County profile · official public datasets

Bonneville County, ID

213 public highway bridges tracked in the FHWA National Bridge Inventory: 30.5% rated Good, 66.7% Fair, 2.8% Poor.

213
Public bridges: 30.5%
Good condition: 2.8%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Bonneville County posts a top-quartile lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 25%
lowest Poor share in state: 2.8%
Poor-condition share: 213
public highway bridges: 1977
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.

Bonneville County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Bonneville County ranks #11 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 2.8%). Bonneville County, Idaho contains 213 public highway bridges. Roughly 30.5% are rated “Good,” 66.7% “Fair,” and 2.8% “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.

Total bridges

213

Public highway bridges in Bonneville County

Good condition

30.5%

65 of 213 rated 7-9

Fair condition

66.7%

142 of 213 rated 5-6

Poor condition

2.8%

6 of 213 rated 4 or below

In-state Poor-share rank

#11 of 44

Among Idaho counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 213 NBI-tracked bridges by lowest applicable component rating.

Good

30.5% (65)

Fair

66.7% (142)

Poor

2.8% (6)

Bonneville County's Poor-condition bridges carry 47,720 vehicle crossings a day

That is 3.7% of the county's reported daily bridge traffic on 2.8% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 7,953 crossings a day against 5,147 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 213 of 213 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

54.9% of Bonneville County's bridges have passed the 50-year mark

117 of the 213 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 30.5% 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 53.4% of the county's Poor-condition bridge traffic

S 25 E; S HITT RD over SAND CREEK, built 1994, carries 25,500 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 6-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 47,720 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

3
1930s

5
1940s

7
1950s

30
1960s

54
1970s

33
1980s

17
1990s

13
2000s

25
2010s

20
2020s

6

What this shows Construction peaked in the 1960s, when 54 of the county's bridges still in the inventory were built, which is 25.4% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1977) matches the Idaho average (1979).

How Bonneville County compares with Idaho's closest counties by inventory size

The 5 Idaho counties nearest Bonneville County in number of bridges, with their condition splits. Its 2.8% Poor share is the 1st-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1977 is in line with the group.

Showing the 5 closest of 43 Idaho counties eligible for comparison.

Bridge inventory size and condition shares for Bonneville County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Bingham County	263	17.1%	79.5%	3.4%	1975
Shoshone County	260	21.5%	68.8%	9.6%	1971
Idaho County	215	37.2%	56.7%	6%	1975
Bonneville County (this page)	213	30.5%	66.7%	2.8%	1977
Kootenai County	154	31.2%	65.6%	3.2%	1984
Valley County	149	45%	48.3%	6.7%	1982

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 Bonneville 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 Bonneville County, both outside Idaho so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside ID (213 bridges here).

Floyd County, IA · 213 bridges
Calhoun County, MI · 213 bridges
Alcorn County, MS · 213 bridges
Calhoun County, MS · 213 bridges

Similar average build year

Nearest mean year-built outside ID (1977 here).

San Diego County, CA · avg 1977 · 1,632 bridges
King County, WA · avg 1977 · 1,238 bridges
Riverside County, CA · avg 1977 · 1,117 bridges
Shelby County, TN · avg 1977 · 1,077 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 213 Good 65 Fair 142 Poor 6

Fair-condition bridges (142)

Sort:

Bonneville County Bridge Snapshot

Condition distribution

Bonneville County's Poor-condition bridges carry 47,720 vehicle crossings a day

54.9% of Bonneville County's bridges have passed the 50-year mark

One structure carries 53.4% of the county's Poor-condition bridge traffic

How Bonneville County compares with Idaho's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Fair-condition bridges (142)

JACKKNIFE ROAD

W 113 N

I 15 NBL

I 15 SBL

SH 31

OSGOOD ROAD

PAYNE ROAD

NHS 6710;YORK RD

US 20

STP7046;LINCOLN RD

SOFTBALL DRIVE

S7286;JOHN ADAMS P

US 20 WBL

E 81ST N

US 20 EBL & WBL

US 20 WBL

US 20

US 20

US 20 EBL

STC6731;W 145 N

BRENTWOOD DRIVE

US 26

US 20

US 26

STC 7146;GARFIELD

US 20 EBL

US 20 WBL

SMA7406;PANCHERI

US 26

STC6859;E RIRIE HY

STC6859;E RIRIE HY

US 20 EBL & RAMP

NHS8031;OLD BUTTE

US 20 WBL

US 26

MILLIGAN ROAD

US 26

SMA 7406;PANCHERI

PARK RD; TAUTPHAUS

I 15B ;BROADWAY ST

SH 43

STP 7446;SUNNYSIDE

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