We should just really build rails. Self driving cars are dumping billions of dollars onto a problem better solved by rails. Several cities already have self driving trains including London, Singapore and Kuala Lumpar, and they transport millions of people every day without incident:
http://penguindreams.org/blog/self-driving-cars-will-not-sol...
Self driving car research is asinine. It won't even being to solve the transport problem in America and it's round-peg/square-hole tech. It has the cool factor but there are existing tech that are insanely more useful for a fraction of the cost. American hate public transportation (thanks GM) that we'll never see real/good transport implemented in America.