Power outage paralyzes Waymo robotaxis when traffic lights go out

San Francisco was affected by a massive power outage over the weekend. It started with a fire at a substation in the city on Saturday afternoon, causing a blackout that at times affected as much as a third of the city, leaving more than 130,000 homes without power. Among the city’s affected critical systems were the traffic lights, which paralyzed Waymo’s fleet of robotaxis, stopping them in their tracks and clogging traffic.

Any recent visitor to San Francisco can’t help but notice the profusion of sensor-festooned autonomous vehicles on the roads, especially the all-white Jaguar I-Paces that belong to Waymo. The robotaxi company has more than 800 AVs in its Bay Area fleet; that can feel like a conservative estimate when you see five or six at a time—invariably with no occupants—within a block.

The cars navigate the city, combining high-resolution maps with inputs from lidar, optical, and other sensors on the upfitted Jags. The cars drive conservatively, but they can get confused in edge cases—earlier this month, Waymo issued a recall to fix a problem in which its robotaxis would illegally pass stopped school buses.

When the traffic lights went out, Waymo’s robotaxis got a little too cautious at intersections. With no red-yellow-green to cue drivers, the rule is to treat the intersection as a four-way stop. Indeed, Waymo’s cars are programmed to do this, but it seems the scale of the outage over the weekend was just too much to handle.

Social media and Reddit began to fill with videos of stationary Waymos at intersections, and the company temporarily suspended service.

Most areas saw power restored by noon yesterday, although Pacific Gas and Electric said it expected some power to remain out until Monday afternoon.

Meanwhile, Waymo’s robotaxis are up and running again. “We are resuming ride-hailing service in the San Francisco Bay Area,” a company spokesperson told Ars. “Yesterday’s power outage was a widespread event that caused gridlock across San Francisco, with non-functioning traffic signals and transit disruptions. While the failure of the utility infrastructure was significant, we are committed to ensuring our technology adjusts to traffic flow during such events.”

“Throughout the outage, we closely coordinated with San Francisco city officials. We are focused on rapidly integrating the lessons learned from this event and are committed to earning and maintaining the trust of the communities we serve every day,” Waymo said.