Waymo, the self-driving unit of Alphabet, said on Tuesday it will update the software that operates its autonomous vehicles and improve emergency response procedures after a widespread power outage caused several of its robotaxis to stall in parts of San Francisco over the weekend.
The company paused service on Saturday evening after a fire at a substation operated by Pacific Gas and Electric cut power to roughly one-third of the city, affecting about 130,000 residents and forcing some businesses to temporarily close. The outage also knocked out traffic lights at numerous intersections, leading to congestion.
Videos shared on social media showed Waymo vehicles stopped at intersections with hazard lights activated as traffic signals went dark. Waymo said its autonomous systems are designed to handle unlit signals as four-way stops but may request additional confirmation in certain cases.
“While we successfully traversed more than 7,000 dark signals on Saturday, the outage created a concentrated spike in these requests,” Waymo said in a statement. “This created a backlog that, in some cases, led to response delays contributing to congestion on already-overwhelmed streets.”
Waymo said the confirmation protocols were appropriate during early deployment but are now being refined to reflect the scale of its operations. The company is rolling out fleet-wide updates that provide vehicles with “specific power outage context, allowing it to navigate more decisively,” and said it would also strengthen emergency response procedures based on lessons from the incident.
Waymo operates more than 2,500 vehicles across the San Francisco Bay Area, Los Angeles, Metro Phoenix in Arizona, Austin in Texas and Atlanta in Georgia. The company said ride-hailing services in the Bay Area resumed on Sunday.
On Monday, the California Public Utilities Commission said it was reviewing the incident involving stalled Waymo vehicles. The commission, alongside California’s Department of Motor Vehicles, oversees permits for the testing and commercial deployment of robotaxis.
Earlier this month, Waymo issued a recall to update its autonomous driving software after officials in Texas said its vehicles had illegally passed school buses at least 19 times since the start of the school year. The incidents prompted the National Highway Traffic Safety Administration to open a probe in October.
