Wash. Rev. Code § 81.80.020
The business of operating as a motor carrier of freight for compensation along the highways of this state is declared to be a business affected with a public interest. The rapid increase of motor carrier freight traffic and the fact that under the existing law many motor trucks are not effectively regulated have increased the dangers and hazards on public highways and make it imperative that regulation to the fullest extent allowed under 49 U.S.C. Sec. 14501 should be employed to the end that the highways may be rendered safer for the use of the general public; that the wear of such highways may be reduced; that congestion on highways may be minimized; that the shippers of the state may be provided with a stabilized service and rate structure; that sound economic conditions in such transportation and among such carriers may be fostered in the public interest; that adequate, economical, and efficient service by motor carriers, and reasonable charges therefor, without unjust discrimination, undue preferences or advantages, or unfair or destructive competitive practices may be promoted; that the common carriage of commodities by motor carrier may be preserved in the public interest; that the relations between, and transportation by and regulation of, motor carriers and other carriers may be improved and coordinated so that the highways of the state of Washington may be properly developed and preserved, and the public may be assured adequate, complete, dependable, and stable transportation service in all its phases.
RCW 81.80.020