diff --git a/changelog.d/1495-traffic-paired-sides.md b/changelog.d/1495-traffic-paired-sides.md
new file mode 100644
index 000000000..4007daf8e
--- /dev/null
+++ b/changelog.d/1495-traffic-paired-sides.md
@@ -0,0 +1,4 @@
+- Street Traffic gives the two TomTom `one_side` lines of one two-way street
+  a two-way direction's half share of simulated vehicles each, so the street
+  is no longer drawn twice as dense as the same street from OpenStreetMap
+  (quanticsoul4772, #1495).
diff --git a/docs/CURRENT-STATE.md b/docs/CURRENT-STATE.md
index 78e072695..006334930 100644
--- a/docs/CURRENT-STATE.md
+++ b/docs/CURRENT-STATE.md
@@ -6131,6 +6131,11 @@ easier to meet (detection is now on more often), but does not create it.
   TomTom draws only flow-tile lines with their own flow; roads without flow
   are not drawn and the status says so. A `full`-coverage flow line carries
   both travel directions, a `one_side` line the direction it is drawn in.
+  When an opposite-direction `one_side` line runs within 5 m of at least two
+  of three points a quarter, half and three quarters along a `one_side` line,
+  the two are one street's directions and each
+  gets a two-way direction's half share of dots, so the street is as dense as
+  one `full` line (#1455).
   OSM draws OpenFreeMap roads with flow matched onto them (below). Hybrid
   draws eligible TomTom motor-road lines and adds OpenFreeMap roads only where no eligible TomTom line
   runs within 35 m in the same travel direction (30 degrees), tested every
diff --git a/src/data/flowMatch.js b/src/data/flowMatch.js
index c050f6917..cc4fe2280 100644
--- a/src/data/flowMatch.js
+++ b/src/data/flowMatch.js
@@ -139,6 +139,7 @@ export function createFlowSegmentIndex(flowSegments) {
           roadType,
           level,
           closure,
+          flow,
         };
         const key = cellKey(
           Math.floor((seg.ax + seg.bx) / 2 / CELL_SIZE_M),
@@ -158,7 +159,8 @@ export function createFlowSegmentIndex(flowSegments) {
   const radius2 = MATCH_RADIUS_M * MATCH_RADIUS_M;
   /**
    * Nearest direction-compatible segment within 35 m of a projected point.
-   * `radiusFor(segment)` may tighten the radius per segment (never widen it).
+   * `radiusFor(segment)` may tighten the radius per segment (never widen it);
+   * 0 leaves the segment out.
    */
   function nearest(px, py, bearing, radiusFor = null) {
     const cx = Math.floor(px / CELL_SIZE_M);
@@ -177,7 +179,7 @@ export function createFlowSegmentIndex(flowSegments) {
           candidate = true; // within radius, bearing not yet checked
           if (radiusFor) {
             const radius = Math.min(MATCH_RADIUS_M, radiusFor(seg));
-            if (d2 > radius * radius) continue;
+            if (!(radius > 0) || d2 > radius * radius) continue;
           }
           const diff = bearingDiffDeg(seg.bearing, bearing);
           if (
diff --git a/src/layers/traffic/flowSource.js b/src/layers/traffic/flowSource.js
index f517c99bc..12e746e43 100644
--- a/src/layers/traffic/flowSource.js
+++ b/src/layers/traffic/flowSource.js
@@ -20,6 +20,19 @@ function tileFreshness(response) {
   };
 }
 
+/**
+ * Clip a flow line to a box. Every piece keeps its uncut line as `line`, so
+ * pieces of one line that doubles back are never paired with each other.
