Wash. Rev. Code § 81.80.130
To the extent allowed under 49 U.S.C. Sec. 14501, the commission shall: Supervise and regulate every common carrier in this state; make, fix, alter, and amend, just, fair, reasonable, minimum, maximum, or minimum and maximum, rates, charges, classifications, rules, and regulations for all common carriers; regulate the accounts, service, and safety of operations thereof; require the filing of reports and other data thereby; and supervise and regulate all common carriers in all other matters affecting their relationship with competing carriers of every kind and the shipping and general public. The commission may by order approve rates filed by common carriers in respect to certain designated commodities and services when, in the opinion of the commission, it is impractical for the commission to make, fix, or prescribe rates covering the commodities and services.
RCW 81.80.130