RadiusMapperDefinition
Drive-time polygon
Also known as: Drive-time isochrone, Driving isochrone, Travel-time polygon
A drive-time polygon is the geometric shape representing all locations reachable from an origin within a given driving time. It is the GIS term for a driving isochrone.
A drive-time polygon is the data structure (typically a GeoJSON polygon) that represents the boundary of a drive-time isochrone. GIS analysts, data scientists, and developers tend to use this term when they care about the polygon as data — for spatial joins, overlay analysis, or exporting to ArcGIS, QGIS, or Mapbox. Consumer-facing tools call the same thing a driving radius, drive-time map, or driving isochrone.
Key characteristics
- Typically exported as GeoJSON (Polygon or MultiPolygon).
- Can be intersected with demographics, competitor locations, or other spatial data.
- Changes with traffic conditions; static polygons reflect free-flow or average-traffic assumptions.
- Higher-resolution polygons are denser in vertex count near the origin and sparser farther out.
Common use cases
- Spatial analysis in ArcGIS / QGIS / PostGIS
- Programmatic API integration (site selection pipelines, logistics routing)
- Census and demographic overlay
- Map embeds on websites
Frequently asked about drive-time polygon
What format do drive-time polygons come in?
The standard format is GeoJSON — specifically a Polygon or MultiPolygon geometry. Some APIs also return Shapefile, KML, or a vector-tile layer. GeoJSON is the default because it's supported by every major mapping library (Mapbox, Leaflet, MapLibre, Google Maps) and every GIS tool (QGIS, ArcGIS, PostGIS).
How detailed is a drive-time polygon?
Most production isochrone APIs return polygons with 50-500 vertices, denser near the origin and sparser toward the outer edge. Higher-resolution polygons look smoother but cost more to compute and take more bandwidth to render. Many use cases (site selection, spatial joins) don't need high resolution — 50-vertex polygons are enough.
Can I use a drive-time polygon in PostGIS or ArcGIS?
Yes. Drive-time polygons returned as GeoJSON import directly into PostGIS (ST_GeomFromGeoJSON), ArcGIS (JSON to Features), and QGIS (drag-and-drop). From there you can do spatial joins with demographic data, calculate intersections with competitor locations, or dissolve polygons from multiple origins.
How do drive-time polygons handle traffic?
Traffic-aware polygons apply a time-of-day speed profile to each road segment. The same origin + time budget will return a smaller polygon during rush hour than at 3 AM. Most production APIs expose a 'departure time' parameter; without it they default to free-flow or average-traffic speeds.