Cal. Sts. & High. Code § 31169

The bond redemption and interest payments constitute a first direct and exclusive charge and lien on all tolls and other revenues, and interest thereon, and sinking funds created therefrom received from the use and operation of the toll tunnel. Such tolls and revenues together with the interest earned thereon constitute a trust fund for the security and payment of the bonds and shall not be used or pledged for any other purpose as long as any such bonds are outstanding and unpaid.