RCW 46.44.036: Combination of units—Limitation.

Except as provided in RCW 46.44.037 , it is unlawful for any person to operate upon the public highways of this state any combination of vehicles consisting of more than two vehicles. For the purposes of this section a truck tractor-semitrailer or pole trailer combination will be considered as two vehicles but the addition of another axle to the tractor of a truck tractor-semitrailer or pole trailer combination in such a way that it supports a proportional share of the load of the semitrailer or pole trailer shall not be deemed a separate vehicle but shall be considered a part of the truck tractor. For the purposes of this section a converter gear used in converting a semitrailer to a full trailer shall not be deemed a separate vehicle but shall be considered a part of the trailer.