I think people like their privacy too much for that, as efficient as it may be. It seems more likely to me that private (or public single-occupant) autonomous cars will become smaller. Something like a Smart car size autonomous EV -- small enough to minimize costs, large enough to be useful for the single rider.

A developed country is not a place where the poor have cars. It’s where the rich use public transport — paraphrased from Enrique Penalosa, former Mayor of Bogotá, Colombia

http://newyork.thecityatlas.org/lifestyle/developed-area-ric...

I think privacy is something that is a function of cost benefit. When road pricing becomes ubiquitous (as it will given the march towards EV), people will begin shift to public transport.

Perhaps the solution for Americans will need to be different to that of the rest of the world.

Prepare to be surprised

There are already congestion charging schemes. I doubt it will ever get to a ban (and you can wouldn't want that) but I think it will be expensive. You could actually just charge a flat fee for road space, so a bus carrying 70 people is 3 times as long as a car, so only pays 3 times more. And maybe a separate charge of minimum standard to discourage nitrogen or particulate air pollution.

I suspect that the move to EV will eventually create a revenue hole from reduced fuel taxes necessitating the move to road pricing. Politically unpalatable but I think a necessary step.