With each passing year, the reality of sharing the road with fleets of self-driving, autonomous cars comes more and more into focus. Virtually every major automaker has made (or plans to make) substantial investments into the development of self-driving cars. But when will we see them?  When will they become so commonplace that people won’t think twice when they see one? Or better yet, won’t think twice about dialing up a self-driving Uber that arrives, on-demand, at their door step?