (!renderedSomething) {
+          layerState._lastBounds = prevBounds;
+          layerState._lastViewCenter = prevViewCenter;
+        }
+      }
+      layerState._activeFetchAbort = null;
+    }
+  }
+  const methods = {
+    /**
+     * No-op — traffic updates are entirely camera-driven, not timer-driven.
+     * @returns {Promise<void>}
+     */
+    async update() {
+      // No-op — updates are camera-driven
+    },
+  };
+
+  return { fetchRoads, cancelActiveFetch, loadRoadsForBounds, methods };
+}

src/layers/traffic/lifecycle.js

@@ -0,0 +1,188 @@
+import * as Cesium from 'cesium';
+import { TRAFFIC_TIMING_ENABLED } from './policy.js';
+
+export function createLifecycle({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  const { holdContinuousRender, releaseContinuousRender } = services.render;
+  const { resetFlowTileCache } = source;
+
+  const methods = {
+    /**
+     * One-time initialisation. Creates the PointPrimitiveCollection and adds it
+     * to the scene (hidden). The collection is never removed and re-added — only
+     * toggled via `.show` to avoid destroy-on-remove errors.
+     *
+     * @param {Cesium.Viewer} viewer - The Cesium viewer instance.
+     */
+    init(viewer) {
+      layerState._viewer = viewer;
+      layerState._pointCollection = new Cesium.PointPrimitiveCollection({
+        blendOption: Cesium.BlendOption.TRANSLUCENT,
+      });
+      // Add permanently — toggle with .show to avoid destroy-on-remove errors
+      viewer.scene.primitives.add(layerState._pointCollection);
+      layerState._pointCollection.show = false;
+      layerState._dots = [];
+      layerState._roads = [];
+      layerState._count = 0;
+      layerState._lastUpdate = null;
+      layerState._lastBounds = null;
+      layerState._fetching = false;
+      layerState._loadGeneration = 0;
+      layerState._densityScale = 1.0;
+      layerState._speedScale = 1.0;
+      layerState._lastViewCenter = null;
+      layerState._flowCoveragePct = 0;
+      layerState._flowError = null;
+      if (TRAFFIC_TIMING_ENABLED) {
+        layerState._trafficTimingCurrentAnchor = null;
+        layerState._trafficTimingSequence = 0;
+        layerState._trafficTimingTracesCreated = 0;
+        layerState._trafficTimingDroppedTraces = 0;
+      }
+
+      // Preset-aware dot styling: adopt the active post-FX style (persisted
+      // style restore may run before layer registration, so read the dataset)
+      // and follow StyleManager's gev:style-change event thereafter. Guarded
+      // for non-browser contexts; bound once per page (init survives layer
+      // destroy/re-register).
+      if (typeof window !== 'undefined') {
+        layerState._stylePreset =
+          document?.documentElement?.dataset?.gevStyle || 'normal';
+        if (!layerState._styleListenerBound) {
+          window.addEventListener('gev:style-change', (e) =>
+            parts.style.setStylePreset(e?.detail?.style),
+          );
+          layerState._styleListenerBound = true;
+        }
+      }
+      parts.style.refreshBucketColors();
+      console.log('[Data:Traffic] Initialized');
+    },
+
+    /**
+     * Enable the traffic layer. Shows the point collection, subscribes to the
+     * preRender animation loop and camera-change events, and kicks off an
+     * initial viewport check.
+     *
+     * @param {Cesium.Viewer} viewer - The Cesium viewer instance.
+     */
+    enable(viewer) {
+      layerState._enabled = true;
+      holdContinuousRender('traffic'); // per-frame animator (perf wave 2)
+      layerState._lastAnimTime = 0;
+      layerState._pointCollection.show = true;
+
+      // One status check per session decides sim vs live-TomTom mode.
+      parts.flow.ensureFlowStatus();
+
+      layerState._preRenderRemover = viewer.scene.preRender.addEventListener(
+        parts.animation.animate,
+      );
+      if (TRAFFIC_TIMING_ENABLED) {
+        parts.timing.clearTrafficTimingEntries();
+        layerState._trafficTimingCurrentAnchor = null;
+        layerState._trafficTimingPostRenderRemovers = new Set();
+        layerState._trafficTimingMoveEndRemover =
+          viewer.camera.moveEnd.addEventListener(
+            parts.timing.markTrafficTimingMoveEnd,
+          );
+      }
+
+      // Subscribe to camera changes with a 5% movement threshold. Save the prior
+      // value so disable() can restore it — percentageChanged is a shared global
+      // on the camera and leaving it mutated affects every other camera.changed
+      // listener in the app.
+      viewer.camera.changed.addEventListener(parts.viewport.onCameraChanged);
+      layerState._prevPercentageChanged = viewer.camera.percentageChanged;
+      viewer.camera.percentageChanged = 0.05;
+
+      // Kick off initial viewport check
+      parts.viewport.onCameraChanged();
+
+      // Boot-order guard (field-test round 1: layer sat empty until the user
+      // moved): when the persisted layer state re-enables traffic during the
+      // intro flyTo, the initial check bails at high altitude — and a camera
+      // that then parks never re-fires camera.changed. Retry cheaply until the
+      // first load commits, then self-clear. Also acts as a safety kick if a
+      // failed first fetch left the viewport unloaded while parked.
+      clearInterval(layerState._enableKickTimer);
+      layerState._enableKickTimer = setInterval(() => {
+        if (!layerState._enabled || layerState._lastUpdate) {
+          clearInterval(layerState._enableKickTimer);
+          layerState._enableKickTimer = null;
+          return;
+        }
+        if (!layerState._fetching) parts.viewport.onCameraChanged();
+      }, 1500);
+    },
+
+    /**
+     * Disable the traffic layer. Cancels pending fetches, clears all dots,
+     * unsubscribes from events, and hides the point collection.
+     *
+     * @param {Cesium.Viewer} viewer - The Cesium viewer instance.
+     */
+    disable(viewer) {
+      layerState._enabled = false;
+      releaseContinuousRender('traffic');
+      clearTimeout(layerState._fetchTimeout);
+      clearInterval(layerState._enableKickTimer);
+      layerState._enableKickTimer = null;
+      parts.ingestion.cancelActiveFetch();
+      layerState._loadGeneration++;
+      parts.animation.clearDots();
+      layerState._lastViewCenter = null;
+      // A stale outage from the last session would misreport a fresh enable —
+      // the next load re-derives feed health from real evidence.
+      layerState._flowError = null;
+
+      if (layerState._preRenderRemover) {
+        layerState._preRenderRemover();
+        layerState._preRenderRemover = null;
+      }
+      if (TRAFFIC_TIMING_ENABLED) {
+        layerState._trafficTimingMoveEndRemover?.();
+        layerState._trafficTimingMoveEndRemover = null;
+        for (const remove of layerState._trafficTimingPostRenderRemovers || [])
+          remove();
+        layerState._trafficTimingPostRenderRemovers = null;
+        layerState._trafficTimingCurrentAnchor = null;
+      }
+
+      viewer.camera.changed.removeEventListener(parts.viewport.onCameraChanged);
+      // Restore the camera's global percentageChanged so other layers/listeners
+      // keep their expected sensitivity.
+      if (layerState._prevPercentageChanged != null) {
+        viewer.camera.percentageChanged = layerState._prevPercentageChanged;
+        layerState._prevPercentageChanged = null;
+      }
+      if (layerState._pointCollection) layerState._pointCollection.show = false;
+    },
+
+    /**
+     * Permanently tear down the layer. Disables it, removes the point collection
+     * from the scene, and clears the tile cache.
+     *
+     * @param {Cesium.Viewer} viewer - The Cesium viewer instance.
+     */
+    destroy(viewer) {
+      this.disable(viewer);
+      if (layerState._pointCollection) {
+        viewer.scene.primitives.remove(layerState._pointCollection);
+        layerState._pointCollection = null;
+      }
+      parts.rendering.removeHeatLines();
+      layerState._tileCache.clear();
+      resetFlowTileCache();
+      layerState._count = 0;
+      layerState._lastUpdate = null;
+    },
+  };
+
+  return { methods };
+}

