General Motors, sometime before 2020, will put a car on the road that can drive itself. Well, almost, reports TOM KRISHER. Full autonomy could take 20 years.DETROIT, Michigan - General Motors, sometime before 2020, will put a car on the road that can almost drive itself.The automaker says the system, "Super Cruise," uses radar and a camera to steer a car and keep it between lane lines and radar to maintain a safe following distance and brake - to a stop, if necessary.GM and other automakers such as Mercedes, BMW and Lexus already offer radar-controlled autocruise that keeps a car a safe distance from other vehicles and perform an emergency stop even stop before a crash. They also have systems to tell a driver if the the car is lane-drifting but until recently engineers hadn't been able to steer with computers.STILL SOME BUGS John Capp, GM's director of electrical controls and active safety technology, said: "The steering control is the big additional piece."Engineers showed off system to the media at the company's testing ground in Michigan. The system adds control of electric power-steering to off-the shelf technology already available. Although they still have bugs to work out, a Cadillac SRX SUV equipped with the technology worked very well.Capp says a lot of development work is still needed for varying road conditions, sensor reaction, visibility of lane lines and how the system will interact with the driver, who would be in control and able to override the computer system. He says it's possible GM could sell the system well before 2020.The Cadillac brand would probably get it first, allowing a driver to release the steering-wheel on a freeway and let the car do all the work.YEARS TO GOCharles Green, an engineer who studies drivers' performance with the system, said: "GM is aware that the system could make drivers complacent, turning over control to the car even though the system isn't designed for that. So, before it gets to market, GM will have a feature that makes sure drivers are paying attention."The how is something that will become more apparent as we show Super Cruise in its later versions."Capp, however, said there were still many obstacles before cars could completely drive themselves. "Completely driverless cars are 20 to 30 years away."