Or. Rev. Stat. § 381.660 – Use of tolls to pay bonded indebtedness and bridge maintenance

(1) Tolls shall be fixed, charged and collected for passage over the bridge mentioned in ORS 381.605, and shall be so fixed and adjusted as to provide a fund sufficient to pay the principal and interest of the bonds issued for such bridge and an additional fund to pay the cost of maintaining, repairing and operating such bridge.
(2) The tolls, except such part thereof as may be necessary to pay the cost of maintaining, repairing and operating the bridge, shall be placed in a special fund, which is pledged to and charged with the payment of the bonds and the interest thereon.