Except as otherwise provided in this section and except for tow trucks with vehicles in tow, a State may allow the operation of LCV's on the Interstate System only as listed in appendix C to this part.

Except as otherwise provided in this section, a State may not allow the operation on the NN of any CMV combination with two or more cargo-carrying units (not including the truck tractor) whose cargo-carrying units exceed:

The maximum combination trailer, semitrailer, or other type of length limitation authorized by State law or regulation of that State on or before June 1, 1991; or

The length of the cargo-carrying units of those CMV combinations, by specific configuration, in actual, lawful operation on a regular or periodic basis (including continuing seasonal operation) in that State on or before June 1, 1991, as listed in appendix C to this part.

Notwithstanding paragraph (a)(2) of this section, the following CMV combinations with two or more cargo-carrying units may operate on the NN.

Truck tractor-semitrailer-trailer and truck tractor-semitrailer-semitrailer combinations with a maximum length of the individual cargo units of 28.5 feet or less.

Vehicles described in § 658.13(e) and (g).

Truck-trailer and truck-semitrailer combinations with an overall length of 65 feet or less.

Maxi-cubes.

Tow trucks with vehicles in tow.

For specific safety purposes and road construction, a State may make minor adjustments of a temporary and emergency nature to route designation and vehicle operating restrictions applicable to combinations subject to 23 U.S.C. 127(d) and 49 U.S.C. 31112 and in effect on June 1, 1991 (July 6, 1991, for Alaska). Minor adjustments which last 30 days or less may be made without notifying the FHWA. Minor adjustments which exceed 30 days require approval of the FHWA. When such adjustments are needed, a State must submit to the FHWA, by the end of the 30th day, a written description of the emergency, the date on which it began, and the date on which it is expected to conclude. If the adjustment involves alternate route designations, the State shall describe the new route on which vehicles otherwise subject to the freeze imposed by 23 U.S.C. 127(d) and 49 U.S.C. 31112 are allowed to operate. To the extent possible, the geometric and pavement design characteristics of the alternate route should be equivalent to those of the highway section which is temporarily unavailable. If the adjustment involves vehicle operating restrictions, the State shall list the restrictions that have been removed or modified. If the adjustment is approved, the FHWA will publish the notice of adjustment, with an expiration date, in the Federal Register. Requests for extension of time beyond the originally established conclusion date shall be subject to the same approval and publications process as the original request. If upon consultation with the FHWA a decision is reached that minor adjustments made by a State are not legitimately attributable to road or bridge construction or safety, the FHWA will inform the State, and the original conditions of the freeze must be reimposed immediately. Failure to do so may subject the State to a penalty pursuant to 23 U.S.C. 141.

A State may issue a permit authorizing a CMV to transport an overlength nondivisible load on two or more cargo-carrying units on the NN without regard to the restrictions in § 658.23(a)(2).

States further restricting or prohibiting the operation of vehicles subject to 23 U.S.C. 127(d) and 49 U.S.C. 31112 after June 1, 1991, shall notify the FHWA within 30 days after the restriction is effective. The FHWA will publish the restriction in the Federal Register as an amendment to appendix C to this part. Failure to provide such notification may subject the State to a penalty pursuant to 23 U.S.C. 141.

The Federal Highway Administrator, on his or her own motion or upon a request by any person (including a State), shall review the information set forth in appendix C to this part. If the Administrator determines there is cause to believe that a mistake was made in the accuracy of the information contained in appendix C to this part, the Administrator shall commence a proceeding to determine whether the information published should be corrected. If the Administrator determines that there is a mistake in the accuracy of the information contained in appendix C to this part, the Administrator shall publish in the Federal Register the appropriate corrections to reflect that determination.