I wonder if digitally linked convoys of cars and vehicles could replicate the smoother and quieter experience of trains, even on busy highways? The idea would be to use several "buffer cars" in front of the convoy of passenger busses. The entire convoy would be inter-linked and centrally controlled, so the "buffer cars" could accordion closer together and farther apart, so the passenger busses could use lighter braking acceleration. Build the busses with lots of sound damping and actively damped suspensions, and the experience could come close to that of a train.

The buffer cars would take up some additional highway area, but the passenger density of the convoy as a whole could still exceed private passenger cars.