San Francisco autonomous vehicle company Cruise recalled the software of its fleet of 300 cars after one of its taxis rear-ended a Muni bus when the car’s software got confused by the articulated vehicle, according to a federal safety report and the company.
Since last month’s low-speed crash, which resulted in no injuries, Cruise CEO Kyle Vogt said the company chose to conduct a voluntary recall, and the software update assured such a rare incident “would not recur.”
It was not the first San Francisco incident involving Cruise since June, when it became the first company in a major city to win the right to taxi passengers in driverless vehicles — in this case Chevrolet Bolts. The city’s Municipal Transportation Agency and County Transportation Authority recorded at least 92 incidents from May to December 2022 in which autonomous ride-hailing vehicles caused problems on city streets, disrupting traffic, Muni transit and emergency responders, according to letters sent to the California Public Utilities Commission.
The latest incident happened March 23, when a driverless Cruise AV “inaccurately predicted the movement” of an articulated Muni bus, a type of coach with a rubber center that allows the front and back to flex, according the company’s April 3 filing with the National Highway Traffic Safety Administration.
“In this incident, the (software) initially perceived both sections of the bus as the bus was pulling out of a bus stop in front of the AV,” the company said in the report. “As the bus proceeded forward into the AV’s lane of travel, the rear section of the bus obstructed the front section.”
When the bus slowed, the software “inaccurately determined that the bus was continuing to move forward in traffic based on the anticipated behavior of the front section of the bus, which was by then obstructed, and the (automated driving system) commanded the AV to begin decelerating too late to avoid a rear-end collision with the bus,” the filing said.
Vogt elaborated on the crash Friday in a blog post. He said the Cruise car was traveling about 10 mph at the time and the collision caused minor damage to its front fender.
“We do not expect our vehicles to run into the back of a city bus under any conditions, so even a single incident like this was worthy of immediate and careful study,” he wrote.
Within two days, company investigators determined that the cause was the unique feature of the articulated bus, Vogt said.
“This caused an error where the (car) reacted based on the predicted actions of the front end of the bus (which it could no longer see), rather than the actual actions of the rear section of the bus,” Vogt said. “That is why the AV was slow to brake.”
Such unusually shaped vehicles have caused problems before. Federal investigators suspect a Tesla was on autopilot in February when it crashed into a parked East Bay firefighter ladder truck — another uniquely shaped vehicle — killing the driver and injuring four firefighters. Highway safety investigators are looking into other Tesla autopilot crashes involving parked emergency vehicles assisting with other crashes, saying there have been at least 15 such instances.
Just two days before the Cruise crash in March, the company had more problems with Muni during one of San Francisco’s intense spring storms. A falling tree brought down a Muni line near Clay and Jones streets on March 21, and a witness reported on social media that two Cruise cars drove through caution tape into the downed wire.
A company representative said neither car had passengers and teams were immediately dispatched to remove the vehicles.
On Jan. 22, a driverless Cruise car entered an active firefighting scene and nearly ran over hoses. Fire crews broke a car window to try to stop it.
Such incidents have led some San Francisco transportation officials to warn state regulators about possible danger.
Seeing the reported incidents “all together on a list or a map, it does give us pause, and we are concerned about the severity of some of them,” Tilly Chang, executive director of the County Transportation Authority, said in January.
As for the March bus collision, Vogt said the software fix was uploaded to Cruise's entire fleet of 300 cars within two days. He said the company’s probe found the crash scenario “exceptionally rare” with no other similar collisions.
“Although we determined that the issue was rare, we felt the performance of this version of software in this situation was not good enough,” Vogt wrote in his blog post. “We took the proactive step of notifying NHTSA that we would be filing a voluntary recall of previous versions of our software that were impacted by the issue.”
The CEO said such voluntary recalls will probably become “commonplace.”
“We believe this is one of the great benefits of autonomous vehicles compared to human drivers; our entire fleet of AVs is able to rapidly improve, and we are able to carefully monitor that progress over time,” he said.
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