James Martin/CNET

On a nondescript street in downtown San Francisco, an unremarkable parking garage with dusty walls and painted-over windows seems like an abandoned warehouse.

Inside, however, it's a very different scene.

Row upon row of shiny self-driving cars await their moment. At first glance, they look like regular dark-gray Volvo SUVs and white Ford sedans. But they're decked out with rectangular sci-fi contraptions on their roofs. The Uber logo is emblazoned across their doors.

The garage is where the ride-hailing service houses a fleet of autonomous cars for San Francisco. The company hadn't said anything about when the self-driving cars would hit the road in California. But citing a person familiar with the launch, CNET reported on Tuesday that passengers in the city could expect to dial up one of these futuristic Uber cars "very soon."

On Wednesday, it became official. Uber said it has self-driving Volvo XC90 vehicles ready to go for people looking for a ride.

"Starting today, riders who request an UberX in San Francisco will be matched with a self-driving Uber if one is available," the company said in a blog post about the pilot program.

James Martin/CNET

Uber made its name by pairing passengers with drivers via a phone app. Over the past six years, it's grown from small startup to multinational company with operations in more than 400 cities in 72 countries. Now Uber is going a step further, venturing into robotics and artificial intelligence with autonomous vehicles. Some of its self-driving cars are already in service in Pennsylvania.

"We're at the very beginning stages of becoming a robotics company," Uber CEO Travis Kalanick said at the Vanity Fair Summit in San Francisco in October. "As we move toward the future, autonomy is a pretty critical thing for us. It's existential."

Uber's self-driving cars, accompanied by a human driver, have been traveling on the streets of San Francisco for the last three to four months. The company had said the cars were being used solely to collect data for maps. Mapping streets is part of readying autonomous vehicles for the open road, so they can identify routes and learn to detect obstacles.

The company declined to comment for this story. But earlier this week CNET learned that Uber would officially launch the program on Wednesday and that Uber had worked in partnership with Volvo to develop the self-driving cars.

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As of September, Uber didn't have a permit to run autonomous cars in California.

It may still lack that government blessing. On Tuesday, the DMV confirmed that Uber did not yet have the green light, meaning its road tests may be at odds with California's requirements for autonomous vehicles.

Uber addressed that issue in its announcement Wednesday, saying it doesn't believe it needs a testing permit.

"The rules apply to cars that can drive without someone controlling or monitoring them," Uber said. "For us, it's still early days and our cars are not yet ready to drive without a person monitoring them."

Until now, Uber's self-driving cars had been available in only one US city -- Pittsburgh. After 18 months of testing, the company launched a small fleet of autonomous vehicles in September in that city. Now when riders hail an Uber there, they have a chance of being picked up in a self-driving car that's accompanied by a "safety driver." Uber said it plans to have 100 self-driving cars in Pittsburgh by the end of the year.

Last week, Uber said it acquired New York-based artificial intelligence lab Geometric Intelligence and will soon launch its own Uber AI Labs. Geometric Intelligence's engineers reportedly specialize in machine learning and will help propel Uber's research in self-driving cars.

Interest and research in autonomous vehicles is a hot topic in the auto and tech industries. Automakers from Toyota to Ford to Volvo all have projects under way, and Silicon Valley giants like Google, Intel, Tesla Motors and Apple are also betting on the tech.

But self-driving cars could mean saying goodbye to drivers, who use their own cars to give Uber rides. While those drivers are important to the company's business model today, they have often caused headaches for Kalanick and his team. Some drivers have joined class-action lawsuits demanding to be classified as employees, rather than independent contractors, and other drivers have protested against the company, demanding better pay and support.

Uber has said it doesn't plan to phase out drivers anytime soon. But with the company launching a fleet of self-driving cars in San Francisco, that could change.

The scene down at Uber's garage is a busy one. A dozen Uber-branded autonomous vehicles line the street with their rooftop gear whirling away. Other self-driving cars, accompanied by a human or two, slowly roll in and out of the building.

Bahaddine, a full-time Uber driver not involved in the autonomous vehicle project who asked to be identified by just his first name, said Uber earlier told drivers about its plans to launch self-driving Fords and Volvos in San Francisco. He doesn't, however, think robot cars will take his job.

"I'm not worried," Bahaddine said. "It's only 100 cars coming."

First published December 13 at 11:02 a.m. PT.

Updated most recently on December 14 at 9:19 a.m. PT: Updates included new information on launch timing, Volvo's participation, the DMV perspective and Uber's official announcement.