"the real potential of these cars is we have a transportation system that is much better on the environment because it allows more people to use vehicles in a very different way,"

"One of the big potentials is that it changes the urban landscape because you can have your car drive to where you are and pick you up, as opposed to needing to park your car within a mile of where you are at,” Tucker says.

Since these cars would be able to communicate with each other, there would effectively be less traffic and congestion. Also, drivers wouldn't have to worry about parking.

http://www.businessinsider.com/get-ready-for-self-driving-cars-that...

Since you don't own the car yourself, all of the excess energy left in the car's battery could be used by someone else, and not just go to waste. So the entire system ends up using less energy than a bunch of individually driven cars. 

these forecasts are not concrete predictions, but merely a tool for thinking about how cutting edge technology might affect the future constructively