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 form 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 New York Times published a report on the development earlier Sunday.

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 post says.

Driving between Northern California and Southern California, the cars have navigated San Francisco's Lombard Street, Los Angeles' Hollywood Blvd. 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 has not revealed how it hopes to profit from the research.

The cars are never unmanned, Thrun wrote. He said a backup 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 organized by the government's Defense Advance Research Projects Agency.