And what happens when a large event (e.g. a concert or game) ends, and thousands of people suddenly summon a Uber-type service? Will people, angry over long waits, get into brawls over Ubercars as they arrive? Will people be killed?
Of course, such events may well be banned as climate threats by then so it won't matter.
My thought is that the only way it will work is if the cars run fairly slowly, almost like a tram car ride. They may well be electric, running like little toy cars on an electric grid. It would require a repressive government to force people to accept a world in which they no longer drive cars but merely catch a ride on the robotic cars. I really don't see it happening anytime soon.