The map is a memory
A robotaxi does not discover the road fresh each time. Before a service opens in a city, mapping vehicles drive every street and build a high-definition map: lane boundaries, curbs, crosswalks, signal positions, speed limits and the exact geometry of intersections, accurate to a few centimetres. On the road, the car matches what its sensors see against the map to work out precisely where it is, and reads the map to know what is coming before its sensors can see it.
The geofence
The mapped area is the service area, and its boundary is the geofence. Rides start and end inside it, and the car will not route beyond it. Geofences grow as maps and permits expand: Waymo's Phoenix area went from a few suburbs in 2018 to hundreds of square miles, and its San Francisco service expanded down the Peninsula over 2024 and 2025. When a company says it is "launching" in a new city, a new geofence is usually what it means.
The operational design domain
The geofence is one dimension of a larger idea, the operational design domain: every condition under which the system is designed to operate. Geography, road types, speed range, weather, time of day, even the kinds of events it is built to handle. A Level 4 system is only automated inside its ODD. Heavy rain, freeway driving and airport pickups have each been outside a service's domain before being added after testing.
Driving without a map
Building and maintaining HD maps is expensive, and a map is wrong the moment a road is repaved. Some developers, Tesla and Wayve among them, aim to drive with only standard navigation maps and rely on perception for the rest, which would let them operate anywhere at once. Mapped operators reply that a map is simply more information, and that they also handle unmapped changes when they must. Both approaches are on the road; the question is which scales safely.
Frequently asked questions
Why can't a Waymo take me outside the service area?
Because the car only operates on roads it has mapped and its operator has approved, and it has no driver to fall back on outside them. The service area is the boundary of its operational design domain.