RCW 46.44.020

It is unlawful for any vehicle unladen or with load to exceed a height of fourteen feet above the level surface upon which the vehicle stands. This height limitation does not apply to authorized emergency vehicles or repair equipment of a public utility engaged in reasonably necessary operation. The provisions of this section do not relieve the owner or operator of a vehicle or combination of vehicles from the exercise of due care in determining that sufficient vertical clearance is provided upon the public highways where the vehicle or combination of vehicles is being operated; and no liability may attach to the state or to any county, city, town, or other political subdivision by reason of any damage or injury to persons or property by reason of the existence of any structure over or across any public highway where the vertical clearance above the roadway is fourteen feet or more; or, where the vertical clearance is less than fourteen feet, if impaired clearance signs of a design approved by the state department of transportation are erected and maintained on the right side of any such public highway in accordance with the manual of uniform traffic control devices for streets and highways as adopted by the state department of transportation under chapter 47.36 RCW. If any structure over or across any public highway is not owned by the state or by a county, city, town, or other political subdivision, it is the duty of the owner thereof when billed therefor to reimburse the state department of transportation or the county, city, town, or other political subdivision having jurisdiction over the highway for the actual cost of erecting and maintaining the impaired clearance signs, but no liability may attach to the owner by reason of any damage or injury to persons or property caused by impaired vertical clearance above the roadway.