By Ken Thomas, Associated Press

July 15, 2008

WASHINGTON (AP) -- President Bush's top highway safety official is stepping down after leading the administration's work on auto safety and vehicle fuel economy standards for two years.

Nicole Nason, the administrator of the National Highway Traffic Safety Administration, told colleagues Tuesday that she plans to leave the agency in August.

That's according to a source familiar with her plans who requested anonymity because her decision hasn't been announced by the Transportation Department.

Nason, who has led NHTSA since May 2006, has focused on promoting child passenger safety and advanced safety technology during her tenure.

She helped develop upgraded fuel economy standards that responded to an energy law requiring new cars and trucks to reach a fleetwide average of at least 35 miles per gallon by 2020.