One self-driving car fantasy is basically, "a taxi, but cheaper," the other one is "self-driving cars will solve traffic jams." If everyone's in a self-driving car that works great then safe distances between moving cars can be shorter and congestion caused by a cascade of drivers braking unnecessarily can be reduced. Like all self-driving car things I'm skeptical that any of this works as well as people imagine, but even if it does work you're going to increase capacity by... what.. 20%? I mean, great, cool, but that doesn't solve traffic jams. Can still only fit so many cars.
I admit I giggle when people in residential neighborhoods try to find ways to block outside traffic when Waze starts redirecting people through them. Not because I don't sympathize, but if I tried that in my urban residential neighborhood, the response would be "what do you expect, you live in a city?"
