49 U.S.C. § 47127

(a) General Authority .— To improve the airport and airway system of the United States consistent with regional airport system plans financed under section 13(b) of the Airport and Airway Development Act of 1970, the Secretary of Transportation may carry out ground transportation demonstration projects to improve ground access to air carrier airport terminals. The Secretary may carry out a demonstration project independently or by grant or contract, including an agreement with another department, agency, or instrumentality of the United States Government. (b) Priority .— In carrying out this section, the Secretary shall give priority to a demonstration project that— (1) affects an airport in an area with an operating regional rapid transit system with existing facilities reasonably near the airport; (2) includes connection of the airport terminal to that system; (3) is consistent with and supports a regional airport system plan adopted by the planning agency for the region and submitted to the Secretary; and (4) improves access to air transportation for individuals residing or working in the region by encouraging the optimal balance of use of airports in the region.