Not that this pulls us back to the topic at hand, but I find the idea that autonomous cars will happen first within cities as opposed to the lowest hanging fruit of the interstates somewhat upside down.
Consider me firmly among the skeptics of this entire technology.
On the front end, it is not at all clear as far as I can tell that the task being discussed is possible on a technical level. Driving feels sort of subliminal to people who drive because we're able to synthesize and act on information in a "human" way. But there isn't one program for how to deal with encroachments into the path of travel, missing lane markings, spontaneous detours, etc. So far we have easily defeated sensor suites and poor all-weather handling. I shouldn't say never, but I'm not going to discount the possibility that synthesis of all of these subroutines into "driving" is the sole purview of a "mind".
All of these things happen every day in cities and far less frequently on the open road--if the computers running these cars are dumb versions of us, we should dumb down the conditions under which they operate.
On the back end, let's say we figure it all out. We agree to some rules, we get cars that know all the rules, know when to break them as conditions change. Let's say it keeps literally all other things equal, except the ones that fans of self-driving cars point to: volume is up but congestion is down. I still think they'd be bad for city centers in the same way that cars are already. They still take up space whether they're moving or not, and they still reduce the friction that is the very substance of urbanity. The city is the opposite of hermetic, which is exactly what car manufacturers try to sell people: rooms on wheels.
One possibility is that they're coming, and soon, and we need to adapt to them. I guess there is some constituency for the politician who says, "as mayor, I would just sort of roll with things as they happen. You want parking? Here's parking. You want a charging dock for your pod? Sure."
Alternately, our planning for the future could say, "The heart of our cities is for people. We are going to move in that direction."
Sorry to rant, but long story short: don't think it'll happen, don't think it'll be good if it does.