On December 20, 2025, a major power outage struck San Francisco, United States. The blackout was triggered by a fire at a substation, plunging approximately 130,000 users into darkness and causing a significant number of traffic lights to cease functioning.

Alphabet's Waymo autonomous taxis, which rely on recognizing traffic signals for navigation, found themselves at a loss. They were unable to identify the non - operational traffic lights. As a result, the system frequently prompted for manual confirmation from the passengers or remote operators. This led to a situation where multiple vehicles came to a halt, causing severe traffic congestion in the affected areas.

Although Waymo managed to address the issue with 7,000 malfunctioning traffic lights, the sudden surge in manual confirmation requests overwhelmed the system. Responses were significantly delayed. In light of this, the company had no choice but to temporarily suspend its autonomous taxi services.

This incident has laid bare the vulnerability of autonomous driving technology when faced with urban infrastructure failures. It has also heightened public concerns regarding the ability of autonomous vehicle operators to effectively manage major emergencies, such as earthquakes and floods, which could cause even more widespread and chaotic disruptions to the normal functioning of cities.