15 minutes, but for whom?

A free, public-good civic map. The usual "15-minute city" map assumes a fit adult. This one shows how far a child, a pregnant woman, an elderly person and a newcomer can actually walk in 5, 10 and 15 minutes from a point you click, and how heat, rain, slopes and broken lifts change that.

First area: BGC, Taguig (Metro Manila). Live at https://fifteen-for-whom.vercel.app.

Inspired by Francesco Procacci's map (Python workflow) shared by Milan Janosov.

Run it

npm install
npm run dev       # local dev server
npm run lint      # tsc --noEmit + eslint
npm run build     # static site into dist/
npm run smoke     # checks dist/: link-preview tags, PNG, MP4 (H.264, < 5 MB), graph
scripts/check-live.sh https://fifteen-for-whom.vercel.app   # same checks against a deployment

No API keys, no paid services. Everything runs in the browser; the street graph is a committed static file (public/data/bgc.json, ~330 kB, ~90 kB gzipped).

Method

1. Graph. scripts/build-graph.mjs downloads every highway=* way in the area's bounding box from the Overpass API, drops what pedestrians cannot use (motorways, trunk roads, busways, cycleways, foot=no, private/permit access) and splits ways at shared nodes into edges. Each edge stores its length, its geometry and flags: steps, footbridge, covered, major road, grade.
2. Cost per edge (src/engine.ts, edgeCosts): time = length / (speed × multipliers), where the multipliers depend on the persona and the toggled conditions (below). Edges can be blocked.
3. Isochrone. Dijkstra from the street vertex nearest the click (within 250 m), on the client. A piece of street counts as reached in N minutes if the walker arrives at one end with time left; partial edges are cut at the exact distance. The map draws the reachable streets for 5, 10 and 15 minutes (opacity falls with time) and each persona gets its own colour and a small line offset so overlaps stay readable.
4. Reading the numbers. The sidebar shows each persona's 15-minute reach as a percentage of the street length a fit adult (1.33 m/s, dry, flat, nothing blocked) reaches from the same point.

Personas (defaults, all in PERSONAS in src/engine.ts)

Persona	Speed	Extra
Fit adult (reference, not drawn)	1.33 m/s
Child	1.0 m/s	Heat sensitivity ×1.2; needs lifts (strollers/small children on stairs)
Pregnant woman	1.1 m/s	Heat ×1.4, slope ×1.3; needs lifts
Elderly person	0.9 m/s	Heat ×1.5, slope ×1.5; needs lifts
Newcomer	1.33 m/s × 0.85	Wayfinding penalty: 15% slower plus 8 s at every junction with 3 or more ways

All of these numbers are assumptions. They are rounded, plausible values chosen by the author, they are population averages rather than individual limits, and none is backed by a source with a verified URL. Earlier drafts named papers from memory; those citations were removed because they were not verified. Treat the figures as illustrative and change them in PERSONAS if you have better data.

The slope penalty uses Tobler's hiking function (Tobler 1993, NCGIA Technical Report 93-1), applied to urban walking as an assumption; see Limitations.

Conditions

Toggle	Effect
Heat	Speed × (1 − 0.18 × heat sensitivity) on uncovered edges, × (1 − 0.06 × sensitivity) on covered ones
Rain	Speed × 0.85 on uncovered edges, unchanged on covered ones
…avoid uncovered	Extra ×0.55 on uncovered edges (stand-in for detouring to stay dry)
Slopes	Tobler's function, speed ∝ exp(−3.5·|grade + 0.05|), relative to flat, with persona slope sensitivity multiplying the grade
Broken lifts	Steps and footbridges are blocked for personas that need lifts (child with stroller, pregnant, elderly). The newcomer is unaffected.

Steps are always slow (×0.5 speed) for everyone, even with lifts working.

Data sources

• Streets, steps, bridges, covered, incline: © OpenStreetMap contributors, ODbL, via the Overpass API (overpass.kumi.systems, overpass-api.de). The committed extract records the OSM timestamp.
• Base map: OpenFreeMap (free, no key), © OpenMapTiles, data © OpenStreetMap contributors.
• No elevation data is used (see limitations).

Limitations (please read)

• Slopes are a placeholder. No DEM is bundled. Only OSM incline tags are used; where a bridge, flyover or tunnel has none, a 5% ramp of unknown direction is assumed and penalised both ways. BGC is nearly flat, so the slope toggle changes the result only slightly. A real DEM (e.g. Copernicus/SRTM sampled at build time) is the obvious next step.
• Covered walkways are under-mapped in OSM. Only covered=yes, indoor=yes, corridors and tunnels/building passages count as covered. BGC has many covered walks and mall connections that are not tagged, so heat and rain effects are probably overstated.
• Lifts and escalators. OSM has no status for broken lifts. The toggle is a what-if: all steps and footbridges are blocked for the personas that need lifts. Lifts that exist are not modelled individually.
• Crossings and traffic. Crossing waits, signals and unsafe crossings are not modelled. Streets with sidewalk=no are still walkable.
• Private estates. Paths with private or permit-only access are excluded; open malls and plazas may be missing or present depending on tagging.
• Personas are averages. Real people vary far more than these four numbers.
• The coverage box is small; clicks near the edge see a truncated network.
• Not tested on real devices or in a real browser in this build, only type-checked, built and smoke-tested; the engine was exercised on the real data in Node.

Link preview

public/og/preview.mp4 (1200×630, H.264, ~0.3 MB, 7 s) shows the isochrones growing for each persona. public/og/preview.png is the 1200×630 fallback and public/og/player.html is the twitter:player page. Regenerate all three after changing the engine or graph:

npm run preview-video   # needs ffmpeg; renders frames with @napi-rs/canvas

The head tags in index.html use absolute https://fifteen-for-whom.vercel.app URLs; update them if the domain changes.

Add a new area

1. Add an entry to src/areas.json:

   "komoro": {
     "name": "Komoro, Nagano",
     "center": [138.4267, 36.3275],
     "zoom": 15,
     "bbox": [138.41, 36.315, 138.445, 36.34],
     "graph": "/data/komoro.json",
     "start": [138.4267, 36.3275]
   }
   

   (bbox is [west, south, east, north]; keep it small, about 2 km × 2.5 km, to stay fast.)
2. node scripts/build-graph.mjs komoro (add --refresh to re-download from Overpass; raw output is cached in the gitignored data/raw/).
3. Commit public/data/komoro.json. Open the site with ?area=komoro.
4. Tune the persona or condition constants in src/engine.ts if local conditions (e.g. snow) need different assumptions.

Support

Free to use. A Donate link appears in the footer once DONATE_URL in src/config.ts is set (empty by default).

License

MIT, see LICENSE. Map data © OpenStreetMap contributors (ODbL).

Browser tests

npm run e2e installs Chromium and runs Playwright (e2e/app.spec.ts) against the built site with software WebGL. It checks that tiles render, that a click draws 5/10/15 min rings for all four personas, that each toggle changes the geometry, and that the layout holds at 390px. npm run smoke runs the tag checks and then this, so CI covers both. Screenshots from the last run are in docs/screenshots/.