From what I understand, the autopilot can only be used on highways. I would suspect that highway travel is much safer per mile in the first place. Are we comparing highway driving with autopilot to regular mixed city/highway driving?
There's lots of highways in the US that are just 2 lanes, one in each direction, with a speed limit of 55mph and cross traffic from smaller roads that should stop first before turning on the highway in either direction. These are what we usually mean with the word 'highway'.