>Once cars are fully autonomous and become cheaper, faster, and more efficient than current forms of public transportation You state this as if it is inevitabl

>Once cars are fully autonomous and become cheaper, faster, and more efficient than current forms of public transportation You state this as if it is inevitable, but I don't see this as true. Take, for example, the density in cities in, say, China. If we took everyone who took the buses and the subway trains and moved them out to cars today, Shanghai would be a perpetual traffic jam. In addition, you have pedestrians to deal with at surface level, which of course will slow cars down. The laws of physics also dictate that things must slow down during things like turns, and when you exit the tunnel. Unless we create dedicated interchanges and acceleration and deceleration lanes... That already exists and it's called a highway. Traffic is rarely made slow on the highway because of the cars traveling on it or the number of lanes, it's made slow by the cars wanting to get off and slowing down. Yes, you can make the cars move faster, but the bottleneck is precisely where the cars decelerate, even today. I fail to see how making a bunch of tunnels solves the issue.