49 CFR 393.1: Scope of the rules in this part.

(a) The rules in this part establish minimum standards for commercial motor vehicles as defined in § 390.5 of this title. Only motor vehicles (as defined in § 390.5) and combinations of motor vehicles which meet the definition of a commercial motor vehicle are subject to the requirements of this part. All requirements that refer to motor vehicles with a GVWR below 4,536 kg (10,001 pounds) are applicable only when the motor vehicle or combination of motor vehicles meets the definition of a commercial motor vehicle.

(b)(1) Every motor carrier and its employees must be knowledgeable of and comply with the requirements and specifications of this part.

(2) Every intermodal equipment provider and its employees or agents responsible for the inspection, repair, and maintenance of intermodal equipment interchanged to motor carriers must be knowledgeable of and comply with the applicable requirements and specifications of this part.

(c) No motor carrier may operate a commercial motor vehicle, or cause or permit such vehicle to be operated, unless it is equipped in accordance with the requirements and specifications of this part.

(d) No intermodal equipment provider may operate intermodal equipment, or cause or permit such equipment to be operated, unless it is equipped in accordance with the requirements and specifications of this part.

(e) The rules in this part do not apply to “pipeline welding trucks” as defined in 49 CFR 390.38(b).