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.

> I don't think individual vehicles can ever achieve the same envirnmental economies of scale as trains.

I think you'd be surprised. Look at the difference in cost per passenger mile.