How Bridge Inspections Work
The federal bridge inspection program, who inspects, how often, what they check, and how inspection data becomes the NBI records on PlainBridges.
On this register · 2024 NBI
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Inspectors submit the records this site ranks. The 2024 file covers 623,216 public highway bridges; 6.8% are Poor. Iowa leads the 49-jurisdiction share table at 19.16%; Nevada sits at 1.14%.
- 623,216
- Inventoried bridges
- 6.8%
- Poor nationwide
- 19.16%
- Iowa · highest share
- 1.14%
- Nevada · lowest share
Routine intervals are commonly 24 months; qualifying bridges can be inspected more or less often under current NBIS rules.
Who does the inspecting
State departments of transportation and other responsible bridge owners conduct inspections using qualified personnel, under standards set by the National Bridge Inspection Standards (NBIS). Federal rules define the risk-based inspection intervals, inspector qualifications, and the annual reporting framework that feeds the NBI. FHWA compiles the submitted records nationally; it does not send its own inspectors to individual bridges.
How often inspections happen
A 24-month routine interval is the common baseline, but qualifying bridges can have shorter intervals, some are on 12-month or more frequent enhanced schedules when condition concerns warrant closer attention, or longer approved extended intervals when a bridge consistently rates well and meets the NBIS criteria for extension. The interval is set per-bridge, not applied uniformly across a state.
What inspectors check
Inspectors rate the deck, superstructure, and substructure separately on the 0-9 NBI condition scale, plus channel condition for waterway crossings and scour-critical status where a foundation could be undermined by moving water. Culverts receive a single combined rating instead of the three-part split. The lowest of the rated elements determines the overall Good/Fair/Poor category shown on PlainBridges.
From inspection to NBI record
Each state DOT compiles its inspected bridges into an annual submission to FHWA under the NBI reporting requirements. FHWA validates and consolidates the 50-state file into the National Bridge Inventory, the same federal dataset PlainBridges builds its condition pages, rankings, and search tool from. The scale of that submission varies enormously by state, Texas alone tracks 56,729 bridges in the current file.
States with the largest inspection programs
Top 8 states by total tracked bridges, 2024 NBI file.
What to do with this
The inspection interval is set per bridge, not per state, checking your own bridge's record is the only way to know its actual schedule.
- Texas tracks the largest inspection program in the file at 56,729 bridges, see how its inspection scale compares to condition outcomes. Texas bridge data
- The 0-9 element rating produced by each inspection determines Good/Fair/Poor, not a fixed schedule alone. How safety ratings work
- Look up a specific bridge to see its most recent inspection-derived condition record. Search bridges
Inspection intervals and program scale are current NBIS rules and the 2024 NBI file; the exact schedule for any individual bridge is set by its responsible owner.
Sources: Federal Highway Administration (FHWA) National Bridge Inventory.
Last updated: April 2026
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.