Waymo reported that 96% of its vehicles' stoppages during the December 2025 blackout resolved autonomously, but the remaining vehicles blocked intersections and hindered first responders.

“Multiple news outlets reported a widespread power outage in San Francisco on December 20, 2025, during which Waymo's autonomous vehicles stalled in intersections, blocked traffic, and prompted the company to suspend service. A subsequent city hall hearing in March 2026 discussed how these stalled vehicles impeded first responders. However, while Waymo stated that "most" trips completed successfully, the specific figure of 96% of stoppages resolving autonomously could not be found in any of the reports covering the incident. Context: The incident occurred on December 20, 2025, when a substation fire caused a major blackout. The scale of the outage overwhelmed Waymo's system, which is designed to treat individual dark signals as four-way stops but could not handle thousands of simultaneous requests for remote confirmation.”