"A decade hence, we might find ourselves even more beholden to automotive infrastructure, as city streets swell with the dread “zero-occupancy” vehicles—empty cars roaming about running errands for their affluent owners. And those left behind by the first car revolution—those whose paychecks are already consumed by automotive expenses or who rely on increasingly shaky public transit networks—will be even more hopelessly marooned in the mobility deserts that remain." [0]
I'm growing more concerned that self-driving cars will actually increase traffic. There is an equilibrium found based on a driver's willingness to drive. Once we eliminate that need for a driver, that equilibrium disappears.
For example, if I have a sudden urge for ice cream and I see that my freezer is empty, I have to make a decision whether it's worth driving all the way to the grocery store just to buy a single item. Suppose I decide, no.. it's not worth the hassle.
Now introduce an app that allows me to send an autonomous car to the store, have the employee fulfill my order, and the car brings back my ice cream. What you'll have is a horrible gridlock of people using these cars to buy single items at a time, out of impulse. Before, the hassle of me having to drive to the store stifled that impulse. Without having to drive to get the items I want, I no longer have stake in that matter. Who cares if traffic has gotten worse? I'm not in it.
[Edit - add another scenario:] Consider another scenario. My friend wants to borrow an item X from me. He doesn't need it immediately, so I may decide to drop it off at his house next week when I drive over to visit. Now with a self-driving car, heck... why not just send the item X over to him now? It's no hassle to me since I don't have to drive, and he gets it sooner. But now I've just placed more burden on our roads and our environment.
This also spells a bad scenario for climate change, if it increases the amount of vehicle-miles traveled and CO2 emissions.
While it's possible for autonomous vehicles to reduce sprawl by eliminating vast parking lots and road space, I think a more plausible scenario is that people use self-driving cars as their own personal butler, picking up items here and there from stores, increasing the strain on our roads. After all, if you had an app on your phone that allowed you to order a vehicle to pick up items from a store, all in the comfort of your own home, wouldn't you make a butler out of this car?
[Edit] Perhaps what self-driving cars will enable is a plethora of what amounts to useless and wasteful voyages.
[0] http://www.politico.com/magazine/story/2017/06/30/biggest-ch... (the section titled "Self-driving cars")