+ */
+function clipFlowSegment(segment, bbox) {
+  const line = segment.line || segment;
+  return clipTileLine(segment.coords, bbox).map((coords) => ({
+    ...segment,
+    coords,
+    line,
+  }));
+}
+
 /** Own one bounded decoded flow cache; every request still passes the server tile budget. */
 export function createFlowTileSource({
   fetchImpl = (...args) => globalThis.fetch(...args),
@@ -41,12 +54,7 @@ export function createFlowTileSource({
       entry?.release();
       const segments = decodeFlowTile(bytes, z, x, y, { strict: true })
         .filter(isDrivableFlowSegment)
-        .flatMap((segment) =>
-          clipTileLine(segment.coords, tileToBBox(z, x, y)).map((coords) => ({
-            ...segment,
-            coords,
-          })),
-        );
+        .flatMap((segment) => clipFlowSegment(segment, tileToBBox(z, x, y)));
       if (mark) freshness.set(segments, mark);
       return segments;
     },
@@ -87,12 +95,9 @@ export function createFlowTileSource({
     partial = result.partial;
     const segments = bounds.coverage
       ? result.tiles.flat()
-      : result.tiles.flat().flatMap((segment) =>
-          clipTileLine(segment.coords, bounds).map((coords) => ({
-            ...segment,
-            coords,
-          })),
-        );
+      : result.tiles
+          .flat()
+          .flatMap((segment) => clipFlowSegment(segment, bounds));
     const marks = result.tiles.map((tile) => freshness.get(tile) || {});
     const times = marks
       .map((mark) => mark.fetchedAt)
diff --git a/src/layers/traffic/roadModes.js b/src/layers/traffic/roadModes.js
index 05b7ba4f7..ce62f5e1f 100644
--- a/src/layers/traffic/roadModes.js
+++ b/src/layers/traffic/roadModes.js
@@ -35,6 +35,14 @@ const MIN_FILL_M = 40;
  * Same-class overlap keeps the full 35 m matcher radius.
  */
 const CLASS_MISMATCH_RADIUS_M = 15;
+/**
+ * Opposite-direction TomTom lines this close share one street: TomTom draws
+ * both directions of a two-way street a metre or two apart, and a divided
+ * carriageway's sides further apart.
+ */
+const PAIRED_SIDE_RADIUS_M = 5;
+/** Arc-length positions sampled along a `one_side` line for its partner. */
+const PAIRED_SIDE_SAMPLES = [0.25, 0.5, 0.75];
 const CONTROLLED_ACCESS_FLOW = new Set(['Motorway', 'International road']);
 const CONTROLLED_ACCESS_OSM = new Set(['motorway', 'trunk']);
 
@@ -85,20 +93,69 @@ export function isDrivableFlowSegment(segment) {
   );
 }
 
+/**
+ * Share of a `one_side` line's sample points (PAIRED_SIDE_SAMPLES) with an
+ * opposite-direction TomTom line beside them: TomTom draws a two-way street
+ * whose directions differ as two `one_side` lines on one centreline, while a
+ * divided carriageway's other side is further away than PAIRED_SIDE_RADIUS_M.
+ * @returns {number} Paired share in [0, 1].
+ */
+function pairedSampleShare(segment, index) {
+  const xs = [];
+  const ys = [];
+  const cum = [0];
+  for (const [lon, lat] of segment.coords) {
+    const [x, y] = index.project(lon, lat);
+    const i = xs.push(x) - 1;
+    ys.push(y);
+    if (i) cum.push(cum[i - 1] + Math.hypot(x - xs[i - 1], y - ys[i - 1]));
+  }
+  const length = cum[cum.length - 1];
+  if (!(length > 0)) return 0;
+  const line = segment.line || segment;
+  let paired = 0;
+  let i = 1;
+  for (const share of PAIRED_SIDE_SAMPLES) {
+    const target = share * length;
+    while (i < cum.length - 1 && cum[i] < target) i++;
+    const dx = xs[i] - xs[i - 1];
+    const dy = ys[i] - ys[i - 1];
+    const t = (target - cum[i - 1]) / (cum[i] - cum[i - 1] || 1);
+    const reverse = (Math.atan2(-dx, -dy) * 180) / Math.PI;
+    if (
+      index.nearest(
+        xs[i - 1] + dx * t,
+        ys[i - 1] + dy * t,
+        reverse,
+        // A line that doubles back beside itself, even clipped into pieces,
+        // is not its own pair.
+        (piece) =>
+          (piece.flow.line || piece.flow) === line ? 0 : PAIRED_SIDE_RADIUS_M,
+      ).best
+    )
+      paired++;
+  }
+  return paired / PAIRED_SIDE_SAMPLES.length;
+}
+
 /**
  * Convert decoded TomTom flow lines into road records that carry their own
  * flow. A line with `coverage: 'full'` describes both travel directions;
- * `one_side` lines describe the direction they are drawn in.
