Wash. Rev. Code § 47.14.040
The department or the county, city, or town to which the right-of-way is donated shall, upon request, grant the donor an airspace lease or a permit for the purpose of erecting or maintaining, or both, one or more signs advertising a business of the donor that is conducted on premises adjacent to the donated parcel unless the sign or signs would be detrimental to the safety and operation of the highway, road, or street. This provision applies to all highways, roads, and streets other than limited access highways and streets, where it applies only until the donated parcel becomes part of a completed operating facility. Except as provided in this section, any such sign shall conform to the requirements of all other applicable federal, state, and local laws and ordinances. The lease agreement or permit shall take into consideration applicable county and city zoning ordinances and may provide for compensation for removal of the sign in accordance with applicable federal, state, and local laws and ordinances. The lease agreement or permit shall specify the conditions for signage.
RCW 47.14.040