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

The goal is to "help prevent traffic accidents, free up people's time and reduce carbon emissions," project leader Sebastian Thrun wrote on Google's corporate blog.

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

It's not the first signal that Google wants to change how people get from place to place. In a speech Sept. 29 at the TechCrunch Disrupt conference, Google chief executive Eric Schmidt said: "Your car should drive itself. It just makes sense."

He added, "It's a bug that cars were invented before computers."

The cars have traveled a total of 140,000 miles on major California roads without much human intervention, according to Google's corporate blog.
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The cars know speed limits, traffic patterns and road maps, Thrun's posting says. They use video cameras, radar sensors and lasers to detect other cars.

Driving between Northern California and Southern California, the cars have navigated San Francisco's curvy Lombard Street, Los Angeles's Hollywood Boulevard and the Pacific Coast Highway, the blog says.

Google is pursuing many projects such as the cars that are unrelated to its core business, said Rob Enderle, principal analyst with the Enderle Group in San Jose.

"The word 'focus' is a word Google has never learned," he said, pointing to projects involving electricity distribution, vehicle design and artificial intelligence. He said cars that can drive themselves would allow commuters more time to surf the web, something Google would encourage.

- Associated Press