U.S. safety regulators are investigating reports that autonomous robotaxis operated by General Motors Cruise may stop too quickly or stop moving unexpectedly, potentially stranded passengers.
Three reported rear-end collisions after Cruise’s self-driving cars slammed on the brakes have sparked an investigation, according to the National Highway Traffic Safety Administration. At the time, robotaxis were staffed with human safety drivers.
The agency also has multiple reports that Cruise robotaxis without a human safety driver became immobile in San Francisco traffic, potentially stranded passengers and blocking lanes.
In an investigative document posted on its website Friday, NHTSA said the report of the vehicle’s inability to move came from discussions with Cruise, media reports and local authorities.
According to the National Highway Traffic Safety Administration (NHTSA) accident database, there have been two reports of injuries related to emergency braking, including a serious injury to a cyclist last March.
NHTSA said it will determine how often the problems occur and the potential safety concerns they cause. The investigation, which covers about 242 Cruise self-driving cars, could lead to a recall. “With this data in hand, NHTSA can address safety concerns involving these technologies through further investigation and enforcement,” the agency said in a statement.
Cruise spokesman Drew Pusateri said the company is cooperating with the investigation and that its vehicles have driven nearly 700,000 miles autonomously in complex cities without life-threatening injuries.
“This is happening against the backdrop of more than 40,000 fatalities on American roads each year,” he wrote. “There is always a balance between healthy regulatory scrutiny and our urgent need for life-saving innovations.”
In none of the crashes, police issued a ticket, and in each case, the self-driving car was responding to aggressive or erratic behavior by other road users, he said. “AVs are working to minimize the severity of the collision and the risk of injury,” Pusateri wrote.
During the traffic jam, Pusateri wrote that whenever Cruise technology wasn’t very confident about moving, it was designed to be conservative, turning on its hazard lights and coming to a safe stop.
“If required, Cruise personnel will be dispatched to retrieve the vehicle as quickly as possible,” Pusateri wrote. Such shutdowns were rare and did not result in any accidents, he wrote.
NHTSA said Cruise reported three rear-end collisions under a 2021 order requiring self-driving car companies to notify the agency of the accidents.
Reports of Cruise robo-taxis becoming immobile in traffic came from the San Francisco City Department of Transportation and the San Francisco County Department of Transportation, the agency said.

Cruise vehicles may trap passengers in unsafe places, such as carriageways or intersections, increasing the risk of disembarking passengers. And they can become an obstacle for other road users, causing them to make unsafe maneuvers to avoid collisions. “These vehicles may also obstruct the path of emergency response vehicles, thereby delaying their emergency response time and presenting a secondary safety risk,” NHTSA said in the document.
Beginning in May, the city began noticing 911 calls from people inconvenienced by Cruise operations, the city’s transportation agency said in comments to NHTSA. Some city police officers also saw Cruise vehicles immobilized in traffic lanes. One incident in June involved 13 Cruise vehicles parked on a major road. Two other major blockages were reported in August, the agency said.
The survey comes at an important time for Cruise, which began charging self-driving passengers in San Francisco in June without a human safety driver. It’s also a pivotal time for the self-driving car industry, with Google spinoff Waymo operating a robo-taxi service in the Phoenix area and planning to expand to San Francisco. Other companies are also moving to services without human safety drivers.
San Francisco-based Cruise plans to expand the service to Phoenix and Austin, Texas. The GM-owned startup has been testing self-driving Chevrolet Bolt electric vehicles for years.