src/layers/traffic/model.js

@@ -0,0 +1,417 @@
+import * as Cesium from 'cesium';
+import {
+  flowDensityMult,
+  flowBucket,
+  flowSpeedScale,
+} from '../../data/trafficFlowStyle.js';
+import {
+  MAX_WAYPOINTS_PER_ROAD,
+  DOT_HEIGHT_OFFSET,
+  DENSITY_MULT,
+  JAM_DOT_FAR_SCALE,
+  JAM_DOT_DEPTH_PUNCH,
+} from './policy.js';
+
+export function createModel({ state: layerState, services, parts, source }) {
+  // ─── Overpass API ──────────────────────────────────────────
+
+  /**
+   * Build an Overpass QL query string to fetch road ways within a bounding box.
+   *
+   * The query uses a highway tag regex filter. When `majorOnly` is true, only
+   * motorway/trunk/primary/secondary are included; otherwise all drivable road
+   * classes are fetched. The `out geom qt;` suffix returns inline geometry
+   * (lat/lon per node) sorted by quadtile for faster server response.
+   *
+   * @param {number} south - Southern latitude bound (degrees).
+   * @param {number} west  - Western longitude bound (degrees).
+   * @param {number} north - Northern latitude bound (degrees).
+   * @param {number} east  - Eastern longitude bound (degrees).
+   * @param {Object}  [opts]
+   * @param {boolean} [opts.majorOnly=false] - Restrict to major highway classes only.
+   * @param {number}  [opts.timeoutSec=25]   - Overpass server-side timeout.
+   * @returns {string} Overpass QL query body.
+   */
+
+  /**
+   * Parse an Overpass `out geom;` JSON response into internal road objects.
+   *
+   * Each OSM `way` element carries an inline `geometry` array of `{lat, lon}`
+   * objects, so no separate node look-up or osmtogeojson conversion is needed.
+   *
+   * Processing per way:
+   *  1. Extract [lon, lat] coordinate pairs.
+   *  2. Sub-sample long polylines to at most MAX_WAYPOINTS_PER_ROAD vertices.
+   *  3. Sample terrain height once at the first vertex (avoids per-vertex cost).
+   *  4. Convert to Cartesian3 waypoints and pre-compute inter-vertex distances.
+   *
+   * @param {Object} overpassData - Raw JSON response from the Overpass API.
+   * @param {Array}  overpassData.elements - Array of OSM elements.
+   * @returns {Array<{coords:number[][], type:string, waypoints:Cesium.Cartesian3[], segmentDist:number[]}>}
+   *   Parsed road objects ready for dot spawning.
+   */
+
+  function parseRoads(overpassData) {
+    if (!overpassData || !overpassData.elements) return [];
+
+    const roads = [];
+    for (const el of overpassData.elements) {
+      if (el.type !== 'way' || !el.geometry || el.geometry.length < 2) continue;
+
+      const rawCoords = el.geometry.map((g) => [g.lon, g.lat]);
+
+      // Sub-sample long polylines: keep every Nth vertex to stay within budget
+      const simplifyStep =
+        rawCoords.length > MAX_WAYPOINTS_PER_ROAD
+          ? Math.ceil(rawCoords.length / MAX_WAYPOINTS_PER_ROAD)
+          : 1;
+      const coords = [];
+      for (let i = 0; i < rawCoords.length; i += simplifyStep) {
+        coords.push(rawCoords[i]);
+      }
+
+      // Ensure the original endpoint is always preserved
+      const last = rawCoords[rawCoords.length - 1];
+      const tail = coords[coords.length - 1];
+      if (!tail || tail[0] !== last[0] || tail[1] !== last[1]) {
+        coords.push(last);
+      }
+
+      if (coords.length < 2) continue;
+
+      const type = el.tags?.highway || 'unclassified';
+      // One-way capture (field-test round 1: "a car would never go in
+      // reverse"): dots on one-way roads all travel the legal direction.
+      // OSM: oneway=yes/1/true → digitization order; '-1' → reversed;
+      // roundabouts are one-way by definition. 0 = two-way (alternate).
+      const onewayTag = el.tags?.oneway;
+      const oneway =
+        onewayTag === 'yes' ||
+        onewayTag === '1' ||
+        onewayTag === 'true' ||
+        el.tags?.junction === 'roundabout'
+          ? 1
+          : onewayTag === '-1'
+            ? -1
+            : 0;
+
+      // Sample terrain height once at the road start to avoid per-vertex cost
+      let baseHeight = 0;
+      const firstCoord = coords[0];
+      if (layerState._viewer?.scene?.sampleHeightSupported && firstCoord) {
+        const carto = Cesium.Cartographic.fromDegrees(
+          firstCoord[0],
+          firstCoord[1],
+        );
+        const sampled = layerState._viewer.scene.sampleHeight(carto);
+        if (Number.isFinite(sampled)) baseHeight = sampled;
+      }
+
+      // Pre-compute Cartesian3 waypoints (lon, lat, height) for fast lerp animation
+      const waypoints = coords.map(([lng, lat]) => {
+        const h = baseHeight + DOT_HEIGHT_OFFSET;
+        return Cesium.Cartesian3.fromDegrees(lng, lat, h);
+      });
+
+      // Pre-compute segment distances in meters for speed-to-t conversion
+      const segmentDist = [];
+      for (let i = 0; i < waypoints.length - 1; i++) {
+        segmentDist.push(
+          Cesium.Cartesian3.distance(waypoints[i], waypoints[i + 1]),
+        );
+      }
+
+      roads.push({ coords, type, oneway, waypoints, segmentDist });
+    }
+
+    return roads;
+  }
+
+  // ─── Road Length Estimation ────────────────────────────────
+
+  /**
+   * Estimate the total length of a road in meters from its degree-based coordinates.
+   *
+   * Uses Euclidean distance in degree-space then multiplies by the equatorial
+   * approximation of 111 km per degree. Accurate enough for dot density spacing
+   * but not for navigation.
+   *
+   * @param {number[][]} coords - Array of [lon, lat] pairs.
+   * @returns {number} Approximate road length in meters.
+   */
+
+  function estimateRoadLengthDeg(coords) {
+    let len = 0;
+    for (let i = 0; i < coords.length - 1; i++) {
+      const dx = coords[i + 1][0] - coords[i][0];
+      const dy = coords[i + 1][1] - coords[i][1];
+      len += Math.sqrt(dx * dx + dy * dy);
+    }
+    // Rough conversion: 1 degree ~ 111,000 meters at equator
+    return len * 111000;
+  }
+
+  // ─── Dot Spawning ──────────────────────────────────────────
+
+  /**
+   * Compute the ideal number of dots for a single road at a given camera altitude.
+   *
+   * Spacing increases with altitude so fewer dots are rendered when zoomed out.
+   * The result is further scaled by the road-type density multiplier and the
+   * user-adjustable `_densityScale`.
+   *
+   * @param {{coords:number[][], type:string}} road - Parsed road object.
+   * @param {number} altitude - Current camera altitude in meters.
+   * @returns {number} Ideal dot count (minimum 1).
+   */
+
+  function computeDotCount(road, altitude) {
+    // Live flow: closed roads carry zero traffic; congestion packs more dots.
+    // `road.flow` is only ever set in live mode, so the keyless path is
+    // untouched (flow stays undefined → multiplier 1, identical output).
+    const flow = layerState._liveMode ? road.flow : null;
+    if (flow?.closure) return 0;
+    // Strict data-integrity view: uncovered roads spawn nothing when hidden.
+    if (layerState._liveMode && !flow && layerState._uncoveredMode === 'hide')
+      return 0;
+
+    const lengthM = estimateRoadLengthDeg(road.coords);
+
+    // Altitude-adaptive spacing: closer camera = denser dots
+    let spacing;
+    if (altitude < 1000) spacing = 30;
+    else if (altitude < 3000) spacing = 80;
+    else if (altitude < 5000) spacing = 150;
+    else spacing = 250;
+
+    const mult =
+      (DENSITY_MULT[road.type] || 1) *
+      layerState._densityScale *
+      (flow
+        ? flowDensityMult(flow.level, { jamBoost: parts.style.jamDensityOn() })
+        : 1);
+    return Math.max(1, Math.floor((lengthM / spacing) * mult));
+  }
+
+  /**
+   * Distribute a fixed dot budget fairly across all visible roads.
+   *
+   * Algorithm:
+   *  1. Compute ideal dot count per road via `computeDotCount`.
+   *  2. Seed one dot to every road that wants at least one (fairness pass).
+   *  3. Distribute remaining budget proportionally to each road's ideal count.
+   *  4. Assign leftover dots (from floor rounding) to roads with the highest
+   *     fractional residuals (largest-remainder method).
+   *
+   * This prevents high-density motorways from starving smaller residential roads
+   * when the global MAX_DOTS cap is reached.
+   *
+   * @param {Array} roads    - Parsed road objects.
+   * @param {number} altitude - Camera altitude in meters (affects spacing).
+   * @param {number} dotCap   - Maximum total dots to allocate.
+   * @returns {number[]} Per-road dot budgets, same length as `roads`.
+   */
+
+  function allocateRoadDotBudgets(roads, altitude, dotCap) {
+    const planned = roads.map((road) => computeDotCount(road, altitude));
+    const budgets = new Array(roads.length).fill(0);
+    let remaining = Math.max(0, dotCap);
+
+    // Pass 1 — fairness seed: give one dot to every road (highest-demand first)
+    const firstPassOrder = planned
+      .map((count, index) => ({ count, index }))
+      .sort((a, b) => b.count - a.count);
+
+    for (const entry of firstPassOrder) {
+      if (remaining <= 0) break;
+      if (entry.count <= 0) continue;
+      budgets[entry.index] = 1;
+      remaining -= 1;
+    }
+
+    if (remaining <= 0) return budgets;
+
+    // Pass 2 — proportional distribution of the remaining budget
+    let totalRemainder = 0;
+    for (let i = 0; i < planned.length; i++) {
+      totalRemainder += Math.max(0, planned[i] - budgets[i]);
+    }
+    if (totalRemainder <= 0) return budgets;
+
+    const residuals = [];
+    let assigned = 0;
+    for (let i = 0; i < planned.length; i++) {
+      const cap = Math.max(0, planned[i] - budgets[i]);
+      if (cap <= 0) continue;
+      const ideal = (cap / totalRemainder) * remaining;
+      const add = Math.min(cap, Math.floor(ideal));
+      budgets[i] += add;
+      assigned += add;
+      residuals.push({ index: i, residual: ideal - add });
+    }
+
+    // Pass 3 — largest-remainder: hand out leftover dots from floor rounding
+    let leftover = remaining - assigned;
+    if (leftover > 0 && residuals.length > 0) {
+      residuals.sort((a, b) => b.residual - a.residual);
+      let cursor = 0;
+      while (leftover > 0 && residuals.length > 0) {
+        const idx = residuals[cursor % residuals.length].index;
+        if (budgets[idx] < planned[idx]) {
+          budgets[idx] += 1;
+          leftover -= 1;
+        }
+        cursor += 1;
+        // Safety valve: avoid infinite loop if all roads are already at their ideal
+        if (cursor > residuals.length * 3 && leftover > 0) break;
+      }
+    }
+
+    return budgets;
+  }
+
+  /**
+   * Derive the layer's honest feed presentation from its live-flow state.
+   *
+   * The three states a user can be in, and what each must read as:
+   *  - keyless → `mode:'sim'` (the manager maps that to a FALLBACK chip) with a
+   *    label that never claims live data;
+   *  - live and healthy → LIVE with real coverage;
+   *  - live but flow-down → an `error` string, so the chip degrades and says
+   *    the colors on screen are simulated. Never a stale "LIVE · N% cov".
+   *
+   * @param {Object} [input]
+   * @param {boolean} [input.liveMode] - `/api/tomtom/status` reported a key.
+   * @param {boolean} [input.fetching] - A viewport load is in flight.
+   * @param {string|null} [input.flowError] - `deriveTrafficFlowError` result, if any.
+   * @param {number} [input.coveragePct] - Matched-road coverage, 0–100.
+   * @param {boolean} [input.statusUnavailable] - The status probe itself failed.
+   * @returns {{mode:'live'|'sim', error:string|null, loadingLabel:string}}
+   */
+
+  function trafficFeedPresentation({
+    liveMode = false,
+    fetching = false,
+    flowError = null,
+    coveragePct = 0,
+    statusUnavailable = false,
+  } = {}) {
+    // `mode` is the CONFIGURED source (live key present vs keyless), not this
+    // instant's health — health rides on `error`. The qa-traffic harness pins
+    // that meaning.
+    const mode = liveMode ? 'live' : 'sim';
+    if (liveMode && flowError) {
+      // One string for both fields. The manager's meta line renders `error` and
+      // drops `loadingLabel` in its error branch, so the owner's SIMULATED copy
+      // has to BE the error text or the steady state reverts to a bare
+      // "TomTom daily budget reached" that never says what is on screen.
+      const degraded = `SIMULATED — ${flowError}`;
+      return { mode, error: degraded, loadingLabel: degraded };
+    }
+    if (liveMode) {
+      return {
+        mode,
+        error: null,
+        loadingLabel: fetching
+          ? 'syncing LIVE traffic flow'
+          : `LIVE · TomTom flow · ${coveragePct}% cov`,
+      };
+    }
+    // Keyless simulation — one terse line that names the mode and the remedy
+    // (owner's copy shape). The chip's own progress text carries "working";
+    // this line must never imply a live feed.
+    return {
+      mode,
+      error: null,
+      loadingLabel: statusUnavailable
+        ? 'SIMULATED — traffic service unreachable'
+        : 'SIMULATED — add TomTom key for live',
+    };
+  }
+
+  /**
+   * Apply late-arriving flow data to already-rendered dots without a respawn:
+   * color, jam size, and speed update in place; closed roads' dots hide.
+   * Density bunching intentionally waits for the next natural re-render —
+   * color and speed are the live signal, dot count is a refinement.
+   * @param {string} label - Render log label (for the console trace).
+   */
+
+  function recolorDotsInPlace(label) {
+    if (!layerState._liveMode || !layerState._dots.length) return;
+    layerState._bucketCounts = { free: 0, slow: 0, jam: 0, sim: 0 };
+    let closedDots = 0;
+    const now = Date.now();
+    for (const dot of layerState._dots) {
+      const flow = dot.road ? dot.road.flow : null;
+      if (flow?.closure) {
+        dot.point.show = false;
+        closedDots += 1;
+        continue;
+      }
+      const bucket = flow ? flowBucket(flow.level) : null;
+      dot.bucket = bucket;
+      dot.point.color = bucket
+        ? layerState._activeBucketColors[bucket]
+        : Cesium.Color.WHITE.withAlpha(0.85);
+      if (bucket === 'jam') {
+        dot.point.pixelSize =
+          parts.style.baseDotSize(dot.road?.type, bucket) +
+          1 +
+          parts.style.activeSizeDelta('jam');
+      } else if (bucket && parts.style.presetProfileActive()) {
+        // Preset profiles size-floor every bucket; the shipped normal path
+        // keeps its jam-only size touch (byte-identical behavior).
+        dot.point.pixelSize =
+          parts.style.baseDotSize(dot.road?.type, bucket) +
+          parts.style.activeSizeDelta(bucket);
+      }
+      // Late flow can move a dot between buckets — keep the preset halo in
+      // step (no-op writes under the normal profile, whose dots have none).
+      if (parts.style.presetProfileActive())
+        parts.style.applyOutline(dot.point, bucket);
+      dot.mps = dot.baseMps * (flow ? flowSpeedScale(flow.level) : 1);
+      // Late flow tags/untags stop-and-go creep + city-scale prominence the
+      // same way it rescales speed. Queue *positions* wait for the next
+      // natural re-render, like density bunching.
+      if (bucket === 'jam' && parts.style.jamDensityOn()) {
+        if (!dot.creep)
+          dot.creep = {
+            moving: Math.random() < 0.4,
+            until: now + Math.random() * 2000,
+          };
+        dot.point.scaleByDistance = new Cesium.NearFarScalar(
+          100,
+          1.5,
+          layerState._fadeScaleFar,
+          JAM_DOT_FAR_SCALE,
+        );
+        dot.point.disableDepthTestDistance = JAM_DOT_DEPTH_PUNCH;
+      } else {
+        dot.creep = null;
+      }
+      layerState._bucketCounts[bucket || 'sim'] += 1;
+    }
+    layerState._closedRoads = layerState._roads.reduce(
+      (n, r) => n + (r.flow?.closure ? 1 : 0),
+      0,
+    );
+    parts.rendering.rebuildHeatLines(
+      parts.rendering.visibleRoadsForAltitude(
+        layerState._roads,
+        layerState._lastRenderAltitude,
+      ),
+    );
+    console.log(
+      `[Data:Traffic] Flow recolor (${label}): ${layerState._dots.length} dots, closedDots=${closedDots}`,
+    );
+  }
+  return {
+    parseRoads,
+    estimateRoadLengthDeg,
+    computeDotCount,
+    allocateRoadDotBudgets,
+    trafficFeedPresentation,
+    recolorDotsInPlace,
+  };
+}

