Last year, two Waymo robotaxis in Phoenix “made contact” with the same pickup truck that was in the midst of being towed, which prompted the Alphabet subsidiary to issue a recall on its vehicles’ software. A “recall” in this case meant rolling out a software update after investigating the issue and determining its root cause.

In a blog post, Waymo has revealed that on December 11, 2023, one of its robotaxis collided with a backwards-facing pickup truck being towed ahead of it. The company says the truck was being towed improperly and was angled across a center turn lane and a traffic lane. Apparently, the tow truck didn’t pull over after the incident, and another Waymo vehicle came into contact with the pickup truck a few minutes later. Waymo didn’t elaborate on what it meant by saying that its robotaxis “made contact” with the pickup truck, but it did say that the incidents resulted in no injuries and only minor vehicle damage. The self-driving vehicles involved in the collisions weren’t carrying any passenger.

After an investigation, Waymo found that its software had incorrectly predicted the future movements of the pickup truck due to “persistent orientation mismatch” between the towed vehicle and the one towing it. The company developed and validated a fix for its software to prevent similar incidents in the future and started deploying the update to its fleet on December 20.

Waymo’s rival company Cruise was involved in a more serious incident last year, wherein one of its robotaxis accidentally dragged someone hit by another vehicle a few dozen feet down a San Francisco street. California then suspended its license to operate in the state, and Cruise eventually paused all robotaxi operations, even the ones with a human driver behind the wheel, as part of a safety review. Meanwhile, it’s business as usual for Waymo, which recently announced that it will start testing driverless vehicles on highways and freeways in and around Phoenix.