If we had truly autonomous cars, we wouldn't need a car per person. One car can take you to your park-and-ride, your wife to work, your son to middle school, and your daughter to elementary school an hour later. Then, it can pick each person up and take them home. And just in case scheduling conflicts, you can team up with your brother and sister to form a 3-car system. Team up with more people, and you can start carpooling and sending the nearest available car to whoever needs it like a taxi service. Get a city involved, and you'll have the more adaptive and cheap bus system in the world, that picks you up on your doorstep and transfers you from car to bus with perfect timing. Routes and transfer points will change dynamically to route traffic most efficiently. Bus-only lanes and traffic light control will ensure calculations are accurate for the majority of the route. Even if you drove like a maniac, you'd have trouble beating an autonomous system that synchs all the traffic lights to its benefit, drove speed limit on the bus-only lane, and does a perfect transfer to car to take you from doorstep to doorstep. Or maybe it wouldn't be that hard because there will be so few cars on the road that owning a car would be like having your own private Jet.