src/layers/traffic/policy.js

@@ -0,0 +1,215 @@
+import * as Cesium from 'cesium';
+
+/**
+ * @file Street Traffic — animated dots along OSM road polylines, colored by
+ * live TomTom congestion when a key is configured.
+ *
+ * Road geometry: OSM Overpass API (free, no auth). Fetches road polylines for
+ * the camera viewport, spawns PointPrimitives that lerp along pre-computed
+ * Cartesian3 waypoints. Camera-gated: only active below ~8 km altitude.
+ *
+ * Two modes (decided once per session via `/api/tomtom/status`):
+ *  - `sim` (keyless default): white dots at hardcoded per-road-class speeds —
+ *    the original simulation, byte-identical behavior.
+ *  - `live`: TomTom flow tiles (`flowTiles.js`) are matched onto the same
+ *    Overpass roads (`flowMatch.js`); matched roads color/slow/densify their
+ *    dots by real congestion (`trafficFlowStyle.js`), closed roads spawn no
+ *    dots, and unmatched roads keep the simulated white.
+ *
+ * Architecture overview:
+ *  - Camera-change listener triggers debounced road fetching per viewport tile.
+ *  - Fetch bounds center on the camera's look-at point (`trafficBounds.js`, C4).
+ *  - Roads are fetched in two passes: major-only (fast) then full graph (detailed).
+ *  - Fetched tiles are cached by clamped bounding-box key to avoid re-fetching.
+ *  - Dot budget allocation distributes a hard cap fairly across visible roads.
+ *  - Each dot lerps along pre-computed Cartesian3 waypoints every preRender frame.
+ *
+ * @module data/traffic
+ */
+
+/** @const {string} Proxy endpoint for Overpass API queries */
+
+export const OVERPASS_URL = '/api/overpass';
+
+/** @const {number} Meters — hide all traffic dots above this camera altitude */
+
+export const ACTIVATION_ALTITUDE = 8000;
+
+/** @const {number} Meters — above this altitude, only major roads are fetched */
+
+export const FAST_FETCH_ALTITUDE = 4500;
+
+/** @const {number} Milliseconds — debounce delay before fetching after camera settles */
+
+export const FETCH_DEBOUNCE = 320;
+
+/** @const {number} Meters — vertical offset to keep dots above clamped terrain surface */
+
+export const DOT_HEIGHT_OFFSET = 3.0;
+
+/** @const {number} Fraction (0-1) — skip re-fetch when viewport overlap exceeds this */
+
+export const OVERLAP_THRESHOLD = 0.6;
+
+/** @const {number} Hard cap on total rendered dot primitives for GPU/CPU performance */
+
+export const MAX_DOTS = 6000;
+
+/** @const {number} Polylines longer than this are simplified by sub-sampling */
+
+export const MAX_WAYPOINTS_PER_ROAD = 80;
+
+/** @const {number} Km — minimum viewport center shift before allowing refresh */
+
+export const MIN_CENTER_SHIFT_KM = 0.35;
+
+/**
+ * @const {number} Km — max great-circle distance the fetch center may sit from
+ * the camera nadir. Traffic only activates below ACTIVATION_ALTITUDE (8 km),
+ * so a look-at ground point farther than this is horizon-gazing and gets
+ * pulled back toward nadir (C4 oblique-bounds fix).
+ */
+
+export const MAX_LOOKAT_PULL_KM = 12;
+
+/**
+ * Development-only causal timing. Vite folds `import.meta.env.DEV` to false
+ * in production, so the query-string read, nullable trace branches, and every
+ * debug helper are removed from production builds. The remaining load-path
+ * selectors point directly at the original functions: no marks, listeners,
+ * observers, timers, counters, or per-road timing checks are installed.
+ */
+
+export const TRAFFIC_TIMING_ENABLED =
+  import.meta.env?.DEV &&
+  typeof window !== 'undefined' &&
+  new URLSearchParams(window.location.search).get('trafficDebug') === '1';
+
+/** @const {Object<string,number>} Speed in meters per second by highway tag (approximate real-world values) */
+
+export const SPEED_MPS = {
+  motorway: 25, // ~90 km/h
+  trunk: 20, // ~72 km/h
+  primary: 14, // ~50 km/h
+  secondary: 11, // ~40 km/h
+  tertiary: 8, // ~30 km/h
+  residential: 5, // ~18 km/h
+  unclassified: 5,
+};
+
+/** @const {Object<string,number>} Density multiplier — higher values spawn more dots on important roads */
+
+export const DENSITY_MULT = {
+  motorway: 3.0,
+  trunk: 2.5,
+  primary: 2.0,
+  secondary: 1.5,
+  tertiary: 1.0,
+  residential: 0.5,
+  unclassified: 0.4,
+};
+
+/** @const {Object<string,number>} Pixel size per road type (scaled up 25% for screen-recording visibility) */
+
+export const SIZE_BY_TYPE = {
+  motorway: 6,
+  trunk: 6,
+  primary: 5,
+  secondary: 5,
+  tertiary: 4,
+  residential: 4,
+  unclassified: 4,
+};
+
+/**
+ * Live-flow bucket colors (thresholds live in `trafficFlowStyle.js`):
+ * green free flow / amber slow / red jam, all at 0.9 alpha.
+ * Roads without flow data (`road.flow == null`) keep the sim's white.
+ * @const {Object<string, Cesium.Color>}
+ */
+
+export const FLOW_BUCKET_COLORS = {
+  free: Cesium.Color.fromCssColorString('#2ecc71').withAlpha(0.9),
+  slow: Cesium.Color.fromCssColorString('#f0b23e').withAlpha(0.9),
+  jam: Cesium.Color.fromCssColorString('#e05252').withAlpha(0.9),
+};
+
+// ─── Jam-viz prototype (live mode only — see 2026-07-21 design doc) ────────
+/** @const {number} Max congestion heat-line polylines per render (jam first). */
+
+export const HEAT_LINE_CAP = 400;
+
+/** @const {number} Px — glowing jam corridor line width. */
+
+export const HEAT_LINE_JAM_WIDTH = 9;
+
+/** @const {number} Px — flat slow corridor line width. */
+
+export const HEAT_LINE_SLOW_WIDTH = 4;
+
+/** @const {number} Jam heat-line alpha midpoint (pulse oscillates around it). */
+
+export const HEAT_JAM_BASE_ALPHA = 0.55;
+
+/** @const {number} Jam heat-line pulse amplitude (±, ~1.6 s period). */
+
+export const HEAT_JAM_PULSE_ALPHA = 0.2;
+
+/** @const {Cesium.Color} Jam corridor color (bucket red, alpha pulsed live). */
+
+export const HEAT_JAM_COLOR = Cesium.Color.fromCssColorString('#e05252');
+
+/** @const {Cesium.Color} Slow corridor color (bucket amber, faint + static). */
+
+export const HEAT_SLOW_COLOR =
+  Cesium.Color.fromCssColorString('#f0b23e').withAlpha(0.2);
+
+/**
+ * @const {number} Meters — jam dots depth-test-punch through the 3D tiles out
+ * to this camera distance so queues stay visible at city scale. The single
+ * start-of-road terrain sample puts much of a road below the rendered mesh
+ * at oblique city views (first A/B capture: 396 jam dots, zero visible), so
+ * the shipped 2 km window hides exactly the congestion this prototype is
+ * meant to surface. Live jam dots only; sim dots keep the shipped 2 km.
+ */
+
+export const JAM_DOT_DEPTH_PUNCH = 15000;
+
+/** @const {number} Far-distance scale floor for jam dots (shipped: 0.3). */
+
+export const JAM_DOT_FAR_SCALE = 0.55;
+
+/** @const {number} Speed multiplier while a stop-and-go jam dot bursts forward. */
+
+export const CREEP_BURST = 2.2;
+
+/** @const {number[]} Ms range a jam dot creeps forward before stopping. */
+
+export const CREEP_MOVE_MS = [1200, 3000];
+
+/** @const {number[]} Ms range a jam dot sits stopped between creeps. */
+
+export const CREEP_STOP_MS = [1500, 5000];
+
+/**
+ * @const {number} Minimum base pixel size for COLORED dots while a styled
+ * preset is active — residential-road dots spawn at 4 px and vanish into
+ * post-FX pixelation; presence is the dots' whole job there (owner round
+ * 2). Sim dots and the normal profile keep SIZE_BY_TYPE untouched.
+ */
+
+export const STYLED_MIN_BASE_PX = 5;
+
+/** @const {number} Maximum tile cache entries before LRU eviction */
+
+export const TILE_CACHE_MAX_ENTRIES = 64;
+
+/**
+ * Milliseconds the first dot paint will wait for flow data. Cached flow
+ * settles within this window (decode cache, 120 s TTL) and renders fully
+ * colored; a cold tile fetch loses the race, dots paint immediately in
+ * white, and recolorDotsInPlace applies the colors when flow arrives —
+ * field-test round 1's "takes forever to load" was the sequential wait.
+ */
+
+export const FLOW_RENDER_RACE_MS = 250;

