Total bridges
88
Public highway bridges in Boise County
County profile · official public datasets
Boise County, ID
88 public highway bridges tracked in the FHWA National Bridge Inventory: 46.6% rated Good, 47.7% Fair, 5.7% Poor.
- 88
- Public bridges
- 46.6%
- Good condition
- 5.7%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Boise County posts a higher-than-median Poor-condition share among rated counties in the state across rated county bridge inventory.
- 25th
- of 44 on Poor share
- 5.7%
- Poor-condition share
- 88
- public highway bridges
- 1978
- avg year built
Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.
Boise County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Boise County ranks #25 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 5.7%). Boise County, Idaho contains 88 public highway bridges. Roughly 46.6% are rated “Good,” 47.7% “Fair,” and 5.7% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.
Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.
Source: FHWA National Bridge Inventory. See methodology for full definitions.
Good condition
46.6%
41 of 88 rated 7-9
Fair condition
47.7%
42 of 88 rated 5-6
Poor condition
5.7%
5 of 88 rated 4 or below
In-state Poor-share rank
#25 of 44
Among Idaho counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 88 NBI-tracked bridges by lowest applicable component rating.
Good 46.6% (41)
Fair 47.7% (42)
Poor 5.7% (5)
Boise County's Poor-condition bridges carry 220 vehicle crossings a day
That is 0.2% of the county's reported daily bridge traffic on 5.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 44 crossings a day against 1,069 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.
Computed over the 88 of 88 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
46.6% of Boise County's bridges have passed the 50-year mark
41 of the 88 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 46.6% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.
Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.
One structure carries 45.5% of the county's Poor-condition bridge traffic
ANDERSON CREEK RD over ANDERSON CREEK, built 1983, carries 100 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 5-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 220 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Boise County's bridges were built
88 bridges with a recorded construction year, grouped by decade
- 1910s 1
1910–1919
1 bridges
- 1920s 1
1920–1929
1 bridges
- 1930s 3
1930–1939
3 bridges
- 1940s 3
1940–1949
3 bridges
- 1950s
1950–1959
10 bridges
- 1960s
1960–1969
13 bridges
- 1970s
1970–1979
14 bridges
- 1980s
1980–1989
13 bridges
- 1990s
1990–1999
15 bridges
- 2000s
2000–2009
7 bridges
- 2010s
2010–2019
6 bridges
- 2020s 2
2020–2029
2 bridges
What this shows Construction peaked in the 1990s, when 15 of the county's bridges still in the inventory were built, which is 17% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year (1978) matches the Idaho average (1979).
How Boise County compares with Idaho's closest counties by inventory size
The 5 Idaho counties nearest Boise County in number of bridges, with their condition splits. Its 5.7% Poor share is the 3rd-lowest of these 6. Its average build year of 1978 against a peer-group mean of 1975 is in line with the group.
Showing the 5 closest of 43 Idaho counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Blaine County | 96 | 25% | 71.9% | 3.1% | 1978 |
| Clearwater County | 88 | 43.2% | 51.1% | 5.7% | 1973 |
| Boise County (this page) | 88 | 46.6% | 47.7% | 5.7% | 1978 |
| Adams County | 87 | 32.2% | 57.5% | 10.3% | 1975 |
| Boundary County | 83 | 32.5% | 57.8% | 9.6% | 1982 |
| Gooding County | 80 | 16.3% | 76.3% | 7.5% | 1965 |
Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Boise County's. Source: FHWA National Bridge Inventory, 2024 release.
Nationwide counties with similar inventory size or average build year
Two NBI-derived peer sets for Boise County, both outside Idaho so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside ID (88 bridges here).
- Chicot County, AR · 88 bridges
- Prairie County, AR · 88 bridges
- Grand County, CO · 88 bridges
- Spalding County, GA · 88 bridges
Similar average build year
Nearest mean year-built outside ID (1978 here).
- Orange County, CA · avg 1978 · 1,164 bridges
- Sumner County, KS · avg 1978 · 659 bridges
- Allen County, IN · avg 1978 · 613 bridges
- Livingston County, IL · avg 1978 · 579 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Poor-condition bridges (5)
AVELENE CK. ROAD
PoorOver: GRIMES CREEK
9 MI SW OF IDAHO CITY, Boise, ID
Built 1954 Load: 9.1 t ADT: 20
SHAFER CREEK ROAD
PoorOver: SHAFER CREEK
3.2S 1.4E HORSESHOE BEND, Boise, ID
Built 1914 Load: 10.9 t ADT: 20
COTTONWD-BANNOCK
PoorOver: MORES CREEK
1 MI ESE OF IDAHO CITY, Boise, ID
Built 1962 Load: 20.7 t ADT: 30
BOULDER CREEK ROAD
PoorOver: MORES CREEK
5 MI NE IDAHO CITY, Boise, ID
Built 1982 Load: 24.0 t ADT: 50
ANDERSON CREEK RD
PoorOver: ANDERSON CREEK
0.2 E. 0.1 S. CROUCH, Boise, ID
Built 1983 Load: 52.6 t ADT: 100
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
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.