What I'm saying is even if that car was part of a network of attachable cars, the maintenance of the infrastructure needed to accomodate those cars is still way more expensive. This is not even getting into the discussion that if you have enough cars to need a highway (let alone enough to start attaching self-driving cars to each other), a train is more feasible. Period.

I will agree with you that the train is not the be all and end all. Good bike infrastructure (separated bike lanes that are connected through a planned network), light rail/trams and buses all have their place. What I disagree is the use of cars in urban and suburban centers/ corridors. There is no need. The only people that should use private vehicles are delivery vehicles, emergency vehicles, and those that live in impossibly remote areas that are very much disconnected from urban centers - areas that are hardly surrounded by a self-sustaining community.