src/layers/traffic/rendering.js

@@ -0,0 +1,318 @@
+import * as Cesium from 'cesium';
+import { flowBucket } from '../../data/trafficFlowStyle.js';
+import { trafficStyleProfile } from '../../data/trafficPresetStyle.js';
+import {
+  HEAT_LINE_CAP,
+  HEAT_JAM_COLOR,
+  HEAT_SLOW_COLOR,
+  HEAT_LINE_JAM_WIDTH,
+  HEAT_JAM_BASE_ALPHA,
+  HEAT_LINE_SLOW_WIDTH,
+  TRAFFIC_TIMING_ENABLED,
+  MAX_DOTS,
+} from './policy.js';
+
+export function createRendering({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  /**
+   * At high altitude only major roads render — shared by the render pass and
+   * the late-flow heat-line rebuild so lines never mark roads without dots.
+   * @param {Array} roads    - Parsed road objects.
+   * @param {number} altitude - Camera altitude in meters.
+   * @returns {Array} The roads visible at this altitude.
+   */
+
+  function visibleRoadsForAltitude(roads, altitude) {
+    return altitude > 5000
+      ? roads.filter(
+          (r) =>
+            r.type === 'motorway' || r.type === 'trunk' || r.type === 'primary',
+        )
+      : roads;
+  }
+
+  /** Remove both heat-line ground primitives from the scene. */
+
+  function removeHeatLines() {
+    if (layerState._heatJamPrim) {
+      layerState._viewer?.scene.groundPrimitives.remove(
+        layerState._heatJamPrim,
+      );
+      layerState._heatJamPrim = null;
+    }
+    if (layerState._heatSlowPrim) {
+      layerState._viewer?.scene.groundPrimitives.remove(
+        layerState._heatSlowPrim,
+      );
+      layerState._heatSlowPrim = null;
+    }
+    layerState._heatLineCount = 0;
+  }
+
+  /**
+   * Rebuild the congestion heat-line underlay (jam-viz heatline prototype):
+   * slow/jam roads drape a corridor line onto the rendered 3D tiles — glowing
+   * pulsing red for jam, faint flat amber for slow — with the dots animating
+   * on top. Two batched GroundPolylinePrimitives (one per bucket) so the jam
+   * batch pulses through one shared material. Capped at HEAT_LINE_CAP (jam
+   * first, longest first); overflow is logged. No-op in sim mode, when the
+   * heatline mode is off, or without ground-primitive support.
+   *
+   * @param {Array} roads - Road objects visible in the current render.
+   */
+
+  function rebuildHeatLines(roads) {
+    removeHeatLines();
+    if (
+      !layerState._viewer ||
+      !layerState._liveMode ||
+      !parts.style.heatlineOn()
+    )
+      return;
+    if (layerState._heatSupported === null) {
+      layerState._heatSupported = Cesium.GroundPolylinePrimitive.isSupported(
+        layerState._viewer.scene,
+      );
+      if (!layerState._heatSupported)
+        console.warn(
+          '[Data:Traffic] GroundPolylinePrimitive unsupported — heat-lines disabled',
+        );
+    }
+    if (!layerState._heatSupported) return;
+
+    const candidates = [];
+    for (const road of roads) {
+      const flow = road.flow;
+      if (!flow || flow.closure) continue;
+      const bucket = flowBucket(flow.level);
+      if (bucket === 'free') continue;
+      let len = 0;
+      for (const d of road.segmentDist) len += d;
+      candidates.push({ road, bucket, len });
+    }
+    candidates.sort((a, b) =>
+      a.bucket === b.bucket ? b.len - a.len : a.bucket === 'jam' ? -1 : 1,
+    );
+    const kept = candidates.slice(0, HEAT_LINE_CAP);
+
+    const instancesFor = (bucket, width) =>
+      kept
+        .filter((c) => c.bucket === bucket)
+        .map(
+          (c) =>
+            new Cesium.GeometryInstance({
+              geometry: new Cesium.GroundPolylineGeometry({
+                positions: c.road.waypoints,
+                width,
+              }),
+            }),
+        );
+
+    // Mono presets (NVG/FLIR/noir) discard hue — heat-lines re-encode in
+    // luminance like the dots: jam = white glow, slow = faint gray.
+    const monoHeat =
+      layerState._presetDots === 'on' &&
+      trafficStyleProfile(layerState._stylePreset) === 'mono';
+    const jamLineColor = monoHeat ? Cesium.Color.WHITE : HEAT_JAM_COLOR;
+    const slowLineColor = monoHeat
+      ? new Cesium.Color(0.7, 0.7, 0.7, HEAT_SLOW_COLOR.alpha)
+      : HEAT_SLOW_COLOR;
+
+    const jamInstances = instancesFor('jam', HEAT_LINE_JAM_WIDTH);
+    if (jamInstances.length) {
+      layerState._heatJamPrim = layerState._viewer.scene.groundPrimitives.add(
+        new Cesium.GroundPolylinePrimitive({
+          geometryInstances: jamInstances,
+          classificationType: Cesium.ClassificationType.CESIUM_3D_TILE,
+          appearance: new Cesium.PolylineMaterialAppearance({
+            material: Cesium.Material.fromType('PolylineGlow', {
+              color: jamLineColor.withAlpha(HEAT_JAM_BASE_ALPHA),
+              glowPower: 0.25,
+            }),
+          }),
+        }),
+      );
+    }
+    const slowInstances = instancesFor('slow', HEAT_LINE_SLOW_WIDTH);
+    if (slowInstances.length) {
+      layerState._heatSlowPrim = layerState._viewer.scene.groundPrimitives.add(
+        new Cesium.GroundPolylinePrimitive({
+          geometryInstances: slowInstances,
+          classificationType: Cesium.ClassificationType.CESIUM_3D_TILE,
+          appearance: new Cesium.PolylineMaterialAppearance({
+            material: Cesium.Material.fromType('Color', {
+              color: slowLineColor,
+            }),
+          }),
+        }),
+      );
+    }
+
+    layerState._heatLineCount = kept.length;
+    if (candidates.length > kept.length) {
+      console.log(
+        `[Data:Traffic] Heat-lines capped at ${HEAT_LINE_CAP} (${candidates.length} congested roads in view)`,
+      );
+    }
+  }
+
+  /**
+   * Clear existing dots and re-spawn them for the given road set and altitude.
+   *
+   * When zoomed out (>5 km), only major road types are rendered to reduce clutter.
+   * Dot budgets are allocated fairly across visible roads via `allocateRoadDotBudgets`.
+   *
+   * @param {Array} roads    - Parsed road objects to render.
+   * @param {number} altitude - Camera altitude in meters.
+   * @param {string} label    - Logging label (e.g. "Cache full", "Loaded major").
+   * @param {Object|null} [trace=null] - Development-only correlated load trace.
+   */
+
+  function renderRoadsForAltitude(roads, altitude, label, trace = null) {
+    const state =
+      TRAFFIC_TIMING_ENABLED && trace
+        ? parts.timing.trafficTimingRenderState(trace, label)
+        : null;
+    const renderId = state ? ++trace.renderSequence : null;
+    parts.animation.clearDots();
+    layerState._roads = roads;
+    layerState._lastRenderAltitude = altitude;
+
+    // At high altitude, drop minor roads to reduce visual noise
+    const filteredRoads = visibleRoadsForAltitude(roads, altitude);
+
+    // Closed roads spawn zero dots (computeDotCount/spawnDotsForRoad) — count
+    // them here so the closure signal is visible in stats even at zero dots.
+    layerState._closedRoads = layerState._liveMode
+      ? filteredRoads.reduce((n, r) => n + (r.flow?.closure ? 1 : 0), 0)
+      : 0;
+
+    // Fade distances must track the camera-to-AREA distance, not assume a
+    // nadir view: oblique pitches put the loaded roads many km away even at
+    // low altitude. Probe three roads and stretch the curves accordingly.
+    let areaDist = altitude;
+    if (layerState._viewer && filteredRoads.length) {
+      const probes = [
+        filteredRoads[0],
+        filteredRoads[Math.floor(filteredRoads.length / 2)],
+        filteredRoads[filteredRoads.length - 1],
+      ];
+      for (const probe of probes) {
+        const wp = probe?.waypoints?.[0];
+        if (wp)
+          areaDist = Math.max(
+            areaDist,
+            Cesium.Cartesian3.distance(
+              layerState._viewer.camera.positionWC,
+              wp,
+            ),
+          );
+      }
+    }
+    layerState._fadeScaleFar = Math.max(8000, areaDist * 1.5);
+    layerState._fadeTransFar = Math.max(10000, areaDist * 1.8);
+
+    const dotStart = state
+      ? parts.timing.trafficTimingMark(state, 'dot-construction-start', {
+          renderId,
+          renderLabel: label,
+          roadCount: roads.length,
+          visibleRoadCount: filteredRoads.length,
+        })
+      : null;
+    const roadBudgets = parts.model.allocateRoadDotBudgets(
+      filteredRoads,
+      altitude,
+      MAX_DOTS,
+    );
+    for (let i = 0; i < filteredRoads.length; i++) {
+      const road = filteredRoads[i];
+      const budget = roadBudgets[i] || 0;
+      if (budget <= 0) continue;
+      parts.animation.spawnDotsForRoad(road, altitude, budget);
+      if (layerState._dots.length >= MAX_DOTS) break;
+    }
+
+    const renderMetrics = state
+      ? {
+          renderId,
+          renderLabel: label,
+          roadCount: roads.length,
+          visibleRoadCount: filteredRoads.length,
+          dotCount: layerState._dots.length,
+        }
+      : null;
+    if (state) {
+      const dotEnd = parts.timing.trafficTimingMark(
+        state,
+        'dot-construction-end',
+        renderMetrics,
+      );
+      parts.timing.trafficTimingMeasure(
+        'dot-construction',
+        state,
+        dotStart,
+        dotEnd,
+        renderMetrics,
+      );
+    }
+
+    const heatStart = state
+      ? parts.timing.trafficTimingMark(
+          state,
+          'rebuild-heat-lines-start',
+          renderMetrics,
+        )
+      : null;
+    rebuildHeatLines(filteredRoads);
+    if (state) {
+      const heatEnd = parts.timing.trafficTimingMark(
+        state,
+        'rebuild-heat-lines-end',
+        {
+          ...renderMetrics,
+          heatLineCount: layerState._heatLineCount,
+        },
+      );
+      parts.timing.trafficTimingMeasure(
+        'rebuild-heat-lines',
+        state,
+        heatStart,
+        heatEnd,
+        {
+          ...renderMetrics,
+          heatLineCount: layerState._heatLineCount,
+        },
+      );
+    }
+
+    layerState._count = layerState._dots.length;
+    layerState._lastUpdate = Date.now();
+    console.log(
+      `[Data:Traffic] ${label}: ${layerState._count} dots (roads=${roads.length}, alt=${Math.round(altitude)}m)`,
+    );
+    if (state) {
+      const renderEnd = parts.timing.trafficTimingMark(
+        state,
+        'render-return',
+        renderMetrics,
+      );
+      parts.timing.scheduleTrafficTimingPostRender(
+        state,
+        renderEnd,
+        renderId,
+        renderMetrics,
+      );
+    }
+  }
+  return {
+    visibleRoadsForAltitude,
+    removeHeatLines,
+    rebuildHeatLines,
+    renderRoadsForAltitude,
+  };
+}

src/layers/traffic/source.js

@@ -0,0 +1,76 @@
+import { createFlowTileSource } from './flowSource.js';
+function buildOverpassQuery(
+  south,
+  west,
+  north,
+  east,
+  { majorOnly = false, timeoutSec = 25 } = {},
+) {
+  // Regex matches the OSM `highway` tag value against allowed road types
+  const regex = majorOnly
+    ? '^(motorway|trunk|primary|secondary)$'
+    : '^(motorway|trunk|primary|secondary|tertiary|residential|unclassified)$';
+  return `[out:json][timeout:${timeoutSec}];(way["highway"~"${regex}"](${south},${west},${north},${east}););out geom qt;`;
+}
+
+/** Supply road responses, flow availability and one decoded flow cache. */
+export function createTrafficSource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+} = {}) {
+  const flow = createFlowTileSource({ fetchImpl });
+  return {
+    ...flow,
+    async requestRoads(
+      { south, west, north, east },
+      { majorOnly = false, timeoutSec = 25, signal } = {},
+    ) {
+      if (
+        ![south, west, north, east].every(Number.isFinite) ||
+        south < -90 ||
+        north > 90 ||
+        west < -180 ||
+        east > 180 ||
+        north <= south ||
+        east <= west ||
+        north - south > 10 ||
+        east - west > 10 ||
+        !Number.isInteger(timeoutSec) ||
+        timeoutSec < 1 ||
+        timeoutSec > 30
+      )
+        throw new TypeError('A bounded road viewport and timeout are required');
+      signal?.throwIfAborted();
+      const query = buildOverpassQuery(south, west, north, east, {
+        majorOnly,
+        timeoutSec,
+      });
+      const response = await fetchImpl('/api/overpass', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+        body: 'data=' + encodeURIComponent(query),
+        signal,
+      });
+      signal?.throwIfAborted();
+      return {
+        ok: response.ok,
+        status: response.status,
+        headers: response.headers,
+        async json() {
+          const body = await response.json();
+          signal?.throwIfAborted();
+          return body;
+        },
+      };
+    },
+    async getStatus({ signal } = {}) {
+      signal?.throwIfAborted();
+      const response = await fetchImpl('/api/tomtom/status', { signal });
+      if (!response.ok) throw new Error('HTTP ' + response.status);
+      const status = await response.json();
+      signal?.throwIfAborted();
+      if (typeof status?.hasKey !== 'boolean')
+        throw new Error('Malformed traffic status');
+      return status;
+    },
+  };
+}

