The National Highway Traffic Admin. says Administrator Nicole Nason is leaving the organization after a 2-year stint, vacating a position that could take some time to fill.

Nason, 37, has held the top position since May 2006 when she replaced Jeffrey Runge, who left the post in July 2005. She was appointed by President Bush, which leaves open the possibility a successor may not be named until the next White House administration is in place.

Nason, who is credited with promoting safety technology and helping craft a controversial proposal mandating a 4.5% annual fuel-economy increase on new cars and trucks, will leave NHTSA in August, the Associated Press reports.

Also during her tenure, NHTSA put into law a requirement that auto makers install anti-rollover technology on all new vehicles by 2012.

Additionally, Nason is credited with requiring head protection for side-impact crashes and recently led the effort to update the agency’s consumer crash-test program for new cars and trucks.