Update, August 19, 2026: Three days after the outage Waymo published its own write-up: the driver is trained to treat a dark signal as a four-way stop; the fleet still “traversed more than 7,000 dark signals” that Saturday; remote confirmation checks spiked. CNBC said Waymo then pushed a fleet update so cars would need fewer remote checks. Tesery’s same-day Tesla piece is a different product: a supervised FSD clip, not an empty Tesla taxi fleet.
On Saturday, December 20, 2025, a PG&E substation fire blacked out a large part of San Francisco. Traffic lights went dark. BBC, The Guardian, and ABC7 showed Waymo robotaxis sitting in intersections with hazard lights on while other drivers went around them. Waymo paused its San Francisco ride-hail service that day after the city asked about the congestion.
That is a real operational failure for a driverless taxi: no one in the front seat, cars blocking live traffic. It is not proof that “Waymo cannot drive in the dark,” and it is not a Tesla FSD victory lap. This article is the Waymo/city record. The Tesla video is next door.
Key facts
- When: December 20, 2025. PG&E outage; well over 100,000 customers in western San Francisco in contemporaneous reports.
- What failed first: Utility power and traffic signals. The city was already gridlocked.
- What Waymo cars did: Some stopped at dark signals with hazards on. Videos circulated the same night.
- What Waymo did: Paused SF service that Saturday. On December 23 it said it crossed thousands of dark signals and that remote checks spiked.
- What this is not: A crash-injury event Waymo reported that day, or a CPUC ban on Waymo in San Francisco.
What Waymo said happened
Waymo’s December 23 blog said dark signals are supposed to be four-way stops, and that a citywide outage created a concentrated spike in confirmation checks — remote humans signing off when the stack was unsure. Cars waiting on those checks sat in intersections. That is narrower than “the cars forgot how to move,” and it is still a problem: a robotaxi that needs a remote OK at every dark light will freeze a blacked-out downtown.
The company said it would change how the fleet treats that case. CNBC reported a software/fleet update so vehicles would need fewer remote checks next time. Tesery’s later Santa Monica charging lawsuit is a different Waymo-vs-city fight (noise at night lots, not dark signals).
Driverless vs supervised
Waymo’s SF taxis that night had no driver who could grab a wheel. Tesla’s same-week clip was Full Self-Driving (Supervised) on a Model Y with a human still responsible. Comparing those two videos as one “autonomy test” is the error the original Tesery magazine copy made. California’s later robotaxi-ticket law is about driverless cars, not owner FSD.
FAQ
Did every Waymo in San Francisco freeze?
No. Waymo said it crossed more than 7,000 dark signals and paused because checks spiked and some cars were blocking streets.
Did Waymo stay down?
It paused Saturday. Service came back after the city and the grid began to recover. Check Waymo’s app for current SF status; this story is December 2025.
Did Tesla Robotaxis keep running paid SF rides?
Tesla did not show that. See Tesery’s supervised FSD video note.
For riders: a dark signal is a four-way stop whether the car is a Waymo or a human. For Tesla owners: this outage does not change FSD (Supervised) on your car.
Featured photo: a Waymo Jaguar I-Pace in San Francisco (file photo, 2023; not a blackout still). Image via Wikimedia Commons.
Related: Tesla’s supervised FSD clip the same weekend · Waymo v. Santa Monica overnight charging · California’s robotaxi-ticket law