src/layers/traffic/source.test.mjs

@@ -0,0 +1,129 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { readFileSync } from 'node:fs';
+import { createTrafficSource } from './source.js';
+const bounds = { south: 30.267, west: -97.744, north: 30.268, east: -97.743 };
+const fixture = readFileSync(
+  new URL(
+    '../../data/fixtures/tomtom-flow-austin-12-935-1686.pbf',
+    import.meta.url,
+  ),
+);
+test('flow caches and diagnostics belong to their constructed source', async () => {
+  let requestsA = 0,
+    requestsB = 0;
+  const a = createTrafficSource({
+    fetchImpl: async () => {
+      requestsA++;
+      return new Response(fixture);
+    },
+  });
+  const b = createTrafficSource({
+    fetchImpl: async () => {
+      requestsB++;
+      return new Response(fixture);
+    },
+  });
+  const first = await a.fetchFlowForBounds(bounds);
+  assert.ok(first.length > 0);
+  await a.fetchFlowForBounds(bounds);
+  assert.equal(requestsA, 1);
+  assert.equal(b.getFlowSessionStats().tilesFetched, 0);
+  b.resetFlowTileCache();
+  await a.fetchFlowForBounds(bounds);
+  assert.equal(requestsA, 1);
+  await b.fetchFlowForBounds(bounds);
+  assert.equal(requestsB, 1);
+});
+test('a cancelled flow body cannot refill its source cache', async () => {
+  const controller = new AbortController();
+  let calls = 0;
+  const source = createTrafficSource({
+    fetchImpl: async () => ({
+      ok: true,
+      arrayBuffer: async () => {
+        calls++;
+        if (calls === 1) controller.abort();
+        return fixture;
+      },
+    }),
+  });
+  await assert.rejects(
+    source.fetchFlowForBounds(bounds, { signal: controller.signal }),
+    { name: 'AbortError' },
+  );
+  await source.fetchFlowForBounds(bounds);
+  assert.equal(
+    calls,
+    2,
+    'cancelled bytes were not admitted to the decode cache',
+  );
+});
+test('road requests have finite bounds and retain the two-pass query', async () => {
+  const calls = [];
+  const source = createTrafficSource({
+    fetchImpl: async (...args) => {
+      calls.push(args);
+      return new Response('{"elements":[]}');
+    },
+  });
+  await assert.rejects(
+    source.requestRoads({ ...bounds, north: Infinity }),
+    /bounded road viewport/,
+  );
+  await assert.rejects(
+    source.requestRoads(bounds, { timeoutSec: '25];out;' }),
+    /bounded road viewport/,
+  );
+  assert.equal(calls.length, 0);
+  await source.requestRoads(bounds, { majorOnly: true, timeoutSec: 8 });
+  assert.equal(calls[0][0], '/api/overpass');
+  const query = new URLSearchParams(calls[0][1].body).get('data');
+  assert.match(query, /\[timeout:8\]/);
+  assert.doesNotMatch(query, /residential/);
+  await source.requestRoads(bounds);
+  assert.match(
+    new URLSearchParams(calls[1][1].body).get('data'),
+    /residential/,
+  );
+});
+test('malformed availability is an unavailable source rather than a keyless response', async () => {
+  const source = createTrafficSource({
+    fetchImpl: async () => new Response('{}'),
+  });
+  await assert.rejects(source.getStatus(), /Malformed traffic status/);
+});
+
+test('traffic construction is inert and parameters belong to each layer', async () => {
+  const { createTrafficLayer } = await import('./index.js');
+  const source = createTrafficSource({
+    fetchImpl: () => assert.fail('construction fetched data'),
+  });
+  const services = { credits: {}, render: {} };
+  const a = createTrafficLayer({ services, source });
+  const b = createTrafficLayer({ services, source });
+  a.setParams({ densityScale: 2, speedScale: 3, uncoveredRoads: 'hide' });
+  assert.equal(a.getParams().densityScale, 2);
+  assert.equal(b.getParams().densityScale, 1);
+  assert.equal(b.getParams().speedScale, 1);
+  assert.equal(b.getParams().uncoveredRoads, 'sim');
+});
+
+test('road body parsing retains the source request cancellation signal', async () => {
+  const controller = new AbortController();
+  const source = createTrafficSource({
+    fetchImpl: async () => ({
+      ok: true,
+      status: 200,
+      headers: new Headers(),
+      json: async () => {
+        controller.abort();
+        return { elements: [] };
+      },
+    }),
+  });
+  const response = await source.requestRoads(bounds, {
+    signal: controller.signal,
+  });
+  await assert.rejects(response.json(), { name: 'AbortError' });
+});

src/layers/traffic/state.js

@@ -0,0 +1,274 @@
+import * as Cesium from 'cesium';
+import { FLOW_BUCKET_COLORS, TRAFFIC_TIMING_ENABLED } from './policy.js';
+
+export function createState({ services }) {
+  const layerState = {};
+
+  // ─── Module State ──────────────────────────────────────────
+  /** @type {Cesium.Viewer|null} */
+
+  layerState._viewer = null;
+
+  /** @type {Cesium.PointPrimitiveCollection|null} */
+
+  layerState._pointCollection = null;
+
+  /** @type {Array<{point:Cesium.PointPrimitive, waypoints:Cesium.Cartesian3[], segmentDist:number[], numSegments:number, segIdx:number, t:number, mps:number, direction:number, stoppedUntil:number}>} Active animated dots */
+
+  layerState._dots = [];
+
+  /** @type {Array<{coords:number[][], type:string, waypoints:Cesium.Cartesian3[], segmentDist:number[]}>} Parsed roads with pre-computed Cartesian3 waypoints */
+
+  layerState._roads = [];
+
+  /** @type {boolean} Whether the layer is currently enabled */
+
+  layerState._enabled = false;
+
+  /** @type {Function|null} Disposer returned by preRender event subscription */
+
+  layerState._preRenderRemover = null;
+
+  /** @type {Function|null} Disposer returned by camera.changed event subscription */
+
+  layerState._cameraRemover = null;
+
+  /** @type {ReturnType<typeof setTimeout>|null} Debounce timer for camera-change fetch */
+
+  layerState._fetchTimeout = null;
+
+  /** @type {{south:number,west:number,north:number,east:number}|null} Last fetched clamped bounds */
+
+  layerState._lastBounds = null;
+
+  /** @type {boolean} True while an Overpass fetch is in flight */
+
+  layerState._fetching = false;
+
+  /** @type {number} Current count of rendered dots */
+
+  layerState._count = 0;
+
+  /** @type {number|null} Timestamp of last successful render */
+
+  layerState._lastUpdate = null;
+
+  /** @type {number} Monotonic generation counter — incremented on each load to discard stale responses */
+
+  layerState._loadGeneration = 0;
+
+  /** @type {AbortController|null} Controller for the in-flight fetch, so it can be cancelled */
+
+  layerState._activeFetchAbort = null;
+
+  /** @type {number} User-adjustable density multiplier (clamped 0.2–2.5) */
+
+  layerState._densityScale = 1.0;
+
+  /** @type {number} User-adjustable speed multiplier (clamped 0.3–3.0) */
+
+  layerState._speedScale = 1.0;
+
+  /** @type {{lat:number,lon:number}|null} Center of last-fetched viewport for shift gating */
+
+  layerState._lastViewCenter = null;
+
+  /** @type {number|null} camera.percentageChanged value before we overrode it, restored on disable */
+
+  layerState._prevPercentageChanged = null;
+
+  /** @type {boolean} Live TomTom flow mode — true iff /api/tomtom/status reports a key */
+
+  layerState._liveMode = false;
+
+  /**
+   * Short user-facing reason live flow is currently unavailable, or null while
+   * healthy. Only ever set in live mode: keyless simulation is a designed
+   * fallback, not a fault, and must never read as an error.
+   * @type {string|null}
+   */
+
+  layerState._flowError = null;
+
+  /**
+   * True when `/api/tomtom/status` itself could not be reached, so the layer is
+   * simulating because it could not ask — not because the server said "no key".
+   * @type {boolean}
+   */
+
+  layerState._flowStatusUnavailable = false;
+
+  /**
+   * Flow requests this layer still owns. The 250 ms paint race lets a flow
+   * fetch outlive the road load that started it (cached roads settle
+   * instantly), so `_fetching` alone under-reports the work in flight: the
+   * loading batch would close with LOAD COMPLETE and a failure landing after
+   * it could never be announced. Counted, not boolean — recolor-after-timeout
+   * means two loads can overlap.
+   * @type {number}
+   */
+
+  layerState._flowPending = 0;
+
+  /**
+   * Rendered-dot counts per flow bucket (sim = white ambient, no flow data).
+   * Reset with the dots in clearDots; drives the data-panel diagnostics and
+   * the qa-traffic harness color assertions.
+   * @type {{free:number, slow:number, jam:number, sim:number}}
+   */
+
+  layerState._bucketCounts = { free: 0, slow: 0, jam: 0, sim: 0 };
+
+  /** @type {number} Roads in the current render skipped entirely as closed. */
+
+  layerState._closedRoads = 0;
+
+  /** @type {'sim'|'hide'} Live-mode treatment of roads without flow data. */
+
+  layerState._uncoveredMode = 'sim';
+
+  /**
+   * Jam-viz prototype mode: 'density' = deep-jam density boost + platoon queues
+   * + stop-and-go creep; 'heatline' = congestion corridor polylines; 'both';
+   * 'none' = shipped main behavior. Live mode only — the keyless simulation
+   * never has `road.flow`, so every jamViz path is unreachable there.
+   * Default 'density' — owner A/B verdict 2026-07-23 (heatline stays available
+   * via setParams).
+   * @type {'none'|'density'|'heatline'|'both'}
+   */
+
+  layerState._jamViz = 'density';
+
+  /**
+   * Congestion heat-lines are GroundPolylinePrimitive batches draped onto the
+   * rendered 3D tiles (ClassificationType.CESIUM_3D_TILE) — polylines at the
+   * dots' single-sample heights depth-fail under the mesh across an oblique
+   * city view (first A/B capture: 198 lines rendered, zero visible). One
+   * primitive per bucket so the jam batch can pulse via a single shared
+   * material uniform.
+   * @type {Cesium.GroundPolylinePrimitive|null}
+   */
+
+  layerState._heatJamPrim = null;
+
+  /** @type {Cesium.GroundPolylinePrimitive|null} Slow-bucket heat-line batch. */
+
+  layerState._heatSlowPrim = null;
+
+  /** @type {number} Heat-lines in the current render (stats). */
+
+  layerState._heatLineCount = 0;
+
+  /** @type {boolean|null} GroundPolylinePrimitive.isSupported, checked once. */
+
+  layerState._heatSupported = null;
+
+  /** @type {number} Altitude of the last render, for late-flow heat rebuilds. */
+
+  layerState._lastRenderAltitude = 0;
+
+  /**
+   * Active post-FX style (StyleManager preset name), synced from
+   * `document.documentElement.dataset.gevStyle` at init and the
+   * `gev:style-change` window event thereafter. Drives the preset-aware dot
+   * styling (`trafficPresetStyle.js`): NVG/FLIR/noir re-encode congestion in
+   * luminance + size (their shaders discard hue), retro/CRT gets saturated
+   * hues + a size boost to survive pixelation. 'normal' → shipped palette.
+   * @type {string}
+   */
+
+  layerState._stylePreset = 'normal';
+
+  /** @type {'on'|'off'} Kill switch for preset-aware dot styling (A/B). */
+
+  layerState._presetDots = 'on';
+
+  /** @type {boolean} gev:style-change listener bound (bind once per page). */
+
+  layerState._styleListenerBound = false;
+
+  /**
+   * Effective per-bucket dot colors: preset override when one applies, else
+   * the shipped FLOW_BUCKET_COLORS. Rebuilt on style/param change only —
+   * spawn/recolor/restyle all read from here, no per-dot allocation.
+   * @type {{free:Cesium.Color, slow:Cesium.Color, jam:Cesium.Color}}
+   */
+
+  layerState._activeBucketColors = { ...FLOW_BUCKET_COLORS };
+
+  /**
+   * Dot fade-out distances, recomputed per render from the camera-to-area
+   * distance. The original constants (8 km scale / 10 km translucency)
+   * assumed a nadir view; at oblique pitch the loaded area legitimately sits
+   * 7–12+ km from the CAMERA and every dot faded to invisible (field-test
+   * round 1: "the screen itself was empty").
+   */
+
+  layerState._fadeScaleFar = 8000;
+
+  layerState._fadeTransFar = 10000;
+
+  /** @type {Promise<void>|null} Session-cached status check (one fetch per session) */
+
+  layerState._flowStatusPromise = null;
+
+  /** @type {ReturnType<typeof setInterval>|null} Enable-time retry until the first load commits. */
+
+  layerState._enableKickTimer = null;
+
+  /** @type {number} 0–100 int — matched roads / roads with any flow candidates */
+
+  layerState._flowCoveragePct = 0;
+
+  /** @type {Function|null} Development-only camera moveEnd timing disposer. */
+
+  layerState._trafficTimingMoveEndRemover = null;
+
+  /** @type {Set<Function>|null} Development-only one-shot postRender disposers. */
+
+  layerState._trafficTimingPostRenderRemovers = null;
+
+  /** @type {{interactionId:number, timestamp:number}|null} Debug anchor for the pending load. */
+
+  layerState._trafficTimingCurrentAnchor = null;
+
+  /** @type {number} Development-only unique mark/trace sequence. */
+
+  layerState._trafficTimingSequence = 0;
+
+  /** @type {number} Development-only count of correlated trace objects created. */
+
+  layerState._trafficTimingTracesCreated = 0;
+
+  /** @type {number} Development-only count of loads dropped for missing/stale anchors. */
+
+  layerState._trafficTimingDroppedTraces = 0;
+
+  /**
+   * Tile cache keyed by "s,w,n,e" string.
+   * Each entry stores separately fetched major-only and full road sets
+   * so the major pass can be served from cache while a full fetch continues.
+   * @type {Map<string, {major: Array|null, full: Array|null}>}
+   */
+
+  layerState._tileCache = new Map();
+
+  /** Reusable scratch Cartesian3 to avoid per-frame allocation / GC pressure */
+
+  layerState._scratchLerp = new Cesium.Cartesian3();
+
+  // ─── Animation ─────────────────────────────────────────────
+
+  /** @type {number} Timestamp of the last animation tick (ms) */
+
+  layerState._lastAnimTime = 0;
+
+  /** @type {number} Running frame counter (for diagnostics) */
+
+  layerState._animFrame = 0;
+
+  // Disabled-path contract: these references resolve directly to the original
+  // functions. Instrumentation adds no load-path callbacks or per-item checks.
+
+  return layerState;
+}

