Everybody you replied to you made a completely different hypothesis but the waymo head itself mentioned why they waited on highways: on regular roads, if the computer fails to maneuver, you have an extremely simple, generally safe temporary solution: you just stop the car. Stopping a car is always kinda acceptable in regular roads. Its not an acceptable solution to undefined problems in the highway. This becomes important because in a Tesla theres still a requirement for a driver to be there to take care of worst case scenarios but in a waymo thats not true.