23 C.F.R. § 470 app A to Subpart A of Part 470
Section 103(c)(4)(A) and (B), of title 23, U.S.C., permits States to request the designation of National Highway System routes as parts or future parts of the Interstate System. The FHWA Administrator may approve such a request if the route is a logical addition or connection to the Interstate System and has been, or will be, constructed to meet Interstate standards. The following are the general criteria to be used to evaluate 23 U.S.C. 103(c) requests for Interstate System designations.
1. The proposed route should be of sufficient length to serve long-distance Interstate travel, such as connecting routes between principal metropolitan cities or industrial centers important to national defense and economic development.
2. The proposed route should not duplicate other Interstate routes. It should serve Interstate traffic movement not provided by another Interstate route.
3. The proposed route should directly serve major highway traffic generators. The term "major highway traffic generator" means either an urbanized area with a population over 100,000 or a similar major concentrated land use activity that produces and attracts long-distance Interstate and statewide travel of persons and goods. Typical examples of similar major concentrated land use activities would include a principal industrial complex, government center, military installation, or transportation terminal.
4. The proposed route should connect to the Interstate System at each end, with the exception of Interstate routes that connect with continental routes at an international border, or terminate in a "major highway traffic generator" that is not served by another Interstate route. In the latter case, the terminus of the Interstate route should connect to routes of the National Highway System that will adequately handle the traffic. The proposed route also must be functionally classified as a principal arterial and be a part of the National Highway System system.
5. The proposed route must meet all the current geometric and safety standards criteria as set forth in 23 CFR part 625 for highways on the Interstate System, or a formal agreement to construct the route to such standards within 25 years must be executed between the State(s) and the Federal Highway Administration. Any proposed exceptions to the standards shall be approved at the time of designation.
6. A route being proposed for designation under 23 U.S.C. 103(c)(4)(B) must have an approved final environmental document (including, if required, a 49 U.S.C. 303(c) [Section 4(f)] approval) covering the route and project action must be ready to proceed with design at the time of designation. Routes constructed to Interstate standards are not necessarily logical additions to the Interstate System unless they clearly meet all of the above criteria.
23 C.F.R. § 470 app A to Subpart A of Part 470