Washington Revised Code Title 81. Transportation § 81.28.190. Unreasonable preferences and prejudices prohibited

A common carrier subject to regulation by the commission as to rates and service shall not make or give any undue or unreasonable preference or advantage to any person, corporation, locality, or particular description of traffic in any respect whatsoever, or subject any particular person, corporation, locality, or particular description of traffic, to any undue or unreasonable prejudice or disadvantage in any respect whatsoever.