Waymo to Update Software Across Fleet After Major Power Failure

Alphabet Inc.’s Waymo said it would strengthen its automated software to better handle power outages after its self-driving taxis froze and caused traffic jams during a major electricity failure last weekend in San Francisco.

The Waymo Driver system is programmed to handle dark traffic signals in the same manner as four-way stops, but a car will occasionally “request a confirmation check to ensure it makes the safest choice,” the company said Tuesday in a statement. While the vehicles “successfully” handled 7,000 traffic signals that were knocked out by San Francisco’s power failure on Dec. 20, the outage “created a concentrated spike in these requests,” the company said.

The spike delayed Waymo’s response time to its stalled vehicles. When city officials urged motorists to stay off the streets, Waymo said it suspended service.

Related: Waymos Froze, Blocked Traffic During San Francisco Power Outage

The power failures, touched off by a fire at a PG&E Corp. substation, rolled through San Francisco during the weekend, at one point affecting about 130,000 customers. Social media videos showed multiple Waymo vehicles stopped in the middle of streets with their hazard lights flashing, creating massive backups.

The company said it was taking steps to integrate more information in its software about the “context” of regional power outages, letting the vehicles “navigate these intersections more decisively.” Waymo also is working with San Francisco Mayor Daniel Lurie on emergency response protocols and updating its first responder training.

Photo: A Waymo autonomous taxi on Bush Street in San Francisco, California. (David Paul Morris/Bloomberg)