Isochronekart

Isochronekart, or isochrone map, is a map that delineates the geographic area reachable from a fixed origin within a specified travel time, using a chosen mode of transport and set conditions. The boundary lines enclose locations that can be reached within the time threshold, while points outside the boundary require more time. Isochrones are used to visualize accessibility and to define service areas for facilities, markets, or transportation networks.

Generation and data sources

Isochrone maps are typically produced with geographic information systems (GIS) and network analysis. They rely on a connected transport network (roads, sidewalks, transit lines) and data such as speeds, schedules, and travel times. For dynamic isochrones, real-time traffic, transit delays, or user-specified departure times can be incorporated. Algorithms compute the minimum travel time from the origin to all reachable network points, and the resulting set is converted into a polygon showing the area that can be reached within the threshold.

Applications

Common applications include urban planning and zoning, retail site selection, emergency response planning, and accessibility studies. They help compare how different modes (walking, driving, public transit) or times of day affect reachability, identify underserved neighborhoods, evaluate the catchment area of services, and optimize logistics and delivery routes.

Limitations and variants

Isochrone maps depend on data quality and assumptions about travel conditions and mode. Static isochrones assume fixed conditions, while dynamic isochrones attempt to reflect variability such as traffic or schedules. There are also variants that focus on specific factors (e.g., cost, energy usage) or that incorporate multi-modal transfers. Related concepts include travel-time analysis and service-area analysis.