The scale of a modern big city makes removing cars from it seem insane to me. It's not like you're propsing for cities to become all under one roof like the Burj Kalifah... Most people in a big city, miles wide, still have to meet clients and go get permits and attract customers from all over, etc. You can't just walk to them all and filling it up with enough trains & trollys above ground would look a lot like cars never left.

Maybe if Elon puts 50,000 tunnels under each of them with teslas driving thru them... Oh wait.