The problem I see is, if you still have to be fully attentive, supervising the computer and ready to take over, but not actually do anything... driving will be mind-numbingly boring. (That's assuming people are even capable of maintaining that attention, which many other comments address.) I mean, driving is usually already kind of boring, but at least the task keeps some part of your mind occupied. If the computer can take over completely - Google style - then you can do something else entirely. But this sounds like some kind of intermediate purgatory.