WASHINGTON (Reuters) -The National Highway Traffic Safety Administration said on Monday it has opened a preliminary investigation into about 2,000 Waymo self-driving vehicles after reports that the company's robotaxis may have failed to follow traffic safety laws around a stopped school bus. NHTSA opened the investigation after a recent media report aired video of an incident in Georgia in which a Waymo did not remain stationary when approaching a school bus with its red lights flashing and stop arm deployed. Waymo's automated driving system surpassed 100 million miles of driving in July and is logging 2 million miles per week, the agency said.