Well, why don't we go a step further then and physically connect the vehicles? Maybe we can also make them longer and fit more passengers? And we could optimize the rolling friction, replace rubber on tarmac with something better like steel on steel, and use some sort of tracks to provide the sideways forces?

You jest, but I'd love it if we could automatically group cars into physically connected trains for long distance travel, and have them automatically split off when they approach their destination. Maybe there's some way to do that with rails, carrying peoples' cars, but not sure if the efficiency gain is worth the increased complexity of including another set of wheels/motors/etc, and making the automated separation/joining work with all of that.

Are the other passengers quiet and housebroken? Does the steel track go to my office? (Broken or misused rail switches cause a lot of accidents.)