1. Federal-aid highways. The national system of interstate and defense highways, the federal-aid primary highway system. Highway status as of July 1, 1984 Princeton University Public content 1984. U.S.G.S. United States. Federal Highway Administration. Department of Transportation United States. Geological Survey North Decimal Degree 71.50000... [Reston, Va.] : U.S. Geological Survey, 1984.