Waymo’s driverless cars are classified as SAE Level 4, not Level 5, because they operate autonomously only within defined conditions. This distinction matters because a vehicle can complete journeys without a human driver yet still be limited by geography, road types or weather, whereas Level 5 would need to drive anywhere a human could.

The SAE framework has six levels, from Level 0 to Level 5: Levels 1 and 2 assist a human driver, while Level 3 can take control temporarily but may require takeover. At Level 4, occupants are passengers when the system operates within its operational design domain; Level 5 has no such domain restrictions. Waymo’s sixth-generation Driver may cope with more varied environments, including severe winter weather, but expanding those boundaries still leaves it at Level 4.