The Mountain View company has tested seven robot cars without a human touching the controls. The cars are never unmanned. A backup driver is always behind the wheel to monitor the software.
The vehicles use video cameras, radar sensors and lasers to detect other cars. The cars know speed limits, traffic patterns and road maps.
The cars have traveled between Southern and Northern California and have navigated Hollywood Boulevard, San Francisco's curvy Lombard Street, and the cliff-hugging Pacific Coast Highway.
Google says the goal is to help prevent traffic accidents, free up people's time and reduce carbon emissions.
The Associated Press contributed to this story.
