Maybe 'when will cars drive themselves?' is the wrong question
Driving must be easy, because so many people do it while talking on or looking at cellphones. Pardon the snark, but if driving really WAS that easy, machines would already be able to take over for humans, with no flaws.
We're still not there; self-driving cars show promise, but Peter Norton is convinced it's going to take a very long time to convey all the nuances of operating motor vehicles into computer programs.
Norton explains his concern and expands upon it, in the book Autonorama: The Illusory Promise of High-Tech Driving. He visits to talk about how to move ALL of us--in motor vehicles and not--into the future.