Congress’ investigative arm says a plan to relocate thousands of Defense Department workers by 2011 will significantly increase traffic congestion in the Washington area, notably around the Bethesda National Naval Medical Center and the Fort Belvoir Army base in Fairfax County.

A report from the Government Accountability Office projects that immediate costs to deal with traffic problems created by the 2005 Base Realignment and Closure plan would be at least $2 billion nationwide.