Waymo Shares What Caused SF Robotaxi Stalls

On Saturday, a power outage in San Francisco knocked out traffic lights in several neighborhoods. Some Waymo robotaxis stalled at intersections, and the company temporarily paused its ride-hailing service as the situation worsened.

The aftermath was swift: traffic congested, videos went viral, and the event became a reality check for robotaxi technology reacting in a city emergency. City officials called for quicker removal of the vehicles, and regulators took a closer look at what happened next.

Waymo's take: The real bottleneck behind the stalls

That's what the insiders say. Waymo asks people to look beyond the "cars stopped" headline and see the real bottleneck: a safety process that worked smoothly at small scale but overloaded when the city stopped behaving normally.

Their explanation becomes largely about the internal mechanics. The Waymo Driver treats dark traffic signals as four-way stops but in some cases may initiate a sort of "confirmation check" to double-check the safest option. The outage produced a spike in those checks, resulting in a backlog that slowed responses in some cases and contributed to congestion.

One important statistic: over 7,000 dark signals passed that day without problem. The point being that most intersections worked as they were supposed to, even as a smaller number of chokepoints set off enough verification checks to delay vehicles at precisely the worst moment.

The outage scale that worsened things

The blackout was significant: Reuters reported it started with a fire at a PG&E substation and hit about 130,000 customers, with traffic signals down across town. When signals fail citywide, caution compounds—most of all when scores of vehicles strike the same ambiguous intersections in a short window.

What Waymo did during the blackout

Waymo outlined its field response: the pause in service instructed the vehicles to pull over, park, and return the cars to depots in waves to avoid adding to congestion and keep streets free for emergency responders. Local reporting adds that city leaders pressed Waymo to be more proactive about removing its vehicles from the roads during the incident.

What changes are coming

The fixes are in. Waymo plans a fleetwide software update to give vehicles more "power outage context," so they can navigate dark-signal intersections more decisively. It also plans to update emergency-response protocols based on what happened in San Francisco.

The approach also depends on coordination and training. Waymo says it has trained over 25,000 first responders and will expand engagement and refresh training based on the lessons from large-scale events.

Why this matters next

Regulators are watching. In a reminder that reliability is not only a product issue but a licensing and public-safety matter for robotaxi operators, Reuters reported that regulators in California are reviewing the incident.

Zooming out, the story looks familiar to anyone tracking automation beyond cars; many automated systems fail not because the model can’t do the task but because safety gates get overloaded when the world shifts quickly. Waymo’s explanation argues that the safety gate was too conservative for a city-scale outage and that the next update must preserve caution without creating gridlock. 

If the update cuts the confirmation-check backlog without sacrificing safety, the blackout could become a blueprint for how robotaxi fleets degrade gracefully under infrastructure failure. If not, the next major outage won't just be a traffic headache, it'll be a repeatable public test of whether autonomous mobility can scale when the city goes off-script.