src/layers/traffic/style.js

@@ -0,0 +1,156 @@
+import {
+  trafficStyleProfile,
+  presetSizeDelta,
+  presetDotRgba,
+  presetDotOutline,
+} from '../../data/trafficPresetStyle.js';
+import * as Cesium from 'cesium';
+import {
+  SIZE_BY_TYPE,
+  STYLED_MIN_BASE_PX,
+  FLOW_BUCKET_COLORS,
+} from './policy.js';
+
+export function createStyle({ state: layerState, services, parts, source }) {
+  /** @returns {boolean} A non-normal preset profile is active and enabled. */
+
+  function presetProfileActive() {
+    return (
+      layerState._presetDots === 'on' &&
+      trafficStyleProfile(layerState._stylePreset) !== 'normal'
+    );
+  }
+
+  /**
+   * Pixel-size delta the active preset adds for a bucket (0 when the kill
+   * switch is off or the profile is normal).
+   * @param {'free'|'slow'|'jam'|null} bucket - Flow bucket.
+   * @returns {number} Pixels to add on top of the shipped sizing.
+   */
+
+  function activeSizeDelta(bucket) {
+    return layerState._presetDots === 'on'
+      ? presetSizeDelta(layerState._stylePreset, bucket)
+      : 0;
+  }
+
+  /**
+   * Base pixel size for a dot: shipped SIZE_BY_TYPE, floored at
+   * STYLED_MIN_BASE_PX for colored dots while a styled preset is active.
+   * @param {string} roadType - OSM highway class.
+   * @param {'free'|'slow'|'jam'|null} bucket - Flow bucket (null = sim).
+   * @returns {number} Base pixel size before jam/preset deltas.
+   */
+
+  function baseDotSize(roadType, bucket) {
+    const base = SIZE_BY_TYPE[roadType] || 4;
+    return bucket && presetProfileActive()
+      ? Math.max(base, STYLED_MIN_BASE_PX)
+      : base;
+  }
+
+  /** Recompute `_activeBucketColors` from the active style + kill switch. */
+
+  function refreshBucketColors() {
+    for (const bucket of ['free', 'slow', 'jam']) {
+      const rgba =
+        layerState._presetDots === 'on'
+          ? presetDotRgba(layerState._stylePreset, bucket)
+          : null;
+      layerState._activeBucketColors[bucket] = rgba
+        ? new Cesium.Color(rgba[0] / 255, rgba[1] / 255, rgba[2] / 255, rgba[3])
+        : FLOW_BUCKET_COLORS[bucket];
+    }
+  }
+
+  /**
+   * Apply the active preset's dark-halo outline to a colored dot (or clear
+   * it back to the shipped no-outline state). NVG's auto-gain saturates the
+   * scene, so brightness alone cannot separate a dot from a bright road —
+   * the dark ring restores local contrast through every luma-mapping shader.
+   * @param {Cesium.PointPrimitive} point - The dot primitive.
+   * @param {'free'|'slow'|'jam'|null} bucket - Flow bucket (null = sim).
+   */
+
+  function applyOutline(point, bucket) {
+    const spec =
+      layerState._presetDots === 'on'
+        ? presetDotOutline(layerState._stylePreset, bucket)
+        : null;
+    if (spec) {
+      point.outlineColor = new Cesium.Color(
+        spec.rgba[0] / 255,
+        spec.rgba[1] / 255,
+        spec.rgba[2] / 255,
+        spec.rgba[3],
+      );
+      point.outlineWidth = spec.width;
+    } else {
+      point.outlineWidth = 0;
+    }
+  }
+
+  /**
+   * Re-apply dot styling in place after a style/param change: colored dots
+   * get the (new) effective bucket color and size; sim (white) dots are
+   * never touched. No refetch, no respawn — heat-lines rebuild for their
+   * per-preset colors.
+   */
+
+  function restyleDotsInPlace() {
+    refreshBucketColors();
+    if (!layerState._dots.length && !layerState._heatLineCount) return;
+    for (const dot of layerState._dots) {
+      const bucket = dot.bucket;
+      if (!bucket) continue; // sim/uncovered dots stay byte-identical
+      dot.point.color = layerState._activeBucketColors[bucket];
+      dot.point.pixelSize =
+        baseDotSize(dot.road?.type, bucket) +
+        (bucket === 'jam' ? 1 : 0) +
+        activeSizeDelta(bucket);
+      applyOutline(dot.point, bucket);
+    }
+    parts.rendering.rebuildHeatLines(
+      parts.rendering.visibleRoadsForAltitude(
+        layerState._roads,
+        layerState._lastRenderAltitude,
+      ),
+    );
+  }
+
+  /**
+   * Adopt a new active style preset (from the gev:style-change event or the
+   * dataset read at init) and restyle live dots immediately.
+   * @param {string|null|undefined} name - StyleManager preset name.
+   */
+
+  function setStylePreset(name) {
+    const next = typeof name === 'string' && name ? name : 'normal';
+    if (next === layerState._stylePreset) return;
+    layerState._stylePreset = next;
+    restyleDotsInPlace();
+  }
+
+  /** @returns {boolean} Density/queue/creep prototype active. */
+
+  function jamDensityOn() {
+    return layerState._jamViz === 'density' || layerState._jamViz === 'both';
+  }
+
+  /** @returns {boolean} Heat-line prototype active. */
+
+  function heatlineOn() {
+    return layerState._jamViz === 'heatline' || layerState._jamViz === 'both';
+  }
+  return {
+    presetProfileActive,
+    activeSizeDelta,
+    baseDotSize,
+    refreshBucketColors,
+    applyOutline,
+    restyleDotsInPlace,
+    setStylePreset,
+    jamDensityOn,
+    heatlineOn,
+  };
+}

