NHTSA opens investigation into Amazon's Zoox self-driving vehicles over unexpected braking resulting in two rear-end collisions; 500 vehicles with automated Zoox systems under probe

The U.S. National Highway Traffic Safety Administration (NHTSA) said on Monday it has opened an investigation into Amazon.com's self-driving Zoox vehicles due to unexpected braking leading to two rear-end collisions that injured motorcyclists.

The NHTSA said it had opened its preliminary evaluation after two crashes involving the self-driving technology unit's vehicles equipped with the Zoox Automated Driving System that resulted in minor injuries to motorcyclists and started a probe into 500 Zoox vehicles with automated driving systems.

Each incident involved a Toyota Highlander equipped with the Zoox automated driving system.

A Zoox spokesperson said the company was reviewing the request for information but did not offer in a statement additional details on the incidents. "Transparency and collaboration with regulators is of the utmost importance, and we remain committed to working closely with NHTSA to answer their questions," the statement said.

In March, Zoox said it was expanding its vehicle testing in California and Nevada to include a wider area, higher speeds and nighttime driving, as it competes with Alphabet's Waymo robotaxis. Amazon acquired Zoox in 2020 for $1.3 billion.

NHTSA said both crashes occurred during daytime lighting conditions and within the operational design limits of the Zoox system. NHTSA said its initial investigation confirmed "each of the Zoox vehicles was operating with the ADS engaged in the moments leading up to each collision."

The investigation will evaluate the Zoox Automated Driving System performance particularly relating to the collisions as well as "the behavior in crosswalks around vulnerable road users, and in other similar rear-end collision scenarios."

NHTSA in March 2023 opened a probe into the self-certification by Zoox in 2022 of a robotaxi without traditional driving controls.