Travelers are stuck in a traffic jam as people hit the road before the busy Thanksgiving Day weekend in Chicago, Illinois
Travelers are stuck in a traffic jam as people hit the road before the busy Thanksgiving Day weekend in Chicago, Illinois, U.S., November 21, 2017.

The top U.S. auto safety regulator is stepping down to return to the California Air Resources Board, the National Highway Traffic Safety Administration said on Friday.

Steven Cliff has overseen the agency's safety investigations into Tesla as well as efforts to shrink sharply higher traffic deaths and significantly boost vehicle fuel economy requirements.

He was named NHTSA's deputy administrator in February 2021 but had been running the agency on an acting basis. In October President Joe Biden nominated him to be administrator and he was confirmed in the role in May by the U.S. Senate.

Cliff is a former deputy executive officer at CARB and will become executive officer at CARB effective Sept. 12. He was the first Senate-confirmed NHTSA administrator since January 2017.

Transportation Secretary Pete Buttigieg said NHTSA's chief counsel, Ann Carlson, will assume Cliff's duties when he departs. Carlson was previously co-director of UCLA Law's Emmett Institute on Climate Change and the Environment.

Cliff said in a statement he was honored to work with agency staff "on a series of measures that will make vehicles more fuel efficient and safer for all Americans."

NHTSA in March sharply boosted fuel efficiency requirements through 2026, reversing former President Donald Trump's rollback of U.S. regulations aimed at improving gas mileage and cutting tailpipe pollution. Under Cliff, NHTSA also reinstated a sharp increase in penalties for automakers whose vehicles do not meet fuel efficiency requirements.

In May, NHTSA said U.S. traffic deaths jumped 10.5% in 2021 to 42,915, marking the highest number killed on American roads in a single year since 2005 and the highest reported since the agency began using its current traffic fatality tracking system in 1975. Cliff said the figures confirm "we have a deadly crisis on our nation's roads."


In June, NHTSA upgraded its investigation into 830,000 Tesla vehicles with Autopilot involving crashes into parked emergency vehicles.

Cliff told Reuters in July he wanted to complete the defect investigation into Tesla's Autopilot "as quickly as we possibly can but I also want to get it right. There's a lot of information that we need to comb through."

Since 2016, NHTSA has opened 38 special investigations of crashes involving Tesla vehicles where advanced driver assistance systems were suspected of being used.

The agency has increased investigations into various safety issues involving Tesla and the automaker agreed to a rising number of recalls.