src/layers/traffic/timing.js

@@ -0,0 +1,479 @@
+import * as Cesium from 'cesium';
+import {
+  TRAFFIC_TIMING_ENABLED,
+  MAX_WAYPOINTS_PER_ROAD,
+  DOT_HEIGHT_OFFSET,
+} from './policy.js';
+
+export function createTiming({ state: layerState, services, parts, source }) {
+  /**
+   * Return development timing counters for the capture harness and inertness test.
+   * This named export is unused by the application and removed from production.
+   * @returns {{enabled:boolean, marksInstalled:number, traceObjectsCreated:number,
+   *   uncorrelatedTracesDropped:number}}
+   */
+
+  function getTrafficTimingDiagnostics() {
+    return {
+      enabled: Boolean(TRAFFIC_TIMING_ENABLED),
+      marksInstalled: layerState._trafficTimingMoveEndRemover ? 1 : 0,
+      traceObjectsCreated: layerState._trafficTimingTracesCreated,
+      uncorrelatedTracesDropped: layerState._trafficTimingDroppedTraces,
+    };
+  }
+
+  // ─── Development-only causal timing ───────────────────────
+
+  /**
+   * Return (and optionally update) the current trace's state for a render pass.
+   * This function is only reachable when `TRAFFIC_TIMING_ENABLED` is true.
+   *
+   * @param {Object|null} trace - Correlated load trace.
+   * @param {'major'|'full'} pass - Road-fetch/render pass.
+   * @param {string} [source] - Client cache or proxy/network source.
+   * @returns {Object|null} Mutable pass timing state.
+   */
+
+  function trafficTimingPass(trace, pass, source) {
+    if (!trace) return null;
+    let state = trace.passes.get(pass);
+    if (!state) {
+      state = {
+        trace,
+        pass,
+        source: source || 'unknown',
+        proxyCache: null,
+        proxyUpstream: null,
+      };
+      trace.passes.set(pass, state);
+    } else if (source) {
+      state.source = source;
+    }
+    return state;
+  }
+
+  /** Build a structured-clone-safe detail object for User Timing entries. */
+
+  function trafficTimingDetail(state, segment, extra = {}) {
+    return {
+      trafficTiming: true,
+      segment,
+      traceId: state?.trace?.id ?? null,
+      interactionId: state?.trace?.interactionId ?? null,
+      cameraChangeTimestamp: state?.trace?.cameraChangeTimestamp ?? null,
+      generation: state?.trace?.generation ?? null,
+      cacheKey: state?.trace?.cacheKey ?? null,
+      pass: state?.pass || 'load',
+      source: state?.source || 'unknown',
+      proxyCache: state?.proxyCache || null,
+      proxyUpstream: state?.proxyUpstream || null,
+      ...extra,
+    };
+  }
+
+  /** Add a uniquely named User Timing mark and return its name. */
+
+  function trafficTimingMark(state, phase, extra = {}, startTime) {
+    const traceId = state?.trace?.id ?? 'interaction';
+    const pass = state?.pass || 'load';
+    const name = `traffic:${traceId}:${pass}:${phase}:${++layerState._trafficTimingSequence}`;
+    const options = { detail: trafficTimingDetail(state, phase, extra) };
+    if (Number.isFinite(startTime)) options.startTime = startTime;
+    performance.mark(name, options);
+    return name;
+  }
+
+  /** Emit a named User Timing measure between two marks. */
+
+  function trafficTimingMeasure(segment, state, start, end, extra = {}) {
+    performance.measure(`traffic:${segment}:${state?.pass || 'load'}`, {
+      start,
+      end,
+      detail: trafficTimingDetail(state, segment, extra),
+    });
+  }
+
+  /** Emit an aggregate-duration measure without pretending its work was contiguous. */
+
+  function trafficTimingAggregate(
+    segment,
+    state,
+    anchorTime,
+    duration,
+    extra = {},
+  ) {
+    const start = trafficTimingMark(
+      state,
+      `${segment}-aggregate-start`,
+      extra,
+      anchorTime,
+    );
+    const end = trafficTimingMark(
+      state,
+      `${segment}-aggregate-end`,
+      extra,
+      anchorTime + duration,
+    );
+    trafficTimingMeasure(segment, state, start, end, {
+      aggregate: true,
+      ...extra,
+    });
+  }
+
+  /** Clear only this module's stale User Timing entries before a new debug run. */
+
+  function clearTrafficTimingEntries() {
+    const markNames = new Set(
+      performance
+        .getEntriesByType('mark')
+        .filter((entry) => entry.name.startsWith('traffic:'))
+        .map((entry) => entry.name),
+    );
+    const measureNames = new Set(
+      performance
+        .getEntriesByType('measure')
+        .filter((entry) => entry.name.startsWith('traffic:'))
+        .map((entry) => entry.name),
+    );
+    for (const name of markNames) performance.clearMarks(name);
+    for (const name of measureNames) performance.clearMeasures(name);
+  }
+
+  /** Return the stable User Timing mark name for a scheduling interaction. */
+
+  function trafficTimingCameraChangeMarkName(interactionId) {
+    return `traffic:interaction:${interactionId}:last-camera-change`;
+  }
+
+  /** Mint and mark the exact camera-change interaction that armed a debounced load. */
+
+  function markTrafficTimingCameraChange() {
+    const interactionId = ++layerState._trafficTimingSequence;
+    const timestamp = performance.now();
+    const anchor = { interactionId, timestamp };
+    layerState._trafficTimingCurrentAnchor = anchor;
+    performance.mark(trafficTimingCameraChangeMarkName(interactionId), {
+      startTime: timestamp,
+      detail: {
+        trafficTiming: true,
+        segment: 'last-camera-change',
+        interactionId,
+        timestamp,
+      },
+    });
+    return anchor;
+  }
+
+  /**
+   * Mark Cesium's diagnostic moveEnd notification. Cesium normally emits this
+   * about 500 ms after stillness, so fetch has typically already started and
+   * never waits for this boundary.
+   */
+
+  function markTrafficTimingMoveEnd() {
+    const diagnosticId = ++layerState._trafficTimingSequence;
+    const timestamp = performance.now();
+    const name = `traffic:diagnostic:${diagnosticId}:camera-move-end`;
+    performance.mark(name, {
+      startTime: timestamp,
+      detail: {
+        trafficTiming: true,
+        segment: 'camera-move-end',
+        diagnosticOnly: true,
+        cameraEventWaitTimeMs: 500,
+        fetchWaitsForMoveEnd: false,
+        timestamp,
+      },
+    });
+  }
+
+  /**
+   * Instrumented twin of `parseRoads`. Operation ordering and road output match
+   * the normal function; debug-only clocks accumulate synchronous height and
+   * waypoint-materialization time independently.
+   */
+
+  function parseRoadsTimed(overpassData, trace) {
+    /* TRACE_ONLY_BEGIN */
+    const _trafficTimingState = trafficTimingPass(
+      trace,
+      trace?.currentPass || 'full',
+    );
+    const _trafficTimingParseStartTime = performance.now();
+    const _trafficTimingParseStart = trafficTimingMark(
+      _trafficTimingState,
+      'road-parse-start',
+      {},
+      _trafficTimingParseStartTime,
+    );
+    /* TRACE_ONLY_END */
+    if (!overpassData || !overpassData.elements) {
+      /* TRACE_ONLY_BEGIN */
+      const _trafficTimingParseEnd = trafficTimingMark(
+        _trafficTimingState,
+        'road-parse-end',
+        { roadCount: 0 },
+      );
+      trafficTimingMeasure(
+        'road-parse-total',
+        _trafficTimingState,
+        _trafficTimingParseStart,
+        _trafficTimingParseEnd,
+        { roadCount: 0 },
+      );
+      trafficTimingAggregate(
+        'sample-height-total',
+        _trafficTimingState,
+        _trafficTimingParseStartTime,
+        0,
+        {
+          sampleHeightCalls: 0,
+          sampleHeightMeanMs: 0,
+          distinctCells: 0,
+          roadCount: 0,
+        },
+      );
+      trafficTimingAggregate(
+        'waypoint-materialization',
+        _trafficTimingState,
+        _trafficTimingParseStartTime,
+        0,
+        { roadCount: 0 },
+      );
+      /* TRACE_ONLY_END */
+      return [];
+    }
+
+    const roads = [];
+    /* TRACE_ONLY_BEGIN */
+    const _trafficTimingSampledCells = new Set();
+    let _trafficTimingSampleHeightCalls = 0;
+    let _trafficTimingSampleHeightMs = 0;
+    let _trafficTimingWaypointMaterializationMs = 0;
+    /* TRACE_ONLY_END */
+    for (const el of overpassData.elements) {
+      if (el.type !== 'way' || !el.geometry || el.geometry.length < 2) continue;
+
+      const rawCoords = el.geometry.map((g) => [g.lon, g.lat]);
+      const simplifyStep =
+        rawCoords.length > MAX_WAYPOINTS_PER_ROAD
+          ? Math.ceil(rawCoords.length / MAX_WAYPOINTS_PER_ROAD)
+          : 1;
+      const coords = [];
+      for (let i = 0; i < rawCoords.length; i += simplifyStep) {
+        coords.push(rawCoords[i]);
+      }
+
+      const last = rawCoords[rawCoords.length - 1];
+      const tail = coords[coords.length - 1];
+      if (!tail || tail[0] !== last[0] || tail[1] !== last[1]) {
+        coords.push(last);
+      }
+      if (coords.length < 2) continue;
+
+      const type = el.tags?.highway || 'unclassified';
+      const onewayTag = el.tags?.oneway;
+      const oneway =
+        onewayTag === 'yes' ||
+        onewayTag === '1' ||
+        onewayTag === 'true' ||
+        el.tags?.junction === 'roundabout'
+          ? 1
+          : onewayTag === '-1'
+            ? -1
+            : 0;
+
+      let baseHeight = 0;
+      const firstCoord = coords[0];
+      if (layerState._viewer?.scene?.sampleHeightSupported && firstCoord) {
+        /* TRACE_ONLY_BEGIN */
+        _trafficTimingSampleHeightCalls += 1;
+        _trafficTimingSampledCells.add(
+          `${firstCoord[1].toFixed(3)},${firstCoord[0].toFixed(3)}`,
+        );
+        /* TRACE_ONLY_END */
+        const carto = Cesium.Cartographic.fromDegrees(
+          firstCoord[0],
+          firstCoord[1],
+        );
+        /* TRACE_ONLY_BEGIN */
+        const _trafficTimingSampleStart = performance.now();
+        /* TRACE_ONLY_END */
+        const sampled = layerState._viewer.scene.sampleHeight(carto);
+        /* TRACE_ONLY_BEGIN */
+        _trafficTimingSampleHeightMs +=
+          performance.now() - _trafficTimingSampleStart;
+        /* TRACE_ONLY_END */
+        if (Number.isFinite(sampled)) baseHeight = sampled;
+      }
+
+      /* TRACE_ONLY_BEGIN */
+      const _trafficTimingMaterializeStart = performance.now();
+      /* TRACE_ONLY_END */
+      const waypoints = coords.map(([lng, lat]) => {
+        const h = baseHeight + DOT_HEIGHT_OFFSET;
+        return Cesium.Cartesian3.fromDegrees(lng, lat, h);
+      });
+      const segmentDist = [];
+      for (let i = 0; i < waypoints.length - 1; i++) {
+        segmentDist.push(
+          Cesium.Cartesian3.distance(waypoints[i], waypoints[i + 1]),
+        );
+      }
+      /* TRACE_ONLY_BEGIN */
+      _trafficTimingWaypointMaterializationMs +=
+        performance.now() - _trafficTimingMaterializeStart;
+      /* TRACE_ONLY_END */
+
+      roads.push({ coords, type, oneway, waypoints, segmentDist });
+    }
+
+    /* TRACE_ONLY_BEGIN */
+    const _trafficTimingMetrics = {
+      roadCount: roads.length,
+      sampleHeightCalls: _trafficTimingSampleHeightCalls,
+      sampleHeightMeanMs: _trafficTimingSampleHeightCalls
+        ? _trafficTimingSampleHeightMs / _trafficTimingSampleHeightCalls
+        : 0,
+      distinctCells: _trafficTimingSampledCells.size,
+    };
+    trafficTimingAggregate(
+      'sample-height-total',
+      _trafficTimingState,
+      _trafficTimingParseStartTime,
+      _trafficTimingSampleHeightMs,
+      _trafficTimingMetrics,
+    );
+    trafficTimingAggregate(
+      'waypoint-materialization',
+      _trafficTimingState,
+      _trafficTimingParseStartTime,
+      _trafficTimingWaypointMaterializationMs,
+      _trafficTimingMetrics,
+    );
+    const _trafficTimingParseEnd = trafficTimingMark(
+      _trafficTimingState,
+      'road-parse-end',
+      _trafficTimingMetrics,
+    );
+    trafficTimingMeasure(
+      'road-parse-total',
+      _trafficTimingState,
+      _trafficTimingParseStart,
+      _trafficTimingParseEnd,
+      _trafficTimingMetrics,
+    );
+    /* TRACE_ONLY_END */
+    return roads;
+  }
+
+  /** Resolve a render label into its correlated pass and data source. */
+
+  function trafficTimingRenderState(trace, label) {
+    const pass = label.toLowerCase().includes('major') ? 'major' : 'full';
+    const source = label.startsWith('Cache') ? 'client-cache' : 'proxy';
+    return trafficTimingPass(trace, pass, source);
+  }
+
+  /** Record the first Cesium postRender following a completed dot render. */
+
+  function scheduleTrafficTimingPostRender(
+    state,
+    renderEnd,
+    renderId,
+    renderMetrics,
+  ) {
+    if (!layerState._viewer?.scene) return;
+    let remove = null;
+    remove = layerState._viewer.scene.postRender.addEventListener(() => {
+      remove?.();
+      layerState._trafficTimingPostRenderRemovers?.delete(remove);
+      const visibleTime = performance.now();
+      const postRender = trafficTimingMark(
+        state,
+        'next-post-render',
+        {
+          renderId,
+          ...renderMetrics,
+        },
+        visibleTime,
+      );
+      const firstVisible = trafficTimingMark(
+        state,
+        'first-visible-pixel',
+        {
+          renderId,
+          visibleBoundary: 'next-postRender',
+          ...renderMetrics,
+        },
+        visibleTime,
+      );
+      trafficTimingMeasure(
+        'render-to-post-render',
+        state,
+        renderEnd,
+        postRender,
+        {
+          renderId,
+          visibleBoundary: 'next-postRender',
+          ...renderMetrics,
+        },
+      );
+      trafficTimingMeasure(
+        'last-camera-change-to-first-visible',
+        state,
+        state.trace.cameraChangeMark,
+        firstVisible,
+        { renderId, visibleBoundary: 'next-postRender', ...renderMetrics },
+      );
+    });
+    layerState._trafficTimingPostRenderRemovers?.add(remove);
+  }
+
+  /** Start a scheduling-correlated debug trace, or count and drop an unpaired load. */
+
+  async function loadRoadsForBoundsTimed(bounds, altitude, expectedAnchor) {
+    const generation = layerState._loadGeneration + 1;
+    if (
+      !expectedAnchor ||
+      expectedAnchor !== layerState._trafficTimingCurrentAnchor
+    ) {
+      layerState._trafficTimingDroppedTraces += 1;
+      await parts.ingestion.loadRoadsForBounds(bounds, altitude);
+      return;
+    }
+    layerState._trafficTimingCurrentAnchor = null;
+    const clamped = parts.viewport.clampBounds(bounds);
+    const trace = {
+      id: ++layerState._trafficTimingSequence,
+      interactionId: expectedAnchor.interactionId,
+      cameraChangeTimestamp: expectedAnchor.timestamp,
+      cameraChangeMark: trafficTimingCameraChangeMarkName(
+        expectedAnchor.interactionId,
+      ),
+      generation,
+      cacheKey: `${clamped.south.toFixed(4)},${clamped.west.toFixed(4)},${clamped.north.toFixed(4)},${clamped.east.toFixed(4)}`,
+      currentPass: null,
+      renderSequence: 0,
+      passes: new Map(),
+    };
+    layerState._trafficTimingTracesCreated += 1;
+    await parts.ingestion.loadRoadsForBounds(bounds, altitude, trace);
+  }
+  return {
+    getTrafficTimingDiagnostics,
+    trafficTimingPass,
+    trafficTimingDetail,
+    trafficTimingMark,
+    trafficTimingMeasure,
+    trafficTimingAggregate,
+    clearTrafficTimingEntries,
+    trafficTimingCameraChangeMarkName,
+    markTrafficTimingCameraChange,
+    markTrafficTimingMoveEnd,
+    parseRoadsTimed,
+    trafficTimingRenderState,
+    scheduleTrafficTimingPostRender,
+    loadRoadsForBoundsTimed,
+  };
+}

