Wash. Rev. Code § 81.53.420
The utilities and transportation commission shall adopt rules to implement the provisions of RCW 81.53.400 and 81.53.410 pursuant to chapter 34.05 RCW. The commission shall invite the participation of all interested parties in any hearings or proceedings taken under this section, including any parties who request notice of any proceedings.
Any rules adopted under this section and any devices employed under RCW 81.53.410 shall conform to the national standards established by the current manual, including any future revisions, on the Uniform Traffic Control Devices as approved by the American national standards institute as adopted by the federal highway administrator of the United States department of transportation.
Rules adopted by the commission shall specifically prescribe the duties, procedures, and equipment to be used by the flagpersons required by RCW 81.53.410.
RCW 81.53.400 through 81.53.420 and rules adopted thereunder shall be enforced by the commission under the provisions of chapter 81.04 RCW: PROVIDED, That rules adopted by the commission shall recognize that cities with a population in excess of four hundred thousand are responsible for specific public thoroughfares and have the specific responsibility and authority for determining the practices relating to safeguarding the public during construction, repair, and maintenance activities.
RCW 81.53.420