Three days after a cascading power failure left Waymo vehicles stranded across San Francisco, the autonomous vehicle company is racing to patch a critical vulnerability: what happens when traffic lights go dark. The Alphabet-owned robotaxi operator announced immediate fleet-wide updates designed to help its cars navigate intelligently when infrastructure fails, signaling that even the most ambitious autonomous systems need backup plans for the real world.
The incident exposed a blindspot in autonomous driving technology that's rarely discussed outside engineering circles. When Waymo vehicles encountered dead traffic lights during Saturday's widespread blackout, they essentially lost their ability to navigate safely through intersections. The system wasn't designed to gracefully degrade when core infrastructure vanishes.
San Francisco's Saturday afternoon power failure was brutal in scope. A fire at a PG&E substation created what the utility called "significant and extensive" damage, leaving roughly 130,000 customers without power at peak outage. By Sunday morning, 21,000 still sat in darkness. The timing couldn't have been worse for Waymo, which was running peak-hour service when the grid collapsed.
Social media filled with videos showing multiple Waymo vehicles stranded in gridlocked traffic across neighborhoods like the Mission and SOMA. What the footage doesn't capture is the actual decision-making happening inside those vehicles: sensors registering non-functional signals, AI systems unable to confidently proceed, and the resulting paralysis. "We directed our fleet to pull over and park appropriately so we could return vehicles to our depots in waves," Waymo said in a blog post late Tuesday. "This ensured we did not further add to the congestion or obstruct emergency vehicles during the peak of the recovery effort."
