California Code, Streets and Highways Code - SHC § 31122

The authority in establishing toll charges shall give consideration to the cost of operating and maintaining the toll tunnel, including the cost of insurance, and to the amount required annually to meet the redemption of bonds and interest payments thereon. At all times the tolls and charges shall be fixed at rates to yield annual revenue equal to annual operating and maintenance expenses, including insurance costs, and all redemption payments and interest charges of the bonds issued for the toll tunnel as they fall due.