On December 20, 2025, Waymo robotaxis stalled across San Francisco amid a major blackout triggered largely by a fire at a PG&E substation near 8th and Mission Streets, leaving tens of thousands of residents without power and snarling traffic as autonomous vehicles ground to a halt at darkened intersections. The incident not only disrupted ride-hail services and public transit but also laid bare the challenges autonomous systems face when core infrastructure fails — from traffic signals to communications networks.
Why Waymo Robotaxis Stalled
Waymo robotaxis were halted in San Francisco on December 20, 2025 because the widespread blackout knocked out power to traffic signals, cloud connectivity, and critical infrastructure feeds the vehicles rely on — forcing the company to temporarily suspend service for safety. The outage, caused in part by a fire at a PG&E substation, left roughly 130,000 customers without electricity and forced transit agencies like BART and Muni to reroute or bypass services.
The Blackout That Knocked San Francisco Offline
What Happened — Substation Fire and Power Loss
On Saturday, Dec. 20, 2025, San Francisco was hit by a significant power outage that ultimately affected around 125,000–130,000 PG&E customers, or roughly 30% of the city’s electrical grid, with outages reported across neighborhoods including Richmond, Sunset, Presidio, Hayes Valley, and parts of downtown.
While PG&E had not fully confirmed an official root cause in early reporting, fire department officials and multiple outlets noted an active fire at a key substation near 8th and Mission Streets in the South of Market area — likely a contributing factor to the sprawling blackout.
The outage began in the morning around 9:40 a.m. and spread throughout the day. Firefighters responded to the substation blaze around 2:15 p.m., largely containing it by mid-afternoon, though the damage and power instability continued to disrupt the grid.
Power Restoration Efforts and Timeline
After the blackout expanded through the afternoon, PG&E crews began partial restorations in some areas, with estimates for some households set around mid-late afternoon (circa 3:30 p.m.–3:45 p.m.), while others remained dark into the evening and night as crews assessed damage and repaired lines.
City officials and utility spokespeople cautioned that full restoration would vary by neighborhood and that the complex web of outages meant some pockets of customers would remain without power overnight.
Transit Chaos — From BART to Muni to Traffic Lights
Public Transit Disruptions During the Outage
The blackout wasn’t just about dark homes — it wreaked havoc on transportation systems. Bay Area Rapid Transit (BART) reported closures or route bypasses for key stations such as Powell Street and Civic Center, while San Francisco’s Muni Metro trains were unable to enter underground stations like Powell, Civic Center, or Van Ness due to the lack of power.
With electrified train systems essentially dead in parts of the city, transit officials had no choice but to reroute surface routes or suspend service in impacted corridors, leaving commuters scrambling for alternatives.
Darkened Intersections and Safety Challenges
Perhaps most consequential for surface traffic were the dark traffic lights and inoperative street signals, which created intersections where right-of-way rules collapsed into chaos. City emergency management urged drivers to treat non-functioning lights as four-way stops and to avoid unnecessary travel — warnings that underscored the safety risks the blackout posed to drivers, pedestrians, and responders alike.
Why Waymo’s Robotaxis Stalled
Reliance on Infrastructure and Connectivity
Waymo’s autonomous vehicles depend heavily on a combination of street infrastructure feeds (including traffic signal data), wireless connectivity for map and routing updates, and highly reliable power systems for onboard sensors like LiDAR and forward-facing cameras. When those systems fail or become intermittent, safety protocols dictate that vehicles should pull over or halt operations to avoid unpredictable or unsafe driving decisions.
In this sanctuary city’s blackout, that dependency became a liability:
- Traffic signals went dark, removing a key citywide synchronization input for autonomous navigation.
- Power loss likely degraded data links and sensor feeds the vehicles use to interpret intersections.
- The company’s safety protocols triggered service suspension to prioritize rider and public safety.
In plain terms: without reliable power and infrastructure cues, the Waymo stack errs on the side of stopping, not guessing — a cautious posture that, while safe, caused vehicles to sit idle at intersections.
Service Pause for Public Safety
On Saturday evening, GOOGL-owned Waymo confirmed that it had temporarily suspended its robotaxi service in San Francisco amid the outage and traffic chaos, prioritizing safety, and allowing emergency personnel unobstructed access to congested streets.
This wasn’t a localized glitch; videos and social reports around the city showed multiple Waymo vehicles stuck at dark intersections, contributing to congestion and prompting concerns from both citizens and responders.
On the Streets — Local Reaction and Reports
Citizen-Reported Sightings and Frustration
Amid the blackout, social media and local forums captured neighborhood narratives of Waymo cars sitting squarely in the middle of intersections with dead lights, with some residents joking or lamenting that the autonomous cars were “bricked” until power returned. These exchanges reflected a broader public mix of frustration, amusement, and concern:
- Some users reported vehicles blocking traffic lanes and interfering with symbolically human traffic navigation.
- Others mused about the “failsafes” or lack thereof in autonomous fleet logic.
This anecdotal reaction, though unverifiable as hard data, aligned with what you’d expect when advanced tech meets unexpected infrastructure failure — edge case scenarios that often don’t appear until real emergencies unfold.
Broader Impacts — Businesses, Safety, and Holiday Weekend Chaos
Local Economy and Holiday Weekend Setbacks
The outage struck one of the busiest weekends ahead of Christmas, hitting local businesses hard as lights went out mid-day. Restaurants, cafes, shops, and holiday markets were forced to close doors early or restrict operations to cash only, straining small business cash flows during a peak shopping period.
Residents improvised with candles or acoustic gatherings as parts of the city plunged into darkness — a real-world reminder that even tech hubs remain vulnerable to back-to-basics living during grid instability.
Safety Alerts and Emergency Management
The San Francisco Department of Emergency Management took to social platforms urging caution around nonfunctional lights, advising residents to avoid unnecessary travel unless absolutely essential, and cautioning about widespread traffic snarls.
Emergency operators asked the public not to call 911 simply to report outages, focusing dispatch resources on life-threatening emergencies — a nuanced but essential message in managing community response during crises.
What This Means for Autonomous Vehicles Going Forward
This incident underscores a reality many in the field have warned about: autonomous systems are only as robust as the infrastructure that supports them. When power grids, signal networks, and data links fail, the safest technical choice — to stop — may still create secondary hazards such as blocked intersections and confused human drivers.
For planners and technologists alike, the San Francisco blackout becomes a case study in resilience engineering: how do self-driving vehicles adapt to infrastructure calm and infrastructure chaos with equal facility? And who must take responsibility when systems interact in unpredictable ways?
Conclusion: A Blackout That Tested Tech and Transit
The Dec. 20, 2025 San Francisco blackout revealed much more than just a failing substation — it exposed how deeply modern urban life, from transit to autonomous vehicles, hinges on continuous power and coordinated infrastructure signals. Waymo’s robotaxis stalled not because they “failed,” but because they followed safety logic in a system where key inputs were suddenly unavailable.
As the city works to rebuild and restore, and as Waymo and other AV operators review this unexpected stress test, one thing is clear: urban autonomy must learn to navigate the unexpected alongside humans, not just in ideal conditions.
