The U.S. National Highway Traffic Safety Administration (NHTSA) concluded an investigation into 258 Zoox vehicles due to a braking problem, which resulted in two rear-end collisions causing injuries to motorcyclists. The probe was initiated in response to the incidents, prompting Zoox to recall the vehicles and update their software to prevent sudden braking near bicyclists or motorcyclists. Following a review of Zoox's data, the NHTSA's Office of Defects Investigation closed the probe.