FORTUNE -- The longtime dream of sci-fi fans-cars smart enough to drive themselves-is still many years off. That doesn't keep Google from trying. Its seven custom-equipped self-driving cars have logged more than 200,000 miles on the road without crashing. Well, one suffered a dent when a human driver rear-ended a Prius. So far the cars are officially legal only in Nevada-liability issues need to be worked out. More likely the technology will appear piecemeal in new vehicles. For instance, most car companies already offer accident-warning alarms.
Google says the sophisticated operating system that guides the cars makes them safer than if a human driver were behind the wheel. The vast majority of car accidents are caused by human error. Self-driving cars an also travel closer together, which would cut down on traffic congestion.