Photo: Paul Chinn, The Chronicle

Waymo, the self-driving unit of Google parent Alphabet, this week applied to test cars without drivers on California roads, The Chronicle has learned — even as a pair of recent crashes has heightened fears about the safety of autonomous vehicles.

Waymo confirmed Friday that it had submitted an application to the California Department of Motor Vehicles to test cars without a backup driver behind the wheel. So far, only two companies have applied for such permits, and the other company’s identity has not been publicly revealed.

According to a source familiar with the matter, Waymo plans to start testing near its Mountain View headquarters, an area where its fleet of self-driving Chrysler Pacifica minivans have already logged many miles with backup drivers. Over time, the company will expand testing of autonomous cars with no backup driver to more of the Bay Area, the source said.

Waymo’s approach will be to extensively map a terrain by having vehicles with test drivers cover it first, before using no-driver cars.

The move comes less than a month after a fatal accident involving a self-driving Uber SUV in Arizona raised fresh concerns about the safety of autonomous cars. That vehicle had a backup driver behind the wheel when it struck and killed a pedestrian on March 19, but dashcam videos showed the driver was not watching the road.

Days later, a Tesla Model X operating in Autopilot mode slammed into a concrete freeway divider near Mountain View, killing the driver. Although Autopilot, which requires the driver to pay attention, does not represent full self-driving technology, it is considered a major step in that direction.

Waymo CEO John Krafcik said that the Arizona tragedy would not have happened with a Waymo car.

“We have a lot of confidence that our technology would be robust and would be able to handle situations like that one,” Krafcik told a car dealers group the week after the accident.

There’s a certain poetic justice in Waymo being an early applicant for California’s no-driver car permits.

The company started testing autonomous vehicles in 2009, when the idea was considered as futuristic as personal jetpacks. It was the third company to receive a permit for road tests — with backup drivers behind the wheel — in California. Its cars have driven themselves some 5 million miles, 2 million of them in California.

Waymo’s success in getting cars to drive themselves has spurred major automakers, tech companies and startups to pursue the same goal in what is now a worldwide, multibillion-dollar race.

Waymo at one point designed a bubble-shaped autonomous car that had no steering wheel or brake pedal, but California officials would not allow it onto public roads until those features had been added. Under the new permit program to which Waymo applied this week, California now can approve cars without manual controls, although Waymo’s existing autonomous fleet all have controls allowing a human driver to take the wheel.

The DMV confirmed that it has now received applications from two companies for no-driver testing, which became legal in the state on April 2. The department has not identified either company.

The first company to apply submitted an application in early April, the DMV said. The department notified that company on Thursday that its application was incomplete and asked for more information.

The DMV has 10 days after applications are submitted to say if they are complete and an indefinite timeline to approve or deny requests.

The DMV requires the companies applying for permits to notify specific cities where they plan to operate and submit a law enforcement interaction plan to local police departments. Representatives of some cities that received the notices said they were excited to welcome Waymo’s no-driver cars. All of those cities have already been sites for Waymo’s autonomous testing with backup drivers.

Autonomous vehicle technology “is going to be crucial in helping the Silicon Valley reach its safety and transportation goals,” said Los Altos Councilwoman Jeannie Bruins.

“Waymo has done extensive vehicle testing on our local streets with a good safety record,” Mountain View City Manager Dan Rich, said in a statement. He commended the company for committing to “transparency and information sharing.”

In Sunnyvale, Mayor Glenn Hendricks likewise said he looks forward to working with Waymo.

However, some autonomous-car experts questioned whether it’s premature to unleash no-driver cars, especially in light of the recent Uber and Tesla crashes. Both incidents are still under investigation.

“Ultimately it is not Krafcik’s confidence in AV readiness that should matter; it should be the DMV’s confidence, based on objective data, studies, and verifiable tests,” said Benicia lawyer Jim McPherson, who runs the SafeSelfDrive consultancy, in an email. The DMV has followed traditional U.S. policy of ceding vehicle-safety concerns to federal regulators, who in turn have deferred them back to developers, again in line with long-standing policy.

One source of objective data is the DMV’s required disengagement reports, which show how often a company’s backup drivers need to take control of their self-driving vehicles during tests. Waymo’s report for 2017 showed that happened, on average, once every 5,600 miles. (By contrast, Uber struggles to achieve a disengagement rate of once every 13 miles, the New York Times reported.)

“If that rate still holds today, and if Waymo deploys 100 cars that drive 50 miles per day, then there will be an average of one disengagement somewhere in Mountain View every day,” McPherson wrote. “Let’s all hope no one gets hurt.”

Each company that applies for a permit must specify where and under what conditions the no-driver cars can operate.

Waymo told the DMV its cars can handle city streets as well as highways up to 65 mph, and can navigate both day and night, through fog and light rain. The implication is that the cars are not yet ready for snow or torrential downpours.

Under California rules, cars without drivers must be able to communicate with remote operators who can intervene in case the cars get confused by obstacles such as road construction.

Sources said that Waymo does not plan on operating its cars remotely — even in difficult situations — but it will remotely monitor them during tests. If one of the cars encounters something it doesn’t understand, such as complicated road construction, the car will contact Waymo for help recognizing the situation. After human testers give it feedback, the car will then decide how to navigate the situation.

Waymo has been doing public road tests of no-driver cars in Arizona since October 2017, starting in Phoenix but with plans to expand. It has announced plans to start a driverless taxi service in Arizona this year.

While the company has not said anything about offering robot taxis in the Bay Area, sources said it is likely to follow a similar evolution here as in Arizona.

Waymo has done extensive no-driver tests in California at Castle, a a former military base in Merced County. Because it is a private test track, Castle is not subject to the same rules as public roads.

Carolyn Said is a San Francisco Chronicle staff writer. Email: csaid@sfchronicle.com Twitter: @csaid