(Bloomberg) -- Uber Technologies Inc.continues to dive head first into autonomous vehicles.Just don't call them that in California.

Starting Wednesday, Uber will let customers in San Francisco hopin a self-driving car, if they're lucky enough to hail one. There'sa lot the company won't say about the launch, like how many carsthey plan to roll out, but it will gradually introduce self-drivingVolvos in its hometown.

The seven-year-old startup doesn't have explicit permission fromthe CaliforniaDepartment of Motor Vehicles to test autonomous cars onthe road. The company has quietly had self-driving cars roaming thestreets of San Francisco for at least a few weeks without making itpublic, potentially violating the DMV's mandate. Uber said it hasshared its perspective that its cars don't qualify as autonomouswith the DMV.

The California DMV requires "autonomous" vehicle providers toregister with the state, something that Google, Mercedes-Benz,Nissan, GM's Cruise and Baidu have done. Companies are required tofile reports when drivers intercede or their cars crash. TeslaMotors doesn't file any such reports and similarly believes itdoesn't meet the requirements for autonomous vehicles.The DMV saidits permit process is designed to ensure public safety as thetechnology is tested.

"Twenty manufacturers have already obtained permits to testhundreds of cars on California roads. Uber should do the same," theagency said in an e-mailed statement.

Humans involved

While Uber executives use the words "self-driving" andclumsily trip over the word "autonomous," the definitions areup for debate, apparently. The DMV defines an autonomousvehicle as "technology that has the capability to drive avehicle without the active physical control or monitoring by ahuman operator." Uber's self-driving cars will have two humansinvolved, one ready to grab the wheel and another monitoring forpedestrians, directing the car to change lanes and helping recordincidents.

In one such ride-along Tuesday, a driver took control of thevehicle more than a dozen times in less than 30 minutes. Hisreasons included: He was worried that the car would gettoo close to a pedestrian, that the vehicle wouldn't let anothermerge and that the car would potentially create gridlock byentering an already crowded intersection. Other reasons were moremysterious.

Related: How self-driving cars will change the rules of theroad

Sometimes the car would simply hand over control to the driverwith little explanation. The driver said that the car wasprobably getting its sensors overloaded. In this one short jauntaround downtown San Francisco, when another car honked at theself-driving car for trying to change lanes, the Uber driver tookcontrol of the vehicle.

Definition of autonomous

The DMV has proposed updating its rules to clarify the definitionof autonomous. The new language would read, "Terms such as'self-driving', 'automated', 'auto-pilot', or other statements madethat are likely to induce a reasonably prudent person to believe avehicle is autonomous, as defined, constitute an advertisement thatthe vehicle is autonomous."

For now, at least, Uber is calling its cars self-driving. "Thepromise of self-driving is core to our mission of reliabletransportation, everywhere for everyone," Uber said in an emailedstatement. "While it won't happen overnight, self-driving will bean important part of the future."

In this photo taken Tuesday, Dec. 13, 2016, an Uberdriverless car heads out for a test drive in SanFrancisco. (AP Photo/Eric Risberg)

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