you could reduce some aerodynamic drive by putting the cars end to end. essentially your car knows its destination and moves to the appropriate lane, the further you need to travel the more likely you end up in a far lane where cars are kept at a higher pace and closer together.

think of it as a modern version of Chicago highways where the left lanes get sectioned off on occasion with less chances to exit all to keep people in lanes consistently to reduce accidents from moving lane to lane.

fully autonomous cars and lanes dedicated to them and similar buses will remove the need for rail with in city limits beyond what exist. with no need to transfer vehicles and dedicated lanes you don't need as much planning for changes in travel patterns. fixed rail is always trapped, worse you end up with periods where you have too much capacity or too little and the inflexibility of track means no one else can use it. dedicate roadways can use the same space and be entirely flexible with easier maintenance and lower overall costs