Tool · Decode
Bridge condition decoder
Enter the NBI element ratings from any bridge record and see, in plain English, how the FHWA classifies it — and exactly what would make it structurally deficient.
According to the Federal Highway Administration (FHWA), more than 575,000 public highway bridges are inspected and scored under the National Bridge Inventory, with each structure re-rated on a fixed cycle as of the 2024 NBI release. This decoder applies the same federal rules to the numbers you enter. For the full scoring rubric, see our methodology.
How the NBI condition scale works
FHWA inspectors rate each major element — deck, superstructure, and substructure — on a 0–9 scale where 9 is excellent and 0 is failed. The overall condition category comes from the lowest of those element ratings: 7–9 is Good, 5–6 is Fair, 3–4 is Poor, and 0–2 is Critical. A bridge is classified structurally deficient when any of those components is rated 4 or below, or when its composite sufficiency rating falls under 50.
What does the decoder tell me?
Does structurally deficient mean unsafe?
No. It is a maintenance and funding flag. Deficient bridges stay open under inspection, often with load posting, until repair or replacement is funded.
Why does the worst element decide the category?
A bridge is only as sound as its weakest load-carrying component, so FHWA derives the overall condition from the lowest element rating rather than an average.
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| Publisher | Kiznis Studio |
| Sources | FHWA National Bridge Inventory, public U.S. government datasets |