Waymo is shipping a software update to help its robotaxis navigate disabled traffic lights during power outages “more decisively,” the company said Tuesday in a blog post that explains why its self-driving vehicles got stuck at intersections during a blackout in San Francisco this past weekend.
Waymo said the self-driving system in its robotaxis treat dead stop lights as four-way stops, just like humans are supposed to. That should have allowed the robotaxis to operate normally in spite of the massive outage.
Instead, many of the vehicles requested a “confirmation check” from Waymo’s fleet response team to make sure what they were doing is correct. All Waymo robotaxis have the ability to make these confirmation checks. With such a wide-spread outage on Saturday, there was a “concentrated spike” in these confirmation requests, Waymo said, which helped create all the congestion caught on video.
Waymo said it built this confirmation request system “out of an abundance of caution during our early deployment” but that it is now refining it to “match our current scale.”
“While this strategy was effective during smaller outages, we are now implementing fleet-wide updates that provide the [self-driving software] with specific power outage context, allowing it to navigate more decisively,” the company wrote.
The software update will add “even more context about regional outages” to the company’s self-driving software. Waymo also said it will improve its emergency response protocols by “incorporating lessons from this event.”
While a lot of focus has been placed on the instances where Waymo’s robotaxis got stuck during the power outage, the company shared that its vehicles “successfully traversed more than 7,000 dark signals on Saturday.”
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“Navigating an event of this magnitude presented a unique challenge for autonomous technology,” the company wrote.
Saturday’s mess is the latest example of how Waymo is still uncovering unforeseen issues with its software and its approach to designing a reliable fleet of self-driving vehicles. The company already had to ship multiple software updates to make its robotaxis wait for stopped school buses, which prompted a National Highway Traffic Safety Administration investigation and led to a recall.
