Any funds required to repay such bonds, or the interest thereon when due, shall be taken from that portion of the motor vehicle fund which results from the imposition of excise taxes on motor vehicle and special fuels and which is distributed to the transportation improvement account in the motor vehicle fund under RCW
46.68.090(2)(f) and vehicle-related fees in the motor vehicle fund, and shall never constitute a charge against any allocations of any other such funds in the motor vehicle fund to the state, counties, cities, and towns unless and until the amount of the motor vehicle fund arising from vehicle-related fees and the excise tax on motor vehicle and special fuels and distributed to the transportation improvement account proves insufficient to meet the requirements for bond retirement or interest on any such bonds.