I know this. I rode in one this week. I saw the car's human operator take his hands from the wheel and the computer assume control. "Autodriving," said a woman's voice, and just like that, the car was operating autonomously, changing lanes, obeying traffic lights, monitoring cyclists and pedestrians, making lefts. Even the way the car accelerated out of turns felt right.
It works so well that it is, as The New York Times' John Markoff put it, "boring." The implications, however, are breathtaking.