How bridge inspections work
Who inspects bridges, how often, and where the data goes
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
The numbers on this site exist because of a federal inspection system created after the 1967 Silver Bridge collapse killed 46 people. The National Bridge Inspection Standards (NBIS) require every public highway bridge longer than 20 feet to be inspected by certified inspectors on a fixed cycle.
- Routine inspections happen at least every 24 months for most bridges. Under the current standards, owners can qualify certain low-risk bridges for longer intervals, and bridges in worse shape are inspected more often.
- Underwater inspections of submerged foundations run on their own cycle, generally at least every 60 months.
- Damage and special inspections follow floods, impacts, and other events.
Inspection results flow from bridge owners to state DOTs to FHWA's National Bridge Inventory, which is published annually and is the source for every page on this site. The practical consequence: the ratings you see here are at most about two years old for almost every bridge, and the inventory vintage is stated on every page.
Source: National Bridge Inspection Standards, 23 CFR 650 subpart C · FHWA NBI.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.