Waymo explains why its automated robot stopped during a power outage in SF

Waymo is shipping a software update to help its robot navigate broken traffic lights during power outages “more decisively,” the company said Tuesday in a blog post explaining why its self-driving vehicles stopped at intersections during a power outage in San Francisco last weekend.

Waymo said the self-driving system in its robo-taxi treats dead stop lights as four-way stops, just as humans are supposed to do. This should have allowed the bots to function normally despite the massive outage.

Instead, many vehicles requested a “confirmation check” from Waymo’s fleet response team to make sure what they were doing was correct. All Waymo robotic vehicles have the ability to perform these confirmation checks. Waymo said that with this widespread outage on Saturday, there was a “concentrated spike” in these confirmation requests, which helped create all the congestion that was captured on video.

Waymo said it built this confirmation request system “out of an abundance of caution during our early deployment” but is now improving it “to fit our existing scale.”

“Although this strategy has been effective during small outages, we are now implementing fleet-wide availability updates [self-driving software] “With the specific context of a power outage, allowing it to navigate more decisively,” the company wrote.

The software update will add “more context around regional outages” to the company’s self-driving software. Waymo also said it will improve its emergency response protocols by “incorporating lessons learned from this event.”

While much focus has been placed on instances where Waymo’s robotaxis malfunctioned during power outages, the company shared that its vehicles “successfully passed more than 7,000 dark signals on Saturday.”

“Navigating an event of this size presents a unique challenge for autonomous technology,” the company wrote.

Saturday’s chaos is the latest example of how Waymo continues to uncover unexpected problems with its software and approach to designing a reliable fleet of self-driving vehicles. The company has already had to ship multiple software updates to make its robotaxis wait for parked school buses, triggering a National Highway Traffic Safety Administration investigation and leading to a recall.