WASHINGTON — Google Inc. is road-testing cars that steer, stop and start without a human driver, the company says.

The cars have traveled a total of 140,000 miles on major California roads without much human intervention, according to a posting 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 Sept. 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,” Schmidt said.

The Mountainview, Calif.-based technology giant has sent seven test cars a total of 1,000 miles without a human touching the controls at all, the New York Times reported.

The cars know speed limits, traffic patterns and road maps. They use video cameras, radar sensors and lasers to detect other cars, Thrun’s posting says.

Driving between Northern California 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.

The cars are never unmanned, Thrun wrote. He said a backup driver is always behind the wheel to monitor the software.