A major power outage in San Francisco turned Waymo’s self-driving fleet into rolling roadblocks, as the company’s autonomous cars encountered dark intersections, stopped, and then mostly refused to move.
The vehicles didn’t lose power or crash their software, but they did revert to such a cautious fail-safe mode that they effectively “bricked” themselves in heavy traffic, forcing Waymo to suspend service while crews worked to clear the streets.
Riley Walz
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How a blackout turned robotaxis into roadblocks
The chain reaction began when a fire at a substation caused a widespread power outage, knocking out power to traffic lights in large parts of the city. Waymo’s cars are programmed to treat dark signals as four-way stops, and in some cases require remote “confirmation” from human supervisors before proceeding. During normal operations, this remote layer is intended as a safety net.
During the outage, thousands of signals went out at once, causing a huge spike in requests for human review. The emergency line couldn’t keep up, so cars simply waited at intersections and lanes for approvals that arrived too slowly or not at all. On the ground, that looked like clusters of self-driving Jaguars sitting motionless with their hazard lights on, sometimes stacked nose to tail and blocking buses, crossing traffic and turning lanes. To nearby drivers and pedestrians, it felt less like advanced AI and more like a fleet of very expensive bollards.
An autonomous Waymo car charges its battery at a Charge Point charging station in Hoboken, New Jersey.Getty Images
Waymo’s explanation fits into a pattern of security research
Waymo says the problem wasn’t that the software couldn’t handle any dark intersections; The company points out that its cars have correctly navigated thousands of intersections affected by power outages. Instead, the outage is described as a systems problem: the outage created too many edge cases at once, overloading remote support and trapping vehicles in conservative, fail-safe logic. Waymo has promised software and operational changes so cars can more intelligently recognize large-scale disruptions and prioritize stopping instead of sitting in the middle of intersections.
The blackout incident is in addition to the existing security investigation. Earlier this year, Waymo issued a software recall after its robotaxis had problems school buses stopped. There’s also been a steady rhythm of lower-speed scrapes and strange behavior in San Francisco, from blocked emergency scenes to awkward interactions with cyclists and pets.
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A stress test as Waymo plans to expand
The optics are difficult for a company that actively markets robotaxis as a practical replacement for a second car. Waymo has already outlined plans to expand its driverless service to other markets. The San Francisco blackout brought to light another question: how resilient these systems are when infrastructure fails in ways that affect thousands of intersections at once.
Waymo’s response, suspending service, promising fixes and cooperating with regulators, suggests it understands the stakes. For city drivers and motorcyclists, the outage will be remembered as an early stress test of a technology that must handle not only daily traffic, but also rare, messy outages across the city, without turning into a fleet of stranded obstacles.
This story was originally published by Autoblog on December 25, 2025, where it first appeared in the News section. Add Autoblog as a preferred source by clicking here.
