Wash. Rev. Code § 47.24.040
All funds accruing to the credit of incorporated cities and towns in the motor vehicle fund shall be paid monthly to such incorporated cities and towns and shall, by the respective cities and towns, be placed in a fund to be designated as "city street fund" and disbursed as authorized and directed by the legislative authority of the city or town, as agents of the state, for salaries and wages, material, supplies, equipment, purchase or condemnation of right-of-way, engineering or any other proper highway or street purpose in connection with the construction, alteration, repair, improvement or maintenance of any city street or bridge, or viaduct or underpassage along, upon or across such streets. Such expenditure may be made either independently or in conjunction with any federal, state or any county funds.
RCW 47.24.040