I actually think that when autonomous cars are very safe, and all cars are autonomous, the next logical step is to improve the efficiency of transport. For example, if the cars are able to communicate with each other, we no longer need traffic lights. We could be buzzing by other cars going the other way at fairly high speeds without risk of collision. We could have smart spacing and merging to optimize traffic flows on highways. Speed limits for the vehicles might increase when inattentiveness and slow reaction times are out of the picture. And they would be dynamic based on changing conditions like # VRUs around, weather, day vs night, level of congestion, etc.