Idaho bridge conditions
4,646 inventoried bridges · 250 rated poor · county by county
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- 250 of Idaho's 4,646 inventoried bridges are rated in poor condition (5.4%) in the 2025 National Bridge Inventory, as of .
- 1,468 bridges (31.6%) are rated good and 2,928 (63.0%) fair.
- The national poor rate is about 6.7%; Idaho is at or below it (see all states ranked).
- The busiest poor-rated bridge in the state is I 90 Wbl over Pedestrian/bike Path in Kootenai County, carrying about 31,250 vehicles a day.
By the measure that matters most - the most traffic on a poor rating - it is I 90 Wbl over Pedestrian/bike Path in Kootenai County, built 1971, carrying about 31,250 vehicles a day. That is a repair-priority flag, not a collapse warning: what a poor rating does and does not mean. See the worst bridge in every state.
Good 31.6% · Fair 63.0% · Poor 5.4% of 4,646 bridges
Bridge conditions by county
Sorted by the number of poor-rated bridges. Click any county for its full bridge list.
| County | Bridges | Rated poor | Poor % |
|---|---|---|---|
| Shoshone County | 261 | 26 | 10.0% |
| Idaho County | 216 | 15 | 6.9% |
| Custer County | 126 | 14 | 11.1% |
| Lincoln County | 53 | 14 | 26.4% |
| Bonner County | 104 | 11 | 10.6% |
| Boundary County | 84 | 11 | 13.1% |
| Valley County | 153 | 10 | 6.5% |
| Jerome County | 111 | 10 | 9.0% |
| Bingham County | 263 | 9 | 3.4% |
| Lemhi County | 114 | 9 | 7.9% |
| Elmore County | 98 | 8 | 8.2% |
| Fremont County | 138 | 8 | 5.8% |
| Adams County | 87 | 8 | 9.2% |
| Kootenai County | 159 | 7 | 4.4% |
| Camas County | 62 | 7 | 11.3% |
| Bannock County | 128 | 6 | 4.7% |
| Clearwater County | 88 | 6 | 6.8% |
| Canyon County | 291 | 6 | 2.1% |
| Clark County | 39 | 5 | 12.8% |
| Boise County | 89 | 5 | 5.6% |
| Gooding County | 80 | 5 | 6.2% |
| Twin Falls County | 126 | 5 | 4.0% |
| Owyhee County | 49 | 4 | 8.2% |
| Jefferson County | 125 | 4 | 3.2% |
| Blaine County | 96 | 4 | 4.2% |
| Washington County | 80 | 4 | 5.0% |
| Bonneville County | 213 | 3 | 1.4% |
| Benewah County | 48 | 3 | 6.2% |
| Nez Perce County | 72 | 3 | 4.2% |
| Ada County | 302 | 3 | 1.0% |
| Gem County | 57 | 3 | 5.3% |
| Payette County | 65 | 3 | 4.6% |
| Caribou County | 45 | 2 | 4.4% |
| Teton County | 37 | 2 | 5.4% |
| Franklin County | 23 | 2 | 8.7% |
| Minidoka County | 67 | 1 | 1.5% |
| Power County | 71 | 1 | 1.4% |
| Latah County | 119 | 1 | 0.8% |
| Lewis County | 21 | 1 | 4.8% |
| Butte County | 32 | 1 | 3.1% |
| Cassia County | 117 | 0 | 0.0% |
| Oneida County | 23 | 0 | 0.0% |
| Madison County | 80 | 0 | 0.0% |
| Bear Lake County | 34 | 0 | 0.0% |
The 25 busiest poor-rated bridges in Idaho
Frequently asked questions
How many bridges in Idaho are in poor condition?
250 of Idaho's 4,646 inventoried highway bridges are rated in poor condition (5.4%) in the 2025 National Bridge Inventory. 'Poor' is FHWA's classification for a bridge whose deck, superstructure, or substructure is rated 4 or lower on the 0-9 scale; it was formerly called 'structurally deficient'.
Are the poor-rated bridges in Idaho safe to drive on?
A poor rating flags advanced deterioration that needs repair or close monitoring; it does not by itself mean a bridge is unsafe. Bridges judged unsafe are closed or restricted to lighter loads by the owner. Inspections continue on all open bridges, generally at least every 24 months under the National Bridge Inspection Standards.
Source: FHWA National Bridge Inventory, 2025 vintage, reported by the Idaho DOT.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.