Federal government asks Zoox to send more information about autonomous vehicles that suddenly brake

US federal regulators have requested more information from Zoox, Amazon’s self-driving unit, as part of an investigation into rear-end collision risks posed by unexpected braking.

The National Highway Traffic Safety Administration (NHTSA) opened a preliminary investigation into Zoox on May 10 after receiving two reports of Zoox vehicles braking unexpectedly, resulting in rear-end collisions with motorcyclists that resulted in minor injuries. Zoox has a permit from the California Department of Motor Vehicles to test its driverless safety vehicles in Foster City and parts of San Francisco.

On Thursday, the agency gave Zoox a deadline of July 12 to send more information to help with its investigation. The letter details a list of 13 requests for information, including the number of kilometers traveled on public roads with self-driving software engaged by geographic region; the number of AV-controlled hard braking events with and without on-board human supervision; a list and summary of braking incidents; a detailed timeline of events starting 30 seconds before each incident; and copies of videos, graphical renderings of measured trajectories and planned paths for each road user and other data beginning 30 seconds before each incident.

NHTSA has already confirmed, through an initial investigation into both incidents, that each of Zoox’s Toyota Highlanders was operating with the company’s autonomous vehicle software enabled in the moments leading up to the collisions.

In a letter from NHTSA’s Office of Defects Investigation (ODI) dated May 30, the agency said that in both reported incidents, Zoox vehicles braked in response to another road user who did not was not directly in front of them.

“ODI is concerned that vehicles exhibiting unexpected rapid braking may increase the risk of a crash, property damage and injury,” the letter reads. “The risk is particularly serious for road users behind Zoox vehicles who are unable to reasonably anticipate or react to unexpected hard braking.”

The investigation will evaluate the performance of Zoox’s automated driving system, as well as its behavior in pedestrian crossings around vulnerable road users and in other similar rear-end collision scenarios.

Both incidents that prompted this investigation involved motorcyclists, who often closely followed cars and divided lanes. NHTSA’s action in this case could be a sign of increased scrutiny of autonomous vehicle makers after GM Cruise lost its operating permits in California after withholding information about an incident that led to the crash of a Cruise robo-taxi and the dragging of a pedestrian for 20 feet.

The federal government is also investigating Alphabet’s Waymo after receiving a total of 31 reports of unexpected movements of its robotaxis that led to accidents and potentially violated traffic safety laws.