County profile · official public datasets

Miami County, OH

315 public highway bridges tracked in the FHWA National Bridge Inventory: 72.1% rated Good, 21% Fair, 7% Poor.

315
Public bridges: 72.1%
Good condition: 7%
Poor condition

The verdict

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

Miami 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.

65th
of 88 on Poor share: 7%
Poor-condition share: 315
public highway bridges: 1983
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.

Miami County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Miami County ranks #65 of 88 Ohio counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7%). Miami County, Ohio contains 315 public highway bridges. Roughly 72.1% are rated “Good,” 21% “Fair,” and 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

315

Public highway bridges in Miami County

Good condition

72.1%

227 of 315 rated 7-9

Fair condition

21%

66 of 315 rated 5-6

Poor condition

22 of 315 rated 4 or below

In-state Poor-share rank

#65 of 88

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

Condition distribution

Share of 315 NBI-tracked bridges by lowest applicable component rating.

Good

72.1% (227)

Fair

21% (66)

Poor

7% (22)

Miami County's Poor-condition bridges carry 22,399 vehicle crossings a day

That is 1.2% of the county's reported daily bridge traffic on 7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,018 crossings a day against 6,968 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 315 of 315 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

41.9% of Miami County's bridges have passed the 50-year mark

132 of the 315 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 72.1% 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 14.4% of the county's Poor-condition bridge traffic

KESSLER-FREDERICK over STONER DITCH, built 1954, carries 3,227 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 22-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 22,399 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

1
1920s

3
1930s

1
1940s

3
1950s

48
1960s

60
1970s

31
1980s

29
1990s

36
2000s

42
2010s

41
2020s

19

What this shows Construction peaked in the 1960s, when 60 of the county's bridges still in the inventory were built, which is 19% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1983, 6 years newer than the Ohio average of 1977.

How Miami County compares with Ohio's closest counties by inventory size

The 5 Ohio counties nearest Miami County in number of bridges, with their condition splits. Its 7% Poor share is the 4th-lowest of these 6. Its average build year of 1983 against a peer-group mean of 1978 is 5 years newer.

Showing the 5 closest of 87 Ohio counties eligible for comparison.

Bridge inventory size and condition shares for Miami County and the 5 Ohio counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Fairfield County	320	56.6%	38.4%	5%	1973
Clermont County	319	61.4%	30.1%	8.5%	1972
Van Wert County	317	89%	11%	0%	1982
Miami County (this page)	315	72.1%	21%	7%	1983
Huron County	311	58.2%	33.8%	8%	1982
Belmont County	310	52.3%	42.6%	5.2%	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 Miami 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 Miami County, both outside Ohio so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside OH (315 bridges here).

Wyandotte County, KS · 315 bridges
Saginaw County, MI · 315 bridges
Monroe County, PA · 315 bridges
Buchanan County, IA · 316 bridges

Similar average build year

Nearest mean year-built outside OH (1983 here).

Dallas County, TX · avg 1983 · 3,230 bridges
Bexar County, TX · avg 1983 · 2,342 bridges
Sedgwick County, KS · avg 1983 · 1,333 bridges
Will County, IL · avg 1983 · 649 bridges

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

All 315 Good 227 Fair 66 Poor 22

Good-condition bridges (227)

Sort:

Miami County Bridge Snapshot

Condition distribution

Miami County's Poor-condition bridges carry 22,399 vehicle crossings a day

41.9% of Miami County's bridges have passed the 50-year mark

One structure carries 14.4% of the county's Poor-condition bridge traffic

How Miami County compares with Ohio's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Good-condition bridges (227)

CR46 MILTON-POTTSD

C166 Tipp-Elizbeth

CR6 MIAMI-SHELBY E

CR7A DAYTON-BRANDT

C0014 Troy-Sidney

CR16 PETERSON RD.

CR37 FENNER RD.

TR101 Perry Rd.

CR158 Children"s H

TR 167 Rudy Rd.

CR 177 PALMER RD.

CR179 ROSS RD.

TR210 - Sodom Rd.

CR 35 Washington

CR50 Shiloh Rd.

IR-75

CR137 Swailes Rd.

CR193 TROY-URBANA

T-211 RUGGED HILL

CR12 TROY-FREDERIC

LANDMAN MILL

TR76 Owens Rd.

TR25 SODOM-BALLOU

ADAMS ST. - TROY-S

EXPERIMENT FARM

CR17 Loy Rd.

CR28 VERSAILLES R

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