The commission shall, in the granting of certificates to operate any private, nonprofit transportation provider, 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 vehicle used or to be used in transporting persons for compensation. The commission shall fix the amount of the insurance policy or policies or surety bond, giving due consideration to the character and amount of traffic, the number of persons affected, and the degree of danger which the proposed operation involves. Such liability and property damage insurance or surety bond shall be maintained in force on each vehicle while so used. Each policy for liability of property damage insurance or surety bond required herein, shall be filed with the commission and kept in full force and effect, and failure to do so shall be cause for the revocation of the certificate.