The term “automobile transporter” means any vehicle combination designed and used for the transport of assembled highway vehicles, including truck camper units. An automobile transporter shall not be prohibited from the transport of cargo or general freight on a backhaul, so long as it complies with weight limitations for a truck tractor and semitrailer combination.

The term “maxi-cube vehicle” means a truck tractor combined with a semitrailer and a separable property-carrying unit designed to be loaded and unloaded through the semitrailer, with the length of the separable property-carrying unit being not more than 34 feet and the length of the vehicle combination being not more than 65 feet.

The term “driveaway saddlemount vehicle transporter combination” means a vehicle combination designed and specifically used to tow up to 3 trucks or truck tractors, each connected by a saddle to the frame or fifth-wheel of the forward vehicle of the truck or truck tractor in front of it. Such combination may include one fullmount.

The term “backhaul” means the return trip of a vehicle transporting cargo or general freight, especially when carrying goods back over all or part of the same route.

The term “trailer transporter towing unit” means a power unit that is not used to carry property when operating in a towaway trailer transporter combination.

A length limitation prescribed or enforced by a State under paragraph (1)(A) of this subsection applies only to a semitrailer or trailer and not to a truck tractor.

If the chief executive officer of a State, after consulting under paragraph (2) of this subsection, decides a segment of the Dwight D. Eisenhower System of Interstate and Defense Highways is not capable of safely accommodating a commercial motor vehicle having a length described in subsection (b)(1)(A) of this section or the motor vehicle combination described in subsection (c) of this section, the chief executive officer may notify the Secretary of that decision and request the Secretary to exempt that segment from either or both provisions.

Before making a decision under paragraph (1) of this subsection, the chief executive officer shall consult with units of local government in the State in which the segment of the Dwight D. Eisenhower System of Interstate and Defense Highways is located and with the chief executive officer of any adjacent State that may be directly affected by the exemption. As part of the consultations, consideration shall be given to any potential alternative route that serves the area in which the segment is located and can safely accommodate a commercial motor vehicle having a length described in subsection (b)(1)(A) of this section or the motor vehicle combination described in subsection (c) of this section.

A chief executive officer’s notification under this subsection must include specific evidence of safety problems supporting the officer’s decision and the results of consultations about alternative routes.