23 U.S.C. § 318

Federal highway funds shall not be used for the reconstruction or relocation of any highway giving access to an airport constructed or extended after December 20, 1944, or for the reconstruction or relocation of any highway which has been or may be closed or the usefulness of which has been may be impaired by the location or construction of any airport constructed or extended after December 20, 1944, unless, prior to such construction or extension, as the case may be, the State transportation department and the Secretary have concurred with the officials in charge of the airport that the location of such airport or extension thereof and the consequent reconstruction or relocation of the highway are in the public interest.