23 CFR 657.13: Certification requirement.

Each State shall certify to the Federal Highway Administrator, before January 1 of each year, that it is enforcing all State laws respecting maximum vehicle size and weight permitted on what, prior to October 1, 1991, were the Federal-aid Primary, Secondary, and Urban Systems, including the Interstate System, in accordance with 23 U.S.C. 127. The States must also certify that they are enforcing and complying with the ISTEA freeze on the use of LCV's and other multi-unit vehicles. The certification shall be supported by information on activities and results achieved during the preceding 12-month period ending on September 30 of each year.