Bonds issued under the authority of RCW
47.60.800 through
47.60.808 shall distinctly state that they are a general obligation of the state of Washington, shall pledge the full faith and credit of the state to the payment of the principal thereof and the interest thereon, and shall contain an unconditional promise to pay such principal and interest as the same shall become due. The principal and interest shall be first payable in the manner provided in RCW
47.60.800 through
47.60.808 from the proceeds of the state excise taxes on motor vehicle and special fuels imposed by chapters *82.36 and
82.38 RCW and distributed to the state pursuant to RCW
46.68.130 and shall never constitute a charge against any allocations of such funds to counties, cities, and towns unless and until the amount of the motor vehicle fund arising from the excise taxes on motor vehicle and special fuels and available for state highway purposes proves insufficient to meet the requirements for bond retirement or interest on any such bonds. Proceeds of such excise taxes are hereby pledged to the payment of any bonds and the interest thereon issued under the authority of RCW
47.60.800 through
47.60.808, and the legislature agrees to continue to impose these excise taxes on motor vehicle and special fuels in amounts sufficient to pay, when due, the principal and interest on all bonds issued under the authority of RCW
47.60.800 through
47.60.808.