49 CFR 523.6 - Heavy-duty vehicle.
(a) A heavy-duty vehicle is any commercial medium- and heavy-duty on highway vehicle or a work truck, as defined in 49 U.S.C. 32901(a)(7) and (19). For the purpose of this part, heavy-duty vehicles are divided into three regulatory categories as follows:
(2) Heavy-duty vocational vehicles; and
(3) Truck tractors with a GVWR above 26,000 pounds.
(b) The heavy-duty vehicle classification does not include:
(1) Vehicles defined as medium duty passenger vehicles.
(2) Vehicles excluded from the definition of “heavy-duty vehicle” because of vehicle weight or weight rating (such as light duty vehicles as defined in § 523.5).
(3) Vehicles excluded from the definition of motor vehicle in 40 CFR 85.1703.