Stephen Ridella, who had served as director of the National Highway Traffic Safety Administration's (NHTSA) Office of Defects Investigation since 2017, oversaw key investigations including a probe into Tesla Autopilot and whether 67 million ARC Automotive Inc air bag inflators were defective.
He said on LinkedIn he had left NHTSA to join Zoox.
Another NHTSA official, Anne Collins, who was associate administrator for enforcement, opted to retire on April 30.
Last week, President Joe Biden withdrew the nomination of NHTSA's chief counsel Ann Carlson to take the agency's top job on a permanent basis.
NHTSA declined to comment when asked about the specific personnel moves but said it "believes it is well positioned to continue to address safety and enforcement efforts. We have a highly professional team in place and believe our enforcement and investigative work will remain strong and effective."
Six safety groups on Tuesday including the Governors Highway Safety Association urged Biden to quickly name a new NHTSA administrator nominee, citing rising traffic deaths.
Carlson had been named acting head of NHTSA in September and was formally nominated for the top position in March. The agency has ongoing safety probes into Tesla, air bag ruptures and is working on efforts to reduce traffic deaths and new regulations to boost vehicle fuel economy requirements.
Carlson said it was her decision to withdraw her nomination. For much of the last six years, NHTSA has been without a Senate-confirmed administrator.
A government audit report released last week said NHTSA routinely fails to meet its internal timelines for completing auto safety defect investigations, saying it hindering its ability to quickly respond to severe safety risks.
(Reporting by David Shepardson; Editing by Tom Hogue and Chris Reese)
By David Shepardson