src/layers/traffic/viewport.js

@@ -0,0 +1,241 @@
+import * as Cesium from 'cesium';
+import {
+  deriveFetchCenter,
+  clampBoundsAroundCenter,
+} from '../../data/trafficBounds.js';
+import {
+  MAX_LOOKAT_PULL_KM,
+  ACTIVATION_ALTITUDE,
+  OVERLAP_THRESHOLD,
+  MIN_CENTER_SHIFT_KM,
+  TRAFFIC_TIMING_ENABLED,
+  FETCH_DEBOUNCE,
+} from './policy.js';
+
+export function createViewport({ state: layerState, services, parts, source }) {
+  // ─── Camera Monitoring ─────────────────────────────────────
+
+  /**
+   * Get the current camera altitude in meters above the ellipsoid.
+   * @returns {number} Camera height in meters, or Infinity if unavailable.
+   */
+
+  function getCameraAltitude() {
+    const carto = layerState._viewer.camera.positionCartographic;
+    return carto ? carto.height : Infinity;
+  }
+
+  /**
+   * Compute the current camera view rectangle in degrees.
+   * @returns {{south:number, west:number, north:number, east:number}|null}
+   *   Bounding box in degrees, or null if the rectangle cannot be computed.
+   */
+
+  function getViewBounds() {
+    const rect = layerState._viewer.camera.computeViewRectangle();
+    if (!rect) return null;
+    return {
+      south: Cesium.Math.toDegrees(rect.south),
+      west: Cesium.Math.toDegrees(rect.west),
+      north: Cesium.Math.toDegrees(rect.north),
+      east: Cesium.Math.toDegrees(rect.east),
+    };
+  }
+
+  /**
+   * Derive the road-fetch center from the camera's look-at ground point.
+   *
+   * C4 fix: at oblique pitch `computeViewRectangle()` spans toward the horizon,
+   * so its midpoint can sit tens of km from what the user is looking at. Instead
+   * we pick the ellipsoid under the canvas center (`camera.pickEllipsoid` — this
+   * works with the globe hidden under Google 3D tiles, where `scene.globe.pick`
+   * is NOT reliable), fall back to the camera nadir on a sky/horizon look, and
+   * pull horizon-gaze hits back to MAX_LOOKAT_PULL_KM from nadir.
+   *
+   * @returns {{lat:number, lon:number, source:string}|null} Fetch center in
+   *   degrees, or null when the camera position is unavailable.
+   */
+
+  function getFetchCenter() {
+    const carto = layerState._viewer.camera.positionCartographic;
+    if (!carto) return null;
+    const nadirLat = Cesium.Math.toDegrees(carto.latitude);
+    const nadirLon = Cesium.Math.toDegrees(carto.longitude);
+
+    let hitLat;
+    let hitLon;
+    const canvas = layerState._viewer.scene.canvas;
+    const width = canvas.clientWidth || canvas.width;
+    const height = canvas.clientHeight || canvas.height;
+    if (width > 0 && height > 0) {
+      const hit = layerState._viewer.camera.pickEllipsoid(
+        new Cesium.Cartesian2(width / 2, height / 2),
+        Cesium.Ellipsoid.WGS84,
+      );
+      if (hit) {
+        const hitCarto = Cesium.Cartographic.fromCartesian(hit);
+        hitLat = Cesium.Math.toDegrees(hitCarto.latitude);
+        hitLon = Cesium.Math.toDegrees(hitCarto.longitude);
+      }
+    }
+
+    return deriveFetchCenter({
+      nadirLat,
+      nadirLon,
+      hitLat,
+      hitLon,
+      maxPullKm: MAX_LOOKAT_PULL_KM,
+    });
+  }
+
+  /**
+   * Compute the geographic center of a bounding box.
+   * @param {{south:number, west:number, north:number, east:number}} bounds
+   * @returns {{lat:number, lon:number}} Center point in degrees.
+   */
+
+  function getBoundsCenter(bounds) {
+    return {
+      lat: (bounds.south + bounds.north) / 2,
+      lon: (bounds.west + bounds.east) / 2,
+    };
+  }
+
+  /**
+   * Approximate great-circle distance between two points in kilometres.
+   *
+   * Uses an equirectangular projection (cosine correction on longitude)
+   * with the 111 km/degree approximation. Sufficient for the small
+   * viewport-center shifts being compared.
+   *
+   * @param {{lat:number, lon:number}} a - First point.
+   * @param {{lat:number, lon:number}} b - Second point.
+   * @returns {number} Distance in kilometres.
+   */
+
+  function distanceKm(a, b) {
+    const dLat = (a.lat - b.lat) * 111;
+    const avgLat = ((a.lat + b.lat) / 2) * (Math.PI / 180);
+    const dLon = (a.lon - b.lon) * 111 * Math.cos(avgLat);
+    return Math.sqrt(dLat * dLat + dLon * dLon);
+  }
+
+  /**
+   * Check whether two bounding boxes overlap by at least a given fraction of
+   * the first box's area. Used to decide if a camera move is large enough to
+   * warrant a new road fetch.
+   *
+   * @param {{south:number, west:number, north:number, east:number}} a - Reference bounds.
+   * @param {{south:number, west:number, north:number, east:number}} b - Bounds to compare.
+   * @param {number} threshold - Minimum overlap fraction (0-1) relative to `a`.
+   * @returns {boolean} True if overlap area / a area >= threshold.
+   */
+
+  function boundsOverlap(a, b, threshold) {
+    // Compute the intersection rectangle
+    const overlapS = Math.max(a.south, b.south);
+    const overlapN = Math.min(a.north, b.north);
+    const overlapW = Math.max(a.west, b.west);
+    const overlapE = Math.min(a.east, b.east);
+
+    // No intersection if the rectangle is degenerate
+    if (overlapN <= overlapS || overlapE <= overlapW) return false;
+
+    const overlapArea = (overlapN - overlapS) * (overlapE - overlapW);
+    const aArea = (a.north - a.south) * (a.east - a.west);
+
+    return aArea > 0 && overlapArea / aArea >= threshold;
+  }
+
+  /**
+   * Clamp a bounding box to a maximum span to avoid overloading the Overpass API.
+   *
+   * The box is centered on the input's midpoint with each axis capped at 0.05
+   * degrees (~5.5 km at the equator). This keeps query area and response size
+   * manageable while still covering the visible neighbourhood.
+   *
+   * NOTE (C4): the camera-driven path in `onCameraChanged` centers on the
+   * derived look-at point via `clampBoundsAroundCenter` instead; this
+   * midpoint-centered variant remains as the internal re-clamp guard in
+   * `loadRoadsForBounds` (idempotent on already-clamped bounds).
+   *
+   * @param {{south:number, west:number, north:number, east:number}} bounds
+   * @returns {{south:number, west:number, north:number, east:number}} Clamped bounds.
+   */
+
+  function clampBounds(bounds) {
+    return clampBoundsAroundCenter(bounds, getBoundsCenter(bounds));
+  }
+
+  /**
+   * Camera-change handler — the main entry point for viewport-driven road loading.
+   *
+   * Gating logic:
+   *  1. If the camera is above ACTIVATION_ALTITUDE, clear all dots and bail.
+   *  2. Clamp the view bounds and compute the viewport center.
+   *  3. Skip the fetch if the new viewport significantly overlaps the last-fetched
+   *     bounds AND the center has shifted less than MIN_CENTER_SHIFT_KM. This
+   *     prevents redundant fetches during small pans.
+   *  4. Otherwise, debounce and schedule `loadRoadsForBounds`.
+   */
+
+  function onCameraChanged() {
+    if (!layerState._enabled) return;
+
+    const alt = getCameraAltitude();
+
+    // Above activation altitude — remove all traffic and stop.
+    // Also null the last-fetch gate: otherwise zooming back down to the SAME
+    // viewport hits the overlap/center-shift skip in step 3 and the dots
+    // (cleared here) never reload (H5). Clearing the gate forces a fresh fetch.
+    if (alt > ACTIVATION_ALTITUDE) {
+      parts.animation.clearDots();
+      layerState._lastBounds = null;
+      layerState._lastViewCenter = null;
+      return;
+    }
+
+    const bounds = getViewBounds();
+    if (!bounds) return;
+    // C4 fix: center the fetch box on the camera's look-at ground point (with
+    // nadir fallback + 12 km horizon-gaze pull-back), NOT the view rectangle's
+    // midpoint — at oblique pitch that midpoint drifts toward the horizon.
+    const fetchCenter = getFetchCenter();
+    const clamped = fetchCenter
+      ? clampBoundsAroundCenter(bounds, fetchCenter)
+      : clampBounds(bounds);
+    const center = getBoundsCenter(clamped);
+
+    // Skip re-fetch when viewport overlap is high and center shift is negligible
+    if (
+      layerState._lastBounds &&
+      layerState._lastViewCenter &&
+      boundsOverlap(clamped, layerState._lastBounds, OVERLAP_THRESHOLD) &&
+      distanceKm(center, layerState._lastViewCenter) < MIN_CENTER_SHIFT_KM
+    ) {
+      return;
+    }
+
+    // Debounce: wait for camera to settle before triggering a fetch. In debug
+    // captures the final changed event that arms this exact timeout is its
+    // causal anchor; Cesium's later moveEnd notification is diagnostic only.
+    const interactionAnchor = TRAFFIC_TIMING_ENABLED
+      ? parts.timing.markTrafficTimingCameraChange()
+      : null;
+    clearTimeout(layerState._fetchTimeout);
+    layerState._fetchTimeout = setTimeout(
+      () => layerState._loadRoadsForBounds(clamped, alt, interactionAnchor),
+      FETCH_DEBOUNCE,
+    );
+  }
+  return {
+    getCameraAltitude,
+    getViewBounds,
+    getFetchCenter,
+    getBoundsCenter,
+    distanceKm,
+    boundsOverlap,
+    clampBounds,
+    onCameraChanged,
+  };
+}

src/testSupport/readLayerSource.mjs

@@ -15,6 +15,8 @@ export function readLayerSource(file) {
       'rocketLaunches.js',
       'militaryInstallations.js',
       'militaryAwareness.js',
+      'traffic.js',
+      'bikeshare.js',
     ].includes(basename(path))
   )
     return readFileSync(path, 'utf8');
@@ -34,7 +36,11 @@ export function readLayerSource(file) {
                 ? '../layers/installations'
                 : basename(path) === 'militaryAwareness.js'
                   ? '../layers/awareness'
-                  : '../layers/vessels',
+                  : basename(path) === 'traffic.js'
+                    ? '../layers/traffic'
+                    : basename(path) === 'bikeshare.js'
+                      ? '../layers/bikeshare'
+                      : '../layers/vessels',
   );
   return readdirSync(directory)
     .filter((name) => name.endsWith('.js'))