+ * `one_side` lines describe the direction they are drawn in. A `one_side`
+ * line paired with the opposite direction on the same street gets that
+ * direction's half share of dots, as a two-way road's direction does.
  * @param {Array<{coords:number[][], trafficLevel:number, roadType:string, closure:boolean, coverage?:string}>} segments
  * @returns {Array<object>} Road records (`directFlow: true`).
  */
 export function flowSegmentsToRoads(segments) {
-  return (segments || [])
-    .filter(
-      (segment) =>
-        segment?.coords?.length >= 2 && isDrivableFlowSegment(segment),
-    )
-    .map((segment) => ({
+  const drivable = (segments || []).filter(
+    (segment) => segment?.coords?.length >= 2 && isDrivableFlowSegment(segment),
+  );
+  const sides = createFlowSegmentIndex(
+    drivable.filter((segment) => segment.coverage !== 'full'),
+  );
+  return drivable.map((segment) => {
+    const road = {
       coordinates: segment.coords,
       type: FLOW_ROAD_TYPES[segment.roadType],
       drivable: true,
@@ -110,7 +167,15 @@ export function flowSegmentsToRoads(segments) {
       oneway: segment.coverage === 'full' ? 0 : 1,
       flow: { level: segment.trafficLevel, closure: segment.closure === true },
       directFlow: true,
-    }));
+    };
+    if (
+      segment.coverage !== 'full' &&
+      sides &&
+      pairedSampleShare(segment, sides) >= 0.5
+    )
+      road.densityWeight = 0.5;
+    return road;
+  });
 }
 
 /** Cut a projected polyline to the arc-length interval [from, to]. */
diff --git a/src/layers/traffic/roadModes.test.mjs b/src/layers/traffic/roadModes.test.mjs
index 1d1cd4986..228a9609c 100644
--- a/src/layers/traffic/roadModes.test.mjs
+++ b/src/layers/traffic/roadModes.test.mjs
@@ -1,10 +1,12 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
+import { PbfWriter } from 'pbf';
 import {
   flowSegmentsToRoads,
   resolveRoadMode,
   selectTrafficRoads,
 } from './roadModes.js';
+import { createFlowTileSource } from './flowSource.js';
 import { createTrafficSource } from './source.js';
 import { createTrafficLayer } from './index.js';
 import {
@@ -14,6 +16,7 @@ import {
   serializeStoredLayerState,
   parseStoredLayerState,
 } from '../../data/layerState.js';
+import { tileToBBox } from '../../data/tomtomTiles.js';
 
 const coordinates = [
   [-97.744, 30.267],
@@ -116,6 +119,133 @@ test('a full-coverage TomTom line is two-way and covers both OSM directions', ()
   assert.equal(roads.length, 1);
   assert.equal(roads[0].directFlow, true);
 });
+test("opposite TomTom sides of one street share a two-way street's dots", () => {
+  // About 1 m and 20 m north of `coordinates`, drawn westbound.
+  const back = (dLat) => ({
+    ...flow,
+    coords: coordinates.map(([lon, lat]) => [lon, lat + dLat]).reverse(),
+  });
+  const weights = (segments) =>
+    flowSegmentsToRoads(segments).map((road) => road.densityWeight ?? 1);
+  assert.deepEqual(weights([flow, back(0.00001)]), [0.5, 0.5]);
+  assert.deepEqual(weights([flow]), [1], 'a lone side keeps the one-way share');
+  assert.deepEqual(
+    weights([flow, back(0.00018)]),
+    [1, 1],
+    'a divided carriageway keeps one-way shares',
+  );
+  assert.deepEqual(
+    weights([
+      flow,
+      {
+        ...flow,
+        coords: coordinates.map(([lon, lat]) => [lon, lat + 0.00001]),
+      },
+    ]),
+    [1, 1],
+    'same-direction lines are not a pair',
+  );
+  assert.deepEqual(
+    weights([{ ...flow, coverage: 'full' }, back(0.00001)]),
+    [1, 1],
+    'a full-coverage line is not a side, and pairs with nothing',
+  );
+});
+test('a TomTom side paired along only part of its length keeps its share', () => {
+  // Westbound partners about 1 m north, from the start of `flow` to 30% and
+  // to 60% of its length: one or two of its three sample points.
