There's got to be some way to transition to fully autonomous cars that could be implemented. I'd really like to see something that would put a hard limit of ~1

There's got to be some way to transition to fully autonomous cars that could be implemented. I'd really like to see something that would put a hard limit of ~15mph/25kmh on city streets for all motor vehicles. Upon entering a high-density zone, the car would automatically be put into a state with limits on speed, acceleration, horse power and adherence to traffic controls. People would still be behind the wheel but they would be severely restricted in how they operate within the high density zone. Basically this would make horseless carriages be conducted in a manner more similar to horse carriages.