[kermit_de_fro]

Not so sure I agree. When I try to think of the core difference between subways and robotic vehicles, the only one I can think of is the relative lack of stops and the absence of cross-traffic.

With a serious and reliable driverless car system, stops could be integrated in a way which made them minimally impede traffic flow and the cross traffic optimized to maximize the flow over the whole road network.

Keep in mind we are talking about (in the limit at least) a network of driverless cars which can communicate. If traffic signals are in on the deal, I see no reason we shouldn't be able to do far, far better than a subway system.