Two officers in San Bruno, Calif., a suburb of San Francisco, were checking for drunken drivers over the weekend when they saw a car make an illegal U-turn right in front of them. But it wasn’t a drunken driver. It was a driverless Waymo taxi.
The officers turned on the flashing lights on their police car and pulled behind the Waymo, which automatically came to a stop. But the officers could do little else other than tell a Waymo representative what had happened.
“Since there was no human driver, a ticket couldn’t be issued,” the San Bruno Police said in a statement on Facebook that included a photo of an officer peering into the empty driver’s seat of the taxi. “(Our citation books don’t have a box for ‘robot’).”
The bizarre traffic stop pointed to the challenge law enforcement officials face in trying to ticket autonomous vehicles for moving violations that would be routine if a human driver were behind the wheel.
Last year, Gov. Gavin Newsom of California signed a law authorizing the police to issue “notices of autonomous vehicle noncompliance” when they see driverless cars breaking local traffic laws. But the law did not specify any penalties associated with those notices and it does not take effect until July 1, 2026.
Until then, there are no clear rules in California governing how to enforce local traffic laws for autonomous vehicles, said Sgt. Scott Smithmatungol of the San Bruno Police Department’s Traffic Division. Enforcement “feels like it’s still in the beta-testing stage,” he said.
Waymo said in a statement that its autonomous driving system, known as the Waymo Driver, was “designed to respect the rules of the road.” After reviewing the traffic stop in San Bruno, the company said it took “immediate steps to address this” and was “committed to improving road safety through our ongoing learnings and experience.”
Sergeant Smithmatungol said it was early Saturday morning, just after midnight, when he and another officer saw the Waymo make the illegal U-turn from a left-turn-only lane, right next to a posted no U-turn sign. Sergeant Smithmatungol and his partner drove behind the Waymo with their vehicle’s lights flashing, and the taxi stopped. (The vehicles, Waymo says, are designed to pull over in a safe place when they detect police lights and sirens).
Sergeant Smithmatungol’s partner approached the vehicle and looked inside. “Oh, no one’s in it,” he said.
The officers, relying on their training from Waymo, used the taxi’s two-way communication system to contact a Waymo representative, who thanked them for reporting the illegal U-turn, Sergeant Smithmatungol said. Then the officers drove off, leaving the Waymo behind.
“Hopefully the reprogramming will keep it from making any more illegal moves,” the San Bruno Police said in their statement.
Unlike California, Arizona has a state law that allows the police to issue traffic citations to driverless vehicles, just as they would to regular drivers.
But Sgt. Brian Bower, a spokesman for the Police Department in Phoenix, where Waymo has been offering fully driverless taxi service since 2020, said he had not heard of any officers actually issuing such tickets.
He said there had been very few issues with Waymo taxis in the city, although some have had trouble detecting yellow caution tape. When the vehicles have been involved in accidents, he said, human drivers have been at fault.
Still, Sergeant Bower said Arizona’s law was a good thing. “It puts autonomous vehicles at the same standard as we put our citizens, and that’s a benefit for everyone,” he said.
California’s law has been more complicated.
When it was proposed last year, the state court system objected to a provision that would have allowed the police to ticket autonomous vehicles, arguing that traffic laws were written to apply to human drivers — not companies with huge driverless fleets.
So Phil Ting, a Democrat who sponsored the bill and was in the State Assembly at the time, removed that provision.
“Unlike human drivers like you and me, it is very difficult to put autonomous vehicles into that system,” he said in an interview. “We have a point system. Our licenses can get withheld. Our insurance will go up. None of that accountability against a human driver really works against an autonomous vehicle company.”
Mr. Ting rewrote the law so that it asked the California Department of Motor Vehicles to develop rules for the “notices of noncompliance” and penalties associated with those notices. The department did not immediately respond to a request for comment.