Isn't a vehicle that goes from anywhere to anywhere on your own schedule, safely, privately, cleanly, and without billions in subsidies better?

I don't think individual vehicles can ever achieve the same envirnmental economies of scale as trains. Certainly they're far more convenient (especially for short-haul journeys) but I also think they're somewhat alienating, in that they're engineering humans out of the loop completely which contributes to social atomization.

Trains only require subsidies in a world where human & robot cars are subsidized.

As soon as a mode of transport actually has to compete in a market for scarce & valuable land to operate on, trains and other forms of transit (publicly or privately owned) win every time.

Cars don't work in dense places.

Not necessarily, and your premise is incorrect.

Billions of subsidies? Im confused you talking about cars or trains.

>without billions in subsidies

Is there a magic road wand?