County profile · official public datasets

Caribou County, ID

45 public highway bridges tracked in the FHWA National Bridge Inventory: 26.7% rated Good, 66.7% Fair, 6.7% Poor.

45
Public bridges: 26.7%
Good condition: 6.7%
Poor condition

The verdict

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

Caribou County pairs a higher-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

31st
of 44 on Poor share: 6.7%
Poor-condition share: 45
public highway bridges: 1985
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.

Caribou County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Caribou County ranks #31 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.7%). Caribou County, Idaho contains 45 public highway bridges. Roughly 26.7% are rated “Good,” 66.7% “Fair,” and 6.7% “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.

Total bridges

Public highway bridges in Caribou County

Good condition

26.7%

12 of 45 rated 7-9

Fair condition

66.7%

30 of 45 rated 5-6

Poor condition

6.7%

3 of 45 rated 4 or below

In-state Poor-share rank

#31 of 44

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

Condition distribution

Share of 45 NBI-tracked bridges by lowest applicable component rating.

Good

26.7% (12)

Fair

66.7% (30)

Poor

6.7% (3)

Caribou County's Poor-condition bridges carry 205 vehicle crossings a day

That is 0.9% of the county's reported daily bridge traffic on 6.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 68 crossings a day against 355 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 45 of 45 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

28.9% of Caribou County's bridges have passed the 50-year mark

13 of the 45 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 26.7% 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 48.8% of the county's Poor-condition bridge traffic

8 MILE ROAD over BEAR RIVER, built 1972, 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 3-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 205 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1950s

2
1960s

4
1970s

15
1980s

10
1990s

2
2000s

7
2010s

4
2020s

1

What this shows Construction peaked in the 1970s, when 15 of the county's bridges still in the inventory were built, which is 33.3% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1985, 6 years newer than the Idaho average of 1979.

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

The 5 Idaho counties nearest Caribou County in number of bridges, with their condition splits. Its 6.7% Poor share is the 3rd-lowest of these 6. Its average build year of 1985 against a peer-group mean of 1979 is 6 years newer.

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

Bridge inventory size and condition shares for Caribou County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Lincoln County	53	18.9%	58.5%	22.6%	1973
Owyhee County	48	31.3%	60.4%	8.3%	1975
Benewah County	47	21.3%	74.5%	4.3%	1978
Caribou County (this page)	45	26.7%	66.7%	6.7%	1985
Clark County	40	22.5%	65%	12.5%	1977
Teton County	37	43.2%	51.4%	5.4%	1992

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

Similar inventory size

Nearest county inventories outside ID (45 bridges here).

Dawson County, GA · 45 bridges
Miller County, GA · 45 bridges
Twiggs County, GA · 45 bridges
Hubbard County, MN · 45 bridges

Similar average build year

Nearest mean year-built outside ID (1985 here).

Hillsborough County, FL · avg 1985 · 840 bridges
Lancaster County, NE · avg 1985 · 661 bridges
Nueces County, TX · avg 1985 · 528 bridges
Grayson County, TX · avg 1985 · 513 bridges

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

All 45 Good 12 Fair 30 Poor 3

All bridges (45)

Sort:

Caribou County Bridge Snapshot

Condition distribution

Caribou County's Poor-condition bridges carry 205 vehicle crossings a day

28.9% of Caribou County's bridges have passed the 50-year mark

One structure carries 48.8% of the county's Poor-condition bridge traffic

How Caribou 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

All bridges (45)

MINGO ROAD

STUMP GS ROAD

BURTON ROAD

STC 1775;TURNER RD

KELLY TOPONCE ROAD

SLUG CREEK RD

CHUB FLAT RD.

GOVERNMENT DAM RD

SH 34

VALLEY VIEW DRIVE

SH 34

SMOKY CANYON ROAD

STC 1769;RIVER RD

STC 1759;OLD HW 30

STATELINE RD;WY114

SH 34

SH 34

BAILEY ROAD

KELLY TOPONCE ROAD

2ND BRIDGE ROAD

GIBSON LANE

SH 34

NIPPER ROAD

PEBBLE CREEK ROAD

LAST CHANCE LANE

US 30

ANDERSON ROAD

COUNTY ROAD

SH 34

TINCUP JCT ROAD

BLACKFOOT RIVER RD

STC 1759;OLD HW 30

TIN CUP ROAD

STC 1775;TURNER RD

SANT ROAD

KELLY TOPONCE RD

SH 34

SH 34

TRAIL CREEK ROAD

SH 34

SH 34

SH 34

DIAMOND CREED ROAD

8 MILE ROAD

CHESTERFIELD RES R

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