How far can you walk in 15 minutes from each NYC borough hall?
Walking reachability from the five borough civic centers (City Hall, Brooklyn Borough Hall, Queens Borough Hall, Bronx County Courthouse, Staten Island Borough Hall), computed as 5, 10, and 15 minute walk isochrones on NYC's official LION street network and rendered as nested ring bands around each origin point. Measured, the contrast is not where you would guess. Four of the five 15-minute walksheds are nearly the same size: City Hall 2.75 km2 (most of the Financial District), Brooklyn 2.73, the Bronx 2.59, Queens 2.24. Staten Island is the outlier at 1.55 km2, 1.8x smaller than City Hall. The larger gap is street-network density: 15 minutes reaches 896 nodes from City Hall but only 339 from Staten Island Borough Hall. Each band carries area_km2 and node_count in its feature properties. The same open routing stack also produces bike and drive isochrones; this map isolates walking so the per-borough contrast stays legible.
Detrás del trabajo
Problema
Reachability comparisons across boroughs are usually eyeballed or produced with proprietary APIs. This uses only open city data and open-source routing.
Rol
I built the routing stack this analysis runs on.
Fuentes de datos
- NYC DCP LION street network (25d)
- NYC Geosupport for address search
- Traffic sources (NYC DOT volumes, TRANSCOM speeds) exist in the stack but were disabled for this run
Cadena de herramientas
Notas del proceso
Graph built from LION with per-mode edge costs, one-way restrictions, and grade-separated crossings. Reachable nodes computed with pgr_drivingDistance (Dijkstra) at 5, 10, and 15 minute cost limits, then polygonized with ST_ConcaveHull. Because independently built concave hulls do not automatically nest, bands were post-processed to cumulative unions (the 10 minute band includes the 5 minute band, and so on). For display, the cumulative bands are published as ring differences (each ring shows only its 5 minute increment) so the translucent fills do not overlap; properties stay cumulative (node_count and area_km2 mean within N minutes). Origin halls are included as point features. Concave hulls can slightly over-include narrow water crossings at band edges.
Validación
Strict band nesting (5 within 10 within 15) checked in PostGIS after the cumulative-union step: intersection coverage = 1.0 for all 10 adjacent-band pairs (5 origins x the 5-10 and 10-15 transitions). The published rings reassemble exactly to the cumulative walksheds (area difference 0.00 km2 per origin). Per-band reachable node counts and areas are included in feature properties.
Licencia de datos
LION is NYC Open Data (free and open)