Oregon Revised Statutes Highways, Roads, Bridges and Ferries § 381.245

If any bridge constructed, purchased or otherwise acquired under ORS 381.205 to 381.305 is operated as a toll bridge, and the revenues or any part thereof derived as a result of the tolls and charges collected have been pledged and revenue bonds issued, in fixing and determining the amount of tolls to be charged consideration shall be given, among other things, to the amount necessary to be received to pay the interest upon the revenue bonds and to provide for the retirement of the principal of the bonds. Provisions shall be made for the application of the revenue so received to the payment of the interest and principal of the revenue bonds as their respective payments become due.