Sts. & Hy. Code, § 31223

The authority may also carry insurance or indemnity bonds insuring against the loss of tolls or other revenues to be derived from the toll tunnel by reason of any interruption in the use of the toll tunnel from any cause whatever. The proceeds of the insurance or indemnity bonds shall be paid into the fund into which the tolls and other revenues of the toll tunnel so insured are required to be paid and shall be applied to the same purposes and in the same manner as other money in the fund. The insurance or indemnity bonds may be in an amount equal to the probable tolls and other revenues to be received from the operation of the toll tunnel during any period of time determined by the authority and fixed in its discretion, and may be paid for out of the toll revenue fund as specified in the proceedings.