County profile · official public datasets

Tama County, IA

337 public highway bridges tracked in the FHWA National Bridge Inventory: 34.4% rated Good, 31.2% Fair, 34.4% Poor.

337
Public bridges: 34.4%
Good condition: 34.4%
Poor condition

The verdict

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

Tama County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

91st
of 99 on Poor share: 34.4%
Poor-condition share: 337
public highway bridges: 1976
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.

Tama County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Tama County ranks #91 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 34.4%). Tama County, Iowa contains 337 public highway bridges. Roughly 34.4% are rated “Good,” 31.2% “Fair,” and 34.4% “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

337

Public highway bridges in Tama County

Good condition

34.4%

116 of 337 rated 7-9

Fair condition

31.2%

105 of 337 rated 5-6

Poor condition

34.4%

116 of 337 rated 4 or below

In-state Poor-share rank

#91 of 99

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

Condition distribution

Share of 337 NBI-tracked bridges by lowest applicable component rating.

Good

34.4% (116)

Fair

31.2% (105)

Poor

34.4% (116)

Tama County's Poor-condition bridges carry 22,557 vehicle crossings a day

That is 12.7% of the county's reported daily bridge traffic on 34.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 194 crossings a day against 1,091 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 335 of 337 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

42.1% of Tama County's bridges have passed the 50-year mark

142 of the 337 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 34.4% 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 12.8% of the county's Poor-condition bridge traffic

BUS US 30 over DEER CREEK, built 1953, carries 2,887 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 116-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 22,557 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

2
1900s

7
1910s

10
1920s

12
1930s

10
1940s

29
1950s

28
1960s

33
1970s

24
1980s

49
1990s

42
2000s

44
2010s

36
2020s

11

What this shows Construction peaked in the 1980s, when 49 of the county's bridges still in the inventory were built, which is 14.5% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1976) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Tama County in number of bridges, with their condition splits. Its 34.4% Poor share is the 6th-lowest of these 6. Its average build year of 1976 against a peer-group mean of 1980 is in line with the group.

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

Bridge inventory size and condition shares for Tama County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Fayette County	362	35.1%	40.3%	24.6%	1974
Dubuque County	346	50.6%	40.8%	8.7%	1989
Winneshiek County	342	37.1%	45.3%	17.5%	1967
Tama County (this page)	337	34.4%	31.2%	34.4%	1976
Buchanan County	316	42.4%	50.9%	6.6%	1985
Adair County	306	46.7%	39.9%	13.4%	1983

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

Similar inventory size

Nearest county inventories outside IA (337 bridges here).

Placer County, CA · 337 bridges
Cowley County, KS · 337 bridges
Ouachita County, LA · 337 bridges
Windham County, VT · 337 bridges

Similar average build year

Nearest mean year-built outside IA (1976 here).

Marion County, IN · avg 1976 · 958 bridges
Mohave County, AZ · avg 1976 · 641 bridges
Comanche County, OK · avg 1976 · 593 bridges
Prince George's County, MD · avg 1976 · 576 bridges

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

All 337 Good 116 Fair 105 Poor 116

All bridges (337)

Sort:

Tama County Bridge Snapshot

Condition distribution

Tama County's Poor-condition bridges carry 22,557 vehicle crossings a day

42.1% of Tama County's bridges have passed the 50-year mark

One structure carries 12.8% of the county's Poor-condition bridge traffic

How Tama 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

All bridges (337)

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