Waymo’s robotaxi fleet hit a high-profile snag last weekend, turning a San Francisco blackout into something out of a tech dystopia.
A substation fire left a third of the city without power, traffic lights went dark, and Waymo’s autonomous cars, normally lauded for their ability to handle tricky intersections, stalled in droves.
Videos across social media showed multiple vehicles idling in the same junction, hazard lights blinking in synchrony, while human drivers circled helplessly around them.
The company suspended service across the affected area for roughly 18 hours.
A Waymo spokesperson said: “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.”
It was a reminder that even fleets designed to be autonomous can be surprisingly dependent on functioning infrastructure, something Londoners will soon be watching closely when Waymo rolls into the city in 2026.
With narrower streets, denser traffic, and far less patience among pedestrians and drivers, the stakes are even higher across the pond.
An ‘overwhelmed’ system
The outage’s root cause, according to Waymo, was a backlog in handling so-called “dark intersections.”
Vehicles encountering a nonfunctional signal normally treat it as a four-way stop, and if uncertain, ping Waymo’s remote operations team for guidance.
But during last week’s blackout, the sheer number of simultaneous dark signals overwhelmed the system, leaving cars stuck in place.
“In limited instances on Saturday night, the [robotaxi] Driver sought additional context,” Waymo said.
“However, the unprecedented scale of the power outage and its impact on local connectivity resulted in some delays to those confirmations.”
Rodney Brooks, founder of iRobot, argued that the fleet’s paralysis was an inevitable “edge case” – a rare, unpredictable event.
“You think you have a bunch of problems solved, and then there’s something you hadn’t considered”, Brooks added.
Even Elon Musk couldn’t resist weighing in, using the mishap as a boast of his own fleet: “Tesla Robotaxis were unaffected by the [San Francisco] power outage,” he posted on his own platform.
The London test
San Francisco’s outage goes beyond a cautionary tale, as it forecasts the potential challenges awaiting autonomous fleets in older, more complex cities.
London’s streets, with their labyrinthine layouts, roundabouts, and notorious congestion, will present a tougher test than the suburban expanses and grid systems of California.
Waymo says it is already incorporating lessons from San Francisco. “We are already learning and improving from this event,” the spokesperson said.
Still, the episode raises questions for investors and city planners alike. How will autonomous systems respond when infrastructure fails? And, how many could be put in danger if it all goes wrong?
For UK regulators, the outage shows that trials should include stress-testing for truly chaotic scenarios, be they sudden outages, flash floods, or a double-decker bus stopping when it shouldn’t.
A Waymo coming to a grinding halt at an intersection may be technically safe. A city gridlocked behind it, however, seems like a far less appealing proposition.