Waymo halted its autonomous taxi operations in San Francisco on Saturday evening following a major power outage that left numerous vehicles immobilized on roadways. Social media was flooded with images and videos showing Waymo’s driverless cars stopped at intersections, forcing human drivers to either wait behind them or navigate carefully around them. The company confirmed it had paused service in response to the blackout. “The power failure was a citywide incident that led to significant gridlock across San Francisco, including non-operational traffic signals and disruptions to public transit,” a spokesperson explained. “Although the utility infrastructure failure was substantial, we are dedicated to improving how our technology handles traffic flow during similar situations.”

The spokesperson further noted that Waymo is “concentrating on quickly applying insights gained from this event and remains dedicated to building and preserving the trust of the communities we serve daily.”

The outage also disabled many of the city’s traffic lights and impacted Muni public transit, prompting San Francisco Mayor Daniel Lurie to advise residents to avoid unnecessary travel. Waymo clarified that while its autonomous systems are programmed to treat malfunctioning traffic lights as four-way stops, the extensive nature of Saturday’s blackout resulted in some vehicles pausing longer than usual as they evaluated intersection conditions. The company added that most active trips were finished successfully. The blackout is believed to have originated from a fire at a Pacific Gas & Electric substation within the city. Reports indicate approximately 120,000 PG&E customers were impacted by the outage; although power was restored to most by late Saturday, around 35,000 customers remained without electricity on Sunday morning. PG&E’s website also reflected thousands of San Francisco customers still affected at that time.

A recently leaked letter from Tiger Global Management revealed that Waymo is currently completing 450,000 autonomous rides weekly—nearly double the figure the Alphabet-owned company shared earlier this spring. This post has been updated to include Waymo’s announcement that service is now resuming.