Wash. Rev. Code § 47.36.280
The department of transportation shall, by January 1, 1992, adopt minimum pavement marking standards for the area designating the limits of the vehicle driving lane along the right edge for arterials that do not have curbs or sidewalks and are inside urbanized areas. In preparing the standards, the department of transportation shall take into consideration all types of pavement markings, including flat, raised, and recessed markings, and their effect on pedestrians, bicycle, and motor vehicle safety.
The standards shall provide that a jurisdiction shall conform to these requirements, at such time thereafter that it undertakes to (1) renew or install permanent markings on the existing or new roadway, and (2) remove existing nonconforming raised pavement markers at the time the jurisdiction prepares to resurface the roadway, or earlier, at its option. These standards shall be in effect, as provided in this section, unless the legislative authority of the local governmental body finds that special circumstances exist affecting vehicle and pedestrian safety that warrant a variance to the standard.
For the purposes of this section, "urbanized area" means an area designated as such by the United States bureau of census and having a population of more than fifty thousand. Other jurisdictions that install pavement marking material on the right edge of the roadway shall do so in a manner not in conflict with the minimum state standard.
RCW 47.36.280