Uber launches self-driving car fleet in San Francisco, faces DMV backlash
A pilot model of an Uber self-driving car goes down a street in Pittsburgh, Pennsylvania. (AFP /Angelo Merendino)

Uber has rolled out its self-driving car fleet in its hometown of San Francisco, despite lacking the proper permit that state regulators say is required.

Starting Wednesday, riders who request an UberX, one of the company's budget ride options, may be matched with a self-driving Uber. It is unclear how many of these cars Uber has in San Francisco.

Launching the program kicked off a battle with the California Department of Motor Vehicles, which said on Tuesday that Uber does not have a permit to test autonomous vehicles on California roads, and demanded the company follow the permitting process that is in place.

"Twenty manufacturers have already obtained permits to test hundreds of cars on California roads. Uber shall do the same," the agency said in a written statement.

Uber's self-driving cars have been seen around San Francisco since at least September.

Uber argues that its cars are not able to drive without a person monitoring them - a driver and an engineer are in the front seats to take over frequently in situations such as a construction zone or pedestrian crossing - so the California law does not apply. California defines autonomous vehicles as cars that have the "capability" to drive "without the active physical control or monitoring of a natural person."

"All of our vehicles are compliant with applicable federal and state laws," a spokeswoman said.

In a company blog post, Uber called on California to take a more "pro-technology" approach to regulating autonomous cars.

"Several cities and states have recognized that complex rules and requirements could have the unintended consequence of slowing innovation," Uber said. "Our hope is that California, our home state and a leader in much of the world's dynamism, will take a similar view."

Uber said the San Francisco program will mimic its pilot in Pittsburgh, Pennsylvania, where three months ago Uber unveiled its secretive work on autonomous cars for the first time to the public. The company started with just four self-driving cars available to Pittsburgh passengers, although it had a fleet of more than a dozen for testing.

At that time, engineers at Uber's Advanced Technologies Center in Pittsburgh, where much of the company's research on autonomous cars takes place, emphasized that Uber was not attempting to build a driver assistance system. Rather, Uber had its sights on building fully autonomous cars, with no driver intervention.

Uber's San Francisco fleet features the Volvo XC90, an upgraded model from the Ford Fusions that were unveiled in Pittsburgh.

(Editing by Alistair Bell)