Oh I got a better idea. What if we link up the cars during long distance travel and have just one really powerful high efficiency car at the front pull all the other ones behind it and then every so often it reaches destinations where the other cars detach and go their own separate way.
Of course it will have dedicated routes, and probably specific times when the big car is passing by so there will be a schedule but that can be mitigated by running with a high frequency.
Heck we can even come up with a fun name for the last car in any Car Conga that essentially calls it a butt.