Code of Federal Regulations Title 23. Highways § 23.810.102 Eligible projects

(a) Construction of exclusive or preferential high occupancy vehicle, truck, or emergency vehicle lanes, except the construction of exclusive or preferential lanes limited to use by emergency vehicles can be approved only on the Federal-aid Interstate System;

(b) Highway traffic control devices;

(c) Passenger loading areas and facilities (including shelters) that are on or serve a Federal-aid system;  and

(d) Construction or designation of fringe and transportation corridor parking facilities. For parking facilities located in the central business district the Federal-aid project must be limited to space reserved exclusively for the parking of high occupancy vehicles used for carpools or vanpools.