How bridges are rated
The 0-9 inspection scale, the components inspectors grade, and how Good/Fair/Poor is decided
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
Every inventoried highway bridge in the country gets graded the same way. A certified inspector rates three separate components, each on a 0 to 9 scale:
- The deck - the surface you drive on (NBI item 58).
- The superstructure - the beams, girders, or trusses that carry the deck (item 59).
- The substructure - the piers, columns, and abutments that hold everything up (item 60).
Culverts, which are essentially large buried structures carrying a road over water, get a single combined rating (item 62) instead.
The bridge's overall condition is set by its lowest component rating. FHWA's rule is simple: lowest rating 7 or higher is Good, 5 or 6 is Fair, 4 or lower is Poor. One bad component is enough; a bridge with a pristine deck and a substructure rated 4 is a poor bridge.
The full scale
| Rating | FHWA description | Condition class |
|---|---|---|
| 9 | Excellent condition | Good |
| 8 | Very good condition | Good |
| 7 | Good condition | Good |
| 6 | Satisfactory condition | Fair |
| 5 | Fair condition | Fair |
| 4 | Poor condition | Poor |
| 3 | Serious condition | Poor |
| 2 | Critical condition | Poor |
| 1 | Imminent failure condition | Poor |
| 0 | Failed condition, out of service | Poor |
Applied to the whole 2025 inventory, that rule sorts the country's 624,169 bridges into 272,775 good (43.7%), 309,717 fair (49.6%), and 41,677 poor (6.7%).
Source: FHWA Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation's Bridges and the National Bridge Inventory.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.