ORS § 381.230
The construction, purchase, acquisition, operation or maintenance of any bridge or of its approaches authorized by ORS 381.205 to 381.314 may be financed in whole or in part through the issuance and sale of revenue bonds. As security for the payment of the bonds, the total or any part of the revenues from any such bridge may be hypothecated and pledged by the governing authorities purchasing, constructing, operating or maintaining the bridge without the necessity of the electors of the political subdivisions authorizing the same. However, no such hypothecation or pledge of revenues, or the issuance of the revenue bonds shall constitute in any manner, or to any extent be made to constitute, a general obligation of any county, city, town or port making the pledge.
ORS 381.230