diff --git a/scripts/format-scope.json b/scripts/format-scope.json
index 9c4436652..6cfe9fe4e 100644
--- a/scripts/format-scope.json
+++ b/scripts/format-scope.json
@@ -873,5 +873,6 @@
   "src/tools/queries/aviation.test.mjs",
   "src/tools/queries/space.test.mjs",
   "src/tools/queries/media.test.mjs",
-  "src/tools/queries/places.test.mjs"
+  "src/tools/queries/places.test.mjs",
+  "src/layers/transit/source.test.mjs"
 ]
diff --git a/src/layers/transit/source.js b/src/layers/transit/source.js
index 6ccdb9e55..702b5ed00 100644
--- a/src/layers/transit/source.js
+++ b/src/layers/transit/source.js
@@ -5,6 +5,21 @@ export function createTransitSource({
   fetchImpl = (...args) => fetch(...args),
 } = {}) {
   return {
+    /** Read the public catalog of enabled feeds. */
+    async getFeeds({ signal } = {}) {
+      signal?.throwIfAborted();
+      const response = await fetchImpl('/api/transit/feeds', {
+        signal,
+        headers: { Accept: 'application/json' },
+      });
+      if (!response.ok)
+        throw new Error('Transit feeds HTTP ' + response.status);
+      const body = await response.json();
+      signal?.throwIfAborted();
+      if (!Array.isArray(body?.feeds))
+        throw new Error('Malformed transit feed catalog');
+      return body.feeds;
+    },
     getHistory(feedId, vehicleId, { signal } = {}) {
       signal?.throwIfAborted();
       return fetchTransitHistory(feedId, vehicleId, signal, fetchImpl);
diff --git a/src/layers/transit/source.test.mjs b/src/layers/transit/source.test.mjs
new file mode 100644
index 000000000..88d66664a
--- /dev/null
+++ b/src/layers/transit/source.test.mjs
@@ -0,0 +1,46 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { createTransitSource } from './source.js';
+
+const json = (body, status = 200) =>
+  new Response(JSON.stringify(body), {
+    status,
+    headers: { 'Content-Type': 'application/json' },
+  });
+
+test('the feed catalog is read from the public catalog route', async () => {
+  const requested = [];
+  const feeds = [
+    {
+      id: 'mbta',
+      name: 'MBTA',
+      center: { lat: 42.36, lon: -71.06 },
+      loadRadiusKm: 60,
+    },
+  ];
+  const source = createTransitSource({
+    fetchImpl: async (url) => {
+      requested.push(url);
+      return json({ feeds });
+    },
+  });
+  assert.deepEqual(await source.getFeeds(), feeds);
+  assert.deepEqual(requested, ['/api/transit/feeds']);
+});
+
+test('feed catalog failures are reported', async () => {
+  const failing = createTransitSource({ fetchImpl: async () => json({}, 503) });
+  await assert.rejects(failing.getFeeds(), /Transit feeds HTTP 503/);
+  const malformed = createTransitSource({
+    fetchImpl: async () => json({ feeds: {} }),
+  });
+  await assert.rejects(malformed.getFeeds(), /Malformed transit feed catalog/);
+  const aborted = new AbortController();
+  aborted.abort();
+  await assert.rejects(
+    createTransitSource({
+      fetchImpl: async () => json({ feeds: [] }),
+    }).getFeeds({ signal: aborted.signal }),
+    (error) => error.name === 'AbortError',
+  );
+});