N.Y. Veh. & Traf. Law § 151-a

§ 151-a. Tractor. A motor vehicle designed and used as the power unit\nin combination with a semitrailer or trailer, or two such trailers in\ntandem. Any such motor vehicle shall not carry cargo except that a\ntractor and semitrailer engaged in the transportation of automobiles may\ntransport motor vehicles on part of the power unit.\n