Google Inc is road-testing cars that steer, stop and start without a human driver, the company says. The cars have travelled a total of 225 300km on major California roads without much human intervention, according to a posting on Saturday on Google's corporate blog. The goal is to "help prevent traffic accidents, free-up people's time and reduce carbon emissions," project leader Sebastian Thrun wrote in the blog post. It's not the first signal that Google wants to change how people get from place to place. In a speech on September 29 before the Techcrunch "Disrupt" conference, Google CEO Eric Schmidt said "your car should drive itself. It just makes sense."It's a bug that cars were invented before computers."The New York Times published a report on the development on Sunday. The California-based technology giant has sent seven test cars a total of 1600km without a human touching the controls, the New York Times reported. The cars recognise speed limits, traffic patterns and road maps. They use video cameras, radar sensors and lasers to detect other cars, Thrun's posting explains. Driving between orthern and southern California, the cars have navigated San Francisco's Lombard Street, Los Angeles' Hollywood Boulevard and the Pacific Coast Highway, the blog says. Engineers consider the cars safer because they react more quickly than humans, the New York Times said. It said Google had not revealed how it hoped to profit from the research. The cars are never unmanned, Thrun wrote. A live driver is always behind the wheel to monitor the software. It says the technology is being developed by scientists who were involved in an earlier set of unmanned car races organised by the government's Defence Advance Research Projects Agency - the well-known Darpa drives.