Wash. Rev. Code § 81.68.060
In granting certificates to operate any auto transportation company, for transporting for compensation persons and their baggage on the vehicles of auto transportation companies carrying passengers, the commission shall require the owner or operator to first procure liability and property damage insurance from a company licensed to make liability insurance in the state of Washington or a surety bond of a company licensed to write surety bonds in the state of Washington on each motor-propelled vehicle used or to be used in transporting persons for compensation, in an amount of no less than one hundred thousand dollars for any recovery for personal injury by one person, no less than three hundred thousand dollars for any vehicle having a capacity of sixteen passengers or less, no less than five hundred thousand dollars for any vehicle having a capacity of seventeen passengers or more for all persons receiving personal injury by reason of at least one act of negligence, and no less than fifty thousand dollars for damage to property of any person other than the insured. The commission shall fix the amount of the insurance policy or policies or security deposit by giving due consideration to the character and amount of traffic, the number of persons affected, and the degree of danger that the proposed operation involves. The liability and property damage insurance or surety bond must be maintained in force on the motor-propelled vehicle while in use, and each policy for liability or property damage insurance or surety bond required by this section must be filed with the commission and kept in full force and effect. Failure to file and maintain the required insurance is cause for the revocation of the certificate.
RCW 81.68.060