We definitely need at least four train tracks for mass transit to work. Two tracks each way: one express and one local. What I don't understand is why do auton

We definitely need at least four train tracks for mass transit to work. Two tracks each way: one express and one local. What I don't understand is why do autonomous self driving cars and subways have to be either or. Why can't we do both? After all, we can't use the subway for ambulances and fire trucks so we still need to build some kind of roads even if we had full confidence in the subways... Just thinking out loud... Unless we had helicopters for emergencies? Can we have a town with no paved road? Only sidewalks? That's still paved, right? Can trash collection also take the subway?