Bridge Performance Measures
The bridge condition performance measures established by FHWA for State DOT’s requires that bridges on the National Highway System (NHS) be rated according to the National Bridge Inventory (NBI) condition ratings for deck, superstructure, substructure, and culverts. Based on the lowest rating of these items, a bridge receives a rating of good, fair, or poor. If the lowest rating is greater than or equal to 7, the bridge is classified as “Good”; if it is less than or equal to 4, the bridge is classified as “Poor”. Bridges rated below 7 but above 4 are classified as “Fair”.
Of the 6,800 on-system bridges, roughly 3,200 are NHS bridges and are evaluated and reported on annually. At its peak, Oklahoma reported 1,168 of its 6,800 highway bridges as structurally deficient in 2004. Since then, an aggressive attack was launched with the implementation of the Rebuilding Oklahoma Access and Driver Safety (ROADS) fund to reduce these numbers. As a result, with the plan currently in place the number of Oklahoma’s structurally deficient bridges stand at 132, an 89% drop since 2004. Bridges that receive a structurally deficient rating do not meet the minimum standards for condition and load-bearing capacity. In addition, they may experience significant deterioration of the deck, superstructure, and/or substructure elements. The rating assigned to these bridges are as described above.