The U.S. National Highway Traffic Safety Administration (NHTSA) has initiated a preliminary investigation into approximately 2,000 of Alphabet's Waymo self-driving vehicles. The probe follows reports that the company's robotaxis may have failed to properly adhere to traffic safety laws concerning a stopped school bus. The incident in question reportedly involved a Waymo vehicle maneuvering around a school bus that had its red lights flashing and stop arm extended while students were disembarking. NHTSA's investigation will scrutinize how Waymo's autonomous driving technology interacts with traffic control devices and avoids collisions with stationary and semi-stationary objects. This is the latest instance of regulatory examination of self-driving systems. Waymo has stated that safety is a top priority and that it has already implemented software improvements related to stopping for school buses, with further updates planned. The company noted that in the specific incident, the bus's signals were not visible from the vehicle's angle of approach.