"Truck-tractor" shall mean any vehicle designed and intended primarily for drawing other vehicles and not so constructed as to carry a load other than a part of the vehicle and load so drawn, except that a truck-tractor engaged in the transportation of automobiles may transport motor vehicles on a part of the power unit.
RSA 259:116
RSA 259:1, XXVIII-a. 1967, 341:1. 1981, 146:1. 1983, 434:5, eff. June 24, 1983.