(1) Where State or other Federal agency MUTCDs or Supplements are required, they shall be in substantial conformance with the national MUTCD. Substantial conformance means that the State MUTCD or Supplement shall conform as a minimum to the Standard statements included in the national MUTCD. The FHWA Division Administrators and Associate Administrator for the Federal Lands Highway Program may grant exceptions in cases where a State MUTCD or Supplement cannot conform to Standard statements in the national MUTCD because of the requirements of a specific State law that was in effect prior to January 16, 2007, provided that the Division Administrator or Associate Administrator determines based on information available and documentation received from the State that the non-conformance does not create a safety concern. The Guidance statements contained in the national MUTCD shall also be in the State MUTCD or Supplement unless the reason for not including it is satisfactorily explained based on engineering judgment, specific conflicting State law, or a documented engineering study. A State MUTCD or Supplement shall not contain Standard, Guidance, or Option statements that contravene or negate Standard or Guidance statements in the national MUTCD. In addition to a State MUTCD or Supplement, supplemental documents that a State issues, including but not limited to policies, directives, standard drawings or details, and specifications, shall not contravene or negate Standard or Guidance statements in the national MUTCD. The FHWA Division Administrators shall approve the State MUTCDs and Supplements that are in substantial conformance as defined heretofore with the national MUTCD. The FHWA Associate Administrator of the Federal Lands Highway Program shall approve other Federal land management agencies' MUTCDs and Supplements that are in substantial conformance as defined heretofore with the national MUTCD. The FHWA Division Administrators and the FHWA Associate Administrators for the Federal Lands Highway Program have the flexibility to determine on a case-by-case basis the degree of variation allowed in a State MUTCD or Supplement to accommodate existing State laws as described heretofore, for the express purpose of amending such laws over time.

(2) States and other Federal agencies are encouraged to adopt the National MUTCD in its entirety as their official Manual on Uniform Traffic Control Devices.

(3) States and other Federal agencies shall adopt changes issued by the FHWA to the National MUTCD within two years from the effective date of the final rule. For those States that automatically adopt the MUTCD immediately upon the effective date of the latest edition or revision of the MUTCD, the FHWA Division Administrators have the flexibility to allow these States to install certain devices from existing inventory or previously approved construction plans that comply with the previous MUTCD during the two-year adoption period.

(1) Existing highways. Each State, in cooperation with its political subdivisions, and Federal agency shall have a program as required by 23 U.S.C. 402(a), which shall include provisions for the systematic upgrading of substandard traffic control devices and for the installation of needed devices to achieve conformity with the MUTCD. The FHWA may establish target dates of achieving compliance with changes to specific devices in the MUTCD.

(2) New or reconstructed highways. Federal-aid projects for the construction, reconstruction, resurfacing, restoration, or rehabilitation of streets and highways shall not be opened to the public for unrestricted use until all appropriate traffic control devices, either temporary or permanent, are installed and functioning properly. Both temporary and permanent devices shall conform to the MUTCD.

(3) Construction area activities. All traffic control devices installed in construction areas using Federal-aid funds shall conform to the MUTCD. Traffic control plans for handling traffic and pedestrians in construction zones and for protection of workers shall conform to the requirements of 23 CFR part 630, subpart J, Traffic Safety in Highway and Street Work Zones.