Washington Revised Code Title 46. Motor Vehicles § 46.44.030. Maximum lengths

(2)(a) It is unlawful for any person to operate upon the public highways of this state any combination consisting of a tractor and semitrailer that has a semitrailer length in excess of fifty-three feet or a combination consisting of a tractor and two trailers in which the combined length of the trailers exceeds sixty-one feet, with or without load.

(b) The restriction under this subsection does not apply to two trailers or semitrailers with a total weight that does not exceed twenty-six thousand pounds and when the two trailers or semitrailers do not carry property but constitute inventory property of a manufacturer, distributor, or dealer of such trailers. The total combination under this subsection (2)(b) may not exceed eighty-two feet of overall length.

(4)(a) The length limitations under this section do not apply to vehicles transporting poles, pipe, machinery, or other objects of a structural nature that cannot be dismembered and operated by a public utility when required for emergency repair of public service facilities or properties, but in respect to night transportation every such vehicle and load thereon shall be equipped with a sufficient number of clearance lamps on both sides and marker lamps upon the extreme ends of any projecting load to clearly mark the dimensions of the load.

(b) Excluded from the calculation of length under this section are certain devices that provide added safety, energy conservation, or are otherwise necessary, and are not designed or used to carry cargo. The length-exclusive devices must be identified in rules adopted by the department of transportation under RCW 46.44.101.