Well, Google is one step closer to making this a reality - by introducing it's new self-driven cars on the roads of America - developed by Stanford Professor and Vice President of Google - Sebastian Thrun. The vehicles have been licensed to legally drive on the highways of Nevada - the first of which is a Toyota Prius.
The cars themselves rely on a number of elements to ensure that they are safe - from radar sensors to a series of lasers, video cameras and also on a large database collected by real world drivers. So far, self driven cars have travelled on, amongst others, the Pacific Coast Highway and the Golden Gate Bridge.
With the prevalence, and the incredible detail being poured into Google Maps, self-driven cars were really only a matter of time. It will be quite interesting, from a safety point of view in the future to see how successful these cars are - especially in terms of the reaction time of a computer versus a human.