SDCL § 31-7-3: Cooperation with federal highway administration in location and construction of interstate highways.

The department, in cooperation with the Federal Highway Administration of the United States Department of Transportation, or other agencies of the United States government, may locate and construct the South Dakota sections of the National System of Interstate Highways according to American Association of State Highway and Transportation Officials Standards peculiar to that system and shall operate and maintain the highways as toll-free facilities.