California drivers could soon see cars on the road driving themselves, courtesy of Google and the state government.

On Tuesday at Google's headquarters, the governor of California, Jerry Brown, signed into law a bill to legalize driverless cars. The bill had overwhelmingly passed the State Legislature. Google, which has been building the cars, says they are safer because they nearly eliminate human error. They could also be more fuel-efficient, the company says, and place California and the United States at the forefront of automobile innovation.

"It's significant because California is a big state, a first mover and really a big player," said Ryan Calo, a law professor at the University of Washington who studies autonomous vehicle law. "It's a good signal for the other states."

Technically, cars that drive themselves are not illegal, because there is no law that says cars must have drivers. The Google cars have been driving on California roads for a couple of years, including down Highway 1, a treacherous stretch overlooking the ocean. Some Google employees are now commuting to work in the cars.

But Google - along with other companies and research institutions developing such technology - wants to make the cars explicitly legal. Nevada and Florida have also legalized the cars.

"Because it's going to look strange to a sheriff driving by, and to remove uncertainty, what they want is a pronouncement that yes, it's O.K. to be driving cars around here without a driver," Mr. Calo said.

Google has been heavily lobbying lawmakers in California and elsewhere to support the cars. The California law gives Google and the people riding in the cars more freedom than other laws legalizing them. Nevada's law requires, for example, that the cars have a certain number of hours on the road and special license plates, while California's has few restrictions. The California bill indicated that lawmakers would add regulations later.

In addition to building the cars, which operate using computers, sensors and cameras, Google services like maps could be part of the cars. (Maybe that is why Google is dragging its feet on announcing a new maps app for the iPhone.) 

"I think Google's endgame is more about how they can be software as a service for the entire driverless car industry," Mr. Calo said.

In a statement on Tuesday, Google said, "Self-driving cars have the potential to significantly increase driving safety." The statement congratulated the Legislature "for building a thoughtful framework to enable safe, ongoing testing of the technology and to anticipate the needs and best interests of California citizens who may own vehicles with self-driving capabilities one day." 

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