Wash. Rev. Code § 81.53.030
Whenever a railroad company desires to cross a highway or railroad at grade, it shall file a written petition with the commission setting forth the reasons why the crossing cannot be made either above or below grade. Whenever the legislative authority of a county, or the municipal authorities of a city, or the state officers authorized to lay out and construct state roads, or the state parks and recreation commission, desire to extend a highway across a railroad at grade, they shall file a written petition with the commission, setting forth the reasons why the crossing cannot be made either above or below grade. Upon receiving the petition, the commission shall immediately investigate it, giving at least ten days' notice to the railroad company and the county or city affected thereby, of the time and place of the investigation, to the end that all parties interested may be present and heard. If the highway involved is a state road or parkway, the secretary of transportation or the state parks and recreation commission shall be notified of the time and place of hearing. The evidence introduced shall be reduced to writing and be filed by the commission. If it finds that it is not practicable to cross the railroad or highway either above or below grade, the commission shall enter a written order in the cause, either granting or denying the right to construct a grade crossing at the point in question. The commission may provide in the order authorizing a grade crossing, or at any subsequent time, that the railroad company shall install and maintain proper signals, warnings, flaggers, interlocking devices, or other devices or means to secure the safety of the public and its employees. In respect to existing railroad grade crossings over highways the construction of which grade crossings was accomplished other than under a commission order authorizing it, the commission may in any event require the railroad company to install and maintain, at or near each crossing, on both sides of it, a sign known as the sawbuck crossing sign with the lettering "Railroad Crossing" inscribed thereon with a suitable inscription indicating the number of tracks. The sign shall be of standard design conforming to specifications furnished by the Washington state department of transportation.
RCW 81.53.030