NBI Rating Scale (0-9)

What It Means

The NBI rating scale is a 10-point ordinal scale (0 through 9) used consistently across all primary bridge components in the National Bridge Inventory: 9 (Excellent Condition, new or like-new), 8 (Very Good, no problems noted), 7 (Good, some minor problems), 6 (Satisfactory, structural elements show some minor deterioration), 5 (Fair, all primary structural elements are sound but may have minor section loss, cracking, spalling, or scour), 4 (Poor, advanced section loss, deterioration, spalling, or scour, this is the threshold for structurally deficient), 3 (Serious, loss of section, deterioration, spalling, or scour have seriously affected primary structural components, local failures are possible), 2 (Critical Condition, advanced deterioration, bridge may need to be closed until corrective action is taken), 1 (Imminent Failure, major deterioration or section loss, bridge is closed to traffic but corrective action may put it back in light service), and 0 (Failed Condition, out of service and beyond corrective action). Ratings 7-9 indicate a bridge in Good condition under current FHWA performance measures, ratings 5-6 indicate Fair condition, and ratings 4 and below indicate Poor condition (structurally deficient). The scale was originally developed in the 1970s following the Silver Bridge collapse on the Ohio River in 1967 that killed 46 people and prompted Congress to create the National Bridge Inspection Standards in 1971. Inspectors must be certified as Team Leaders under NBIS requirements and complete FHWA-approved training. Consistency across inspectors is supported by photo reference guides, team leader oversight, and periodic quality assurance reviews by state DOTs and FHWA Division offices.

Frequently Asked Questions