County profile · official public datasets

Audubon County, IA

206 public highway bridges tracked in the FHWA National Bridge Inventory: 33.5% rated Good, 48.1% Fair, 18.4% Poor.

206
Public bridges: 33.5%
Good condition: 18.4%
Poor condition

The verdict

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

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

Top 46%
lowest Poor share in state: 18.4%
Poor-condition share: 206
public highway bridges: 1968
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.

Audubon County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Audubon County ranks #46 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 18.4%). Audubon County, Iowa contains 206 public highway bridges. Roughly 33.5% are rated “Good,” 48.1% “Fair,” and 18.4% “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

206

Public highway bridges in Audubon County

Good condition

33.5%

69 of 206 rated 7-9

Fair condition

48.1%

99 of 206 rated 5-6

Poor condition

18.4%

38 of 206 rated 4 or below

In-state Poor-share rank

#46 of 99

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

Condition distribution

Share of 206 NBI-tracked bridges by lowest applicable component rating.

Good

33.5% (69)

Fair

48.1% (99)

Poor

18.4% (38)

Audubon County's Poor-condition bridges carry 1,856 vehicle crossings a day

That is 4% of the county's reported daily bridge traffic on 18.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 49 crossings a day against 250 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 204 of 206 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

58.7% of Audubon County's bridges have passed the 50-year mark

121 of the 206 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 33.5% 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 33.2% of the county's Poor-condition bridge traffic

EDGERTON ST over DRAINAGE, built 1960, carries 616 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 38-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 1,856 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

2
1910s

1
1920s

17
1930s

31
1940s

17
1950s

21
1960s

17
1970s

25
1980s

16
1990s

19
2000s

19
2010s

15
2020s

6

What this shows Construction peaked in the 1930s, when 31 of the county's bridges still in the inventory were built, which is 15% of those with a recorded year. That cohort is now 85 to 94 years old in the 2024 inventory. Its average build year is 1968, 11 years older than the Iowa average of 1979.

How Audubon County compares with Iowa's closest counties by inventory size

The 5 Iowa counties nearest Audubon County in number of bridges, with their condition splits. Its 18.4% Poor share is the 3rd-lowest of these 6. Its average build year of 1968 against a peer-group mean of 1978 is 10 years older.

Showing the 5 closest of 98 Iowa counties eligible for comparison.

Bridge inventory size and condition shares for Audubon County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Howard County	210	41.9%	35.2%	22.9%	1984
Montgomery County	210	21%	53.8%	25.2%	1973
Shelby County	207	36.2%	54.1%	9.7%	1979
Washington County	207	39.6%	44.4%	15.9%	1980
Audubon County (this page)	206	33.5%	48.1%	18.4%	1968
Pocahontas County	201	19.4%	55.2%	25.4%	1974

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

Similar inventory size

Nearest county inventories outside IA (206 bridges here).

Dale County, AL · 206 bridges
Henry County, IN · 206 bridges
Bourbon County, KS · 206 bridges
Pemiscot County, MO · 206 bridges

Similar average build year

Nearest mean year-built outside IA (1968 here).

Montgomery County, PA · avg 1968 · 828 bridges
San Joaquin County, CA · avg 1968 · 644 bridges
Providence County, RI · avg 1968 · 476 bridges
Imperial County, CA · avg 1968 · 444 bridges

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

All 206 Good 69 Fair 99 Poor 38

Poor-condition bridges (38)

Sort:

Audubon County Bridge Snapshot

Condition distribution

Audubon County's Poor-condition bridges carry 1,856 vehicle crossings a day

58.7% of Audubon County's bridges have passed the 50-year mark

One structure carries 33.2% of the county's Poor-condition bridge traffic

How Audubon County compares with Iowa's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Poor-condition bridges (38)

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