The data

Close answers one question for every census block in the United States: how long does it take to reach the nearest amenity of each kind, on foot, by bike, and by public transit?

Census blocks

A census block is the smallest area the US Census Bureau publishes, usually a single city block in a town and a larger polygon in rural areas. There are about 8.5 million of them, each with a 15-digit GEOID. Close computes travel times from every block, so a block GEOID is the unit you work with: the origin of a summary, a row in an areal query, the centre of an isochrone.

What goes into a travel time

Travel times are routed from each block’s centre to the amenities around it. The pieces come from a few open datasets, and GET /v1/meta/vintage reports the live version of each:

Component	Source	What it provides
road_network	OpenStreetMap	streets and paths for walking and biking
transit_network	GTFS feeds	scheduled public-transit service
pois	Open points-of-interest data	the amenities themselves
blocks	2020 US Census	block boundaries and population
parks	OpenStreetMap parks	park access points, by size

Times are door to door, including the walk to a stop and any waiting for transit. Transit times assume a weekday departure around 8am and report a good-day (10th-percentile) trip; every isochrone reply echoes these assumptions, and GET /v1/isochrone/meta lists them without spending a token.

Two things that surprise people

Times are capped at 30 minutes. Close is about what is nearby: beyond half an hour, “how close is the nearest one” stops being the useful question. A time you read is always between 1 and 30 minutes.

A missing row means “not reachable within 30 minutes”, not zero. In an areal query, if a block has no row for grocery stores by walking, that block cannot walk to a grocery store inside the cap. This is the single most important rule for coverage analysis: absent is not the same as fast. When you count how many amenities a block can reach, the blocks with no rows for a category are the gaps.

Coverage and limits

• The data covers the United States.
• Times are computed from block centres, so a very large amenity (a park, a campus) is treated as a single point. Contour maps fill small interior holes for the same reason; see Isochrones.
• Each component has its own vintage. Check GET /v1/meta/vintage to see how current each one is, and GET /v1/last-updated for the newest publication time.
• Found a wrong or missing amenity? Report it from the close.city map so the correction reaches the next build.