County profile · official public datasets

Monroe County, MI

297 public highway bridges tracked in the FHWA National Bridge Inventory: 30% rated Good, 54.5% Fair, 15.5% Poor.

297
Public bridges: 30%
Good condition: 15.5%
Poor condition

The verdict

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

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

59th
of 83 on Poor share: 15.5%
Poor-condition share: 297
public highway bridges: 1974
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.

Monroe County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Monroe County ranks #59 of 83 Michigan counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 15.5%). Monroe County, Michigan contains 297 public highway bridges. Roughly 30% are rated “Good,” 54.5% “Fair,” and 15.5% “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

297

Public highway bridges in Monroe County

Good condition

30%

89 of 297 rated 7-9

Fair condition

54.5%

162 of 297 rated 5-6

Poor condition

15.5%

46 of 297 rated 4 or below

In-state Poor-share rank

#59 of 83

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

Condition distribution

Share of 297 NBI-tracked bridges by lowest applicable component rating.

Good

30% (89)

Fair

54.5% (162)

Poor

