County profile · official public datasets

Carbon County, MT

80 public highway bridges tracked in the FHWA National Bridge Inventory: 36.3% rated Good, 58.8% Fair, 5% Poor.

80
Public bridges
36.3%
Good condition
5%
Poor condition

The verdict

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

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

Top 36%
lowest Poor share in state
5%
Poor-condition share
80
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.

Carbon County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Carbon County ranks #20 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 5%). Carbon County, Montana contains 80 public highway bridges. Roughly 36.3% are rated “Good,” 58.8% “Fair,” and 5% “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

80

Public highway bridges in Carbon County

Good condition

36.3%

29 of 80 rated 7-9

Fair condition

58.8%

47 of 80 rated 5-6

Poor condition

5%

4 of 80 rated 4 or below

In-state Poor-share rank

#20 of 56

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

Condition distribution

Share of 80 NBI-tracked bridges by lowest applicable component rating.

Good
36.3% (29)
Fair
58.8% (47)
Poor
5% (4)

Carbon County's Poor-condition bridges carry 678 vehicle crossings a day

That is 1.5% of the county's reported daily bridge traffic on 5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 170 crossings a day against 597 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 80 of 80 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

35% of Carbon County's bridges have passed the 50-year mark

28 of the 80 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 36.3% 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 70.5% of the county's Poor-condition bridge traffic

S 78 FH 83 over RED LODGE CREEK, built 1953, carries 478 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 4-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 678 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Carbon County's bridges were built

80 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 2010s, when 17 of the county's bridges still in the inventory were built, which is 21.3% of those with a recorded year. That cohort is now 5 to 14 years old in the 2024 inventory. Its average build year is 1985, 8 years newer than the Montana average of 1977.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

How Carbon County compares with Montana's closest counties by inventory size

The 5 Montana counties nearest Carbon County in number of bridges, with their condition splits. Its 5% Poor share is the 4th-lowest of these 6. Its average build year of 1985 against a peer-group mean of 1975 is 10 years newer.

Showing the 5 closest of 55 Montana counties eligible for comparison.

Bridge inventory size and condition shares for Carbon County and the 5 Montana counties closest to it in inventory size
County Bridges Poor
Stillwater County 92 1.1%
Teton County 82 2.4%
Carbon County (this page) 80 5%
Granite County 73 11%
Custer County 71 1.4%
Glacier County 71 5.6%

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

Similar inventory size

Nearest county inventories outside MT (80 bridges here).

Similar average build year

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

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

All 80 Good 29 Fair 47 Poor 4

Good-condition bridges (29)

East Side Road

Good

Over: Rock Creek

4M S RED LODGE, Carbon, MT

Built 2023 ADT: 100

East Side Road

Good

Over: Rock Creek

7M S Red Lodge, Carbon, MT

Built 2023 ADT: 100

Meeteetse Trail

Good

Over: Rock Creek

1M SE of Red Lodge, Carbon, MT

Built 2023 ADT: 100

2-LANE ROAD

Good

Over: ROCK CREEK

NO DATA ENTERED, Carbon, MT

Built 1970 Load: 20.7 t ADT: 50

TUTTLE LN

Good

Over: E ROSEBUD CREEK 003

3.7M NE ROSCOE, Carbon, MT

Built 2009 Load: 20.9 t ADT: 100

NO DATA ENTERED

Good

Over: WILLOW CREEK

NO DATA ENTERED, Carbon, MT

Built 2010 Load: 22.4 t ADT: 40

NO DATA ENTERED

Good

Over: EAST ROSEBUD CREEK

NO DATA ENTERED, Carbon, MT

Built 2007 Load: 24.9 t ADT: 40

S 72

Good

Over: SILVER TIP CREEK

3M N BELFRY, Carbon, MT

Built 2011 Load: 26.3 t ADT: 1,722

S 308

Good

Over: ROCK CREEK

RED LODGE, Carbon, MT

Built 2003 Load: 26.3 t ADT: 1,246

NO DATA ENTERED

Good

Over: EAST ROSEBUD CREEK

NO DATA ENTERED, Carbon, MT

Built 2007 Load: 26.9 t ADT: 40

HOMESTEADER RD

Good

Over: FIVE MILE CREEK 058

1M NE EDGAR, Carbon, MT

Built 2018 Load: 28.1 t ADT: 100

MONTAQUA RD

Good

Over: ELBOW CREEK 048

3M SW EDGAR, Carbon, MT

Built 2007 Load: 28.2 t ADT: 100

01017: CROOKED CRE

Good

Over: Gypsum Creek

9 mi N of Cowley WY, Carbon, MT

Built 2010 Load: 29.8 t ADT: 25

LUTHER ROSCOE ROAD

Good

Over: BUTCHER CREEK

3.5M NW LUTHER, Carbon, MT

Built 2014 Load: 30.8 t ADT: 100

E RIVER ST

Good

Over: CLARKS FK YELLOWSTNE 053

N EDGE FROMBERG, Carbon, MT

Built 2008 Load: 31.8 t ADT: 1,098

PRYOR MOUNTAIN ROA

Good

Over: BRIDGER CREEK

3M S BRIDGER, Carbon, MT

Built 2020 Load: 32.7 t ADT: 100

NO DATA ENTERED

Good

Over: WEST FORK ROCK CREEK

NO DATA ENTERED, Carbon, MT

Built 2010 Load: 33.0 t ADT: 40

NO DATA ENTERED

Good

Over: WEST FORK ROCK CREEK

NO DATA ENTERED, Carbon, MT

Built 2010 Load: 33.4 t ADT: 40

COTTONWOOD RD

Good

Over: CLARKS FK YELLOWSTNE 028

1M E SILESIA, Carbon, MT

Built 1997 Load: 33.6 t ADT: 414

US 212 FH 59

Good

Over: ROCK CREEK

8M SW RED LODGE, Carbon, MT

Built 1965 Load: 33.6 t ADT: 372

SECONDARY 78

Good

Over: EAST ROSEBUD CREEK

6 MILES SOUTH OF ABSAROKE, Carbon, MT

Built 2019 Load: 35.4 t ADT: 657

US 212

Good

Over: ROCK CREEK

2M N ROBERTS, Carbon, MT

Built 2001 Load: 35.4 t ADT: 2,476

S 72

Good

Over: BEAR CREEK

BELFRY, Carbon, MT

Built 2013 Load: 35.4 t ADT: 1,722

RED LODGE CR RD

Good

Over: RED LODGE CREEK 011

9M NE ROSCOE, Carbon, MT

Built 2017 Load: 36.3 t ADT: 100

E PRYOR RD

Good

Over: FIVE MILE CREEK 057

3M E EDGAR, Carbon, MT

Built 2016 Load: 36.3 t ADT: 411

SHANE RIDGE RD

Good

Over: RED LODGE CREEK 044

2M SW BOYD, Carbon, MT

Built 2013 Load: 38.2 t ADT: 100

MONTAQUA RD

Good

Over: ROCK CREEK 047

MONTAQUA, Carbon, MT

Built 2014 Load: 39.9 t ADT: 100

US 212 FH 59

Good

Over: WEST FORK ROCK CREEK

1M S RED LODGE, Carbon, MT

Built 1980 Load: 42.6 t ADT: 1,068

US 310

Good

Over: SAND CREEK

4M S FROMBERG, Carbon, MT

Built 1987 Load: 99.9 t ADT: 4,760

Read our methodology - how this data is sourced, computed, and verified.

Related

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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.