+  const partner = (toLon) => ({
+    ...flow,
+    coords: [
+      [toLon, 30.26701],
+      [-97.744, 30.26701],
+    ],
+  });
+  const weightOfFlow = (other) =>
+    flowSegmentsToRoads([flow, other])[0].densityWeight ?? 1;
+  assert.equal(weightOfFlow(partner(-97.7434)), 1);
+  assert.equal(weightOfFlow(partner(-97.7428)), 0.5);
+});
+test('a TomTom side that doubles back beside itself is not its own pair', () => {
+  // East along `coordinates`, then back west about 1 m north.
+  const hairpin = {
+    ...flow,
+    coords: [...coordinates, [-97.742, 30.26701], [-97.744, 30.26701]],
+  };
+  assert.equal(flowSegmentsToRoads([hairpin])[0].densityWeight ?? 1, 1);
+});
+/** A flow tile of one-way Major roads; each line is [x, y, x, y, ...]. */
+function flowTile(lines) {
+  const writer = new PbfWriter();
+  writer.writeMessage(3, writeFlowLayer, lines);
+  return writer.finish();
+}
+function writeFlowLayer(lines, layer) {
+  layer.writeVarintField(15, 2);
+  layer.writeStringField(1, 'Traffic flow');
+  layer.writeVarintField(5, 4096);
+  layer.writeStringField(3, 'traffic_level');
+  layer.writeMessage(4, (_, value) => value.writeDoubleField(3, 0.6), null);
+  layer.writeStringField(3, 'road_type');
+  layer.writeMessage(
+    4,
+    (_, value) => value.writeStringField(1, 'Major road'),
+    null,
+  );
+  layer.writeStringField(3, 'traffic_road_coverage');
+  layer.writeMessage(
+    4,
+    (_, value) => value.writeStringField(1, 'one_side'),
+    null,
+  );
+  for (const xy of lines) {
+    // MoveTo one point, LineTo the rest, as zigzag deltas.
+    const geometry = [9];
+    for (let i = 0; i < xy.length; i++) {
+      if (i === 2) geometry.push(2 | ((xy.length / 2 - 1) << 3));
+      const delta = xy[i] - (i < 2 ? 0 : xy[i - 2]);
+      geometry.push((delta << 1) ^ (delta >> 31));
+    }
+    layer.writeMessage(
+      2,
+      (_, feature) => {
+        feature.writeVarintField(3, 2);
+        feature.writePackedVarint(2, [0, 0, 1, 1, 2, 2]);
+        feature.writePackedVarint(4, geometry);
+      },
+      null,
+    );
+  }
+}
+test('TomTom sides clipped by their tile and the view pair only with other lines', async () => {
+  // A one-way hairpin turning in the tile buffer, its arms one tile unit
+  // (about 2 m) apart, and a separate opposite pair. The tile clip cuts the
+  // hairpin into two arms; the view clip then cuts every line again.
+  const lines = [
+    [500, 1000, 4300, 1000, 4300, 1001, 500, 1001],
+    [-200, 3000, 4300, 3000],
+    [4300, 3001, -200, 3001],
+  ];
+  const source = createFlowTileSource({
+    fetchImpl: async () => new Response(flowTile(lines)),
+  });
+  const tile = tileToBBox(12, 935, 1686);
+  const west = tile.west + (tile.east - tile.west) * 0.2;
+  const { segments } = await source.fetchFlowDetail({
+    ...tile,
+    west,
+    east: tile.east - 1e-9,
+    south: tile.south + 1e-9,
+  });
+  assert.equal(segments.length, 4);
+  assert.ok(
+    segments.every((s) => s.coords.every(([lon]) => lon >= west - 1e-10)),
+  );
+  assert.deepEqual(
+    flowSegmentsToRoads(segments).map((road) => road.densityWeight ?? 1),
+    [1, 1, 0.5, 0.5],
+  );
+});
 test('bearing and distance reject nearby crossing and separate OSM roads', () => {
   const parallel = {
     ...main,