The US transportation safety regulator has launched a preliminary investigation into a Waymo autonomous vehicle that failed to stop for a school bus in Atlanta, Georgia, on September 22. The incident involved the vehicle passing a stopped bus with flashing lights and deployed stop arm, raising safety concerns. No safety operator was present, and Waymo has committed to software improvements. The investigation covers about 2,000 Waymo vehicles and follows multiple prior reviews of the company's self-driving systems.