The incident occurred on Saturday evening after a fire at a Pacific Gas & Electric (PG&E) substation knocked out electricity across roughly one-third of the city. The outage affected about 130,000 residents, forced some businesses to shut temporarily and caused traffic lights to stop functioning in several areas. In response, Waymo paused its ride-hailing service later that evening.
During the outage, several Waymo robotaxis stalled at intersections, as shown in videos shared on social media. The vehicles were seen with hazard lights activated while traffic congestion worsened on already busy streets.
Waymo explained that its autonomous vehicles are designed to navigate intersections with non-functioning traffic signals by treating them as four-way stops. However, in certain situations the vehicles request a confirmation check from support systems. The widespread outage led to a sharp increase in such requests.
“While we successfully traversed more than 7,000 dark signals on Saturday, the outage created a concentrated spike in these requests,” the company said. “This created a backlog that, in some cases, led to response delays contributing to congestion on already-overwhelmed streets.”
The company acknowledged that its confirmation protocols were developed during earlier stages of deployment and said it is now refining them to better reflect the scale of its current operations. Waymo said it is rolling out fleet-wide software updates that will provide vehicles with clearer context during power outages, enabling them to navigate more decisively. It also plans to enhance its emergency response procedures based on lessons learned from the incident.
Waymo operates more than 2,500 autonomous vehicles across several U.S. cities, including the San Francisco Bay Area, Los Angeles, Metro Phoenix, Austin and Atlanta. The company confirmed that its San Francisco Bay Area ride-hailing service resumed on Sunday.
Regulators are taking note of the disruption. On Monday, the California Public Utilities Commission (CPUC) said it was reviewing the issue involving the stalled vehicles. The CPUC, alongside California’s Department of Motor Vehicles, oversees the testing and commercial deployment of robotaxis in the state.
The incident adds to recent scrutiny of Waymo’s operations. Earlier this month, the company issued a software recall after Texas officials reported that Waymo vehicles had illegally passed stopped school buses multiple times since the start of the school year. That development prompted the U.S. National Highway Traffic Safety Administration to open an investigation in October.
As autonomous vehicle services continue to expand, the San Francisco outage has highlighted the challenges of scaling self-driving technology in complex, real-world emergency conditions.