23 U.S.C. § 103 — National Highway System

(a) In General. For this title, the Federal-aid highway system is the National Highway System, and it includes the Interstate System. (b) National Highway System. (1) Description. The National Highway System is made of highway routes and connections to transportation facilities that (A) serve major population centers, international border crossings, ports, airports, public transportation, other transportation hubs, and other major destinations; (B) meet national defense needs; and (C) serve travel and commerce between and within regions and states. (2) Components. The National Highway System is made up of: (A) the system shown on the map the Secretary of Transportation sent Congress with the 1996 "Pulling Together" report, plus changes the Secretary approved before the MAP-21 law; (B) other major urban and rural roads, and border crossings on them, added since MAP-21; (C) other connector highways, including toll roads, added since MAP-21, that link National Highway System routes to a major transportation hub; (D) a strategic highway network — a set of highways important to national defense policy, giving defense access and emergency movement capability in peace and war, not previously on the system — which may include Interstate or non-Interstate highways and which the Secretary designates with federal agencies and the states; and (E) major connectors linking key military bases to the strategic highway network, also designated by the Secretary with federal agencies and the states. (3) Modifications to NHS. (A) The Secretary may change the National Highway System — including adding a connector to a major hub, or removing a road — if a state proposes the change and the Secretary finds it meets the system's legal standards, and either improves the system's national transportation value, or, for a removal, is reasonable and fitting. (B) In proposing a change, a state must work with local and regional officials; in urbanized areas, local officials act through the area's metropolitan planning organization. (c) Interstate System. (1) Description. (A) The Dwight D. Eisenhower National System of Interstate and Defense Highways, including in D.C. and Puerto Rico, consists of highways designed, located, and chosen under this paragraph. (B) Design. Interstate highways must meet the design standards in section 109(b), except that highways in Alaska and Puerto Rico only need standards adequate for current and likely future traffic and local needs. (C) Location. Interstate routes must be placed to (i) connect major metro areas, cities, and industrial centers as directly as practical; (ii) serve national defense; and (iii) connect, where practical, with important routes in Canada and Mexico at suitable border points. (D) Selection of routes. States and their neighboring states jointly select each Interstate route, working with local and regional officials, subject to the Secretary's approval. (2) Maximum mileage. The Interstate System cannot exceed 43,000 miles, not counting mileage designated under paragraph (4). (3) Modifications. The Secretary may approve or require Interstate System changes consistent with this subsection's policies. (4) Interstate system designations. (A) Additions. If the Secretary finds a National Highway System road meets all Interstate standards and is a logical addition, the Secretary may designate it as an Interstate route, if the state or states involved recommend it. (B) Future Interstate System routes. (i) If the Secretary finds a National Highway System road would logically extend the Interstate System and would qualify once it met Interstate standards, the Secretary may designate it a "future Interstate System route," if the state or states recommend it. (ii) This designation requires the state's written promise to build the road to full Interstate standards within 25 years of the agreement. (iii) If the state hasn't substantially finished construction by that deadline, the Secretary must remove the future-route designation. (iv) Removing that designation doesn't stop the Secretary from later designating the road an actual Interstate route another way. (v) Agreements made before August 10, 2005 are treated as including this same 25-year limit, no matter what earlier completion date the agreement listed. (vi) No law, rule, map, or document from any government may refer to, and no such road may be signed or marked as, an actual Interstate System highway until it (I) is built to full Interstate design and construction standards, and (II) is formally designated an Interstate route. (C) Financial responsibility. Except as this title otherwise provides, designating a road under this paragraph creates no extra federal funding responsibility for it. (5) Exemption of interstate system. (A) In general. Except as (B) provides, the Interstate System is not treated as a historic site under section 303 of title 49 or section 138 of this title, even if all or part of it is listed, or eligible to be listed, on the National Register of Historic Places. (B) Individual elements. Subject to (C): (i) the Secretary must identify, through the process used to exempt the Interstate System under section 306108 of title 54, which specific parts of the Interstate System have major or exceptional historic significance (like a historic bridge or a highly significant engineering feature); and (ii) those specific parts are treated as historic sites under section 303 of title 49 or section 138 of this title, as applicable. (C) Construction, maintenance, restoration, and rehabilitation activities. (B) does not stop a state from building, maintaining, preserving, restoring, or rehabilitating a historically significant part of the Interstate System, as long as the state follows section 303 of title 49 or section 138 of this title, and section 306108 of title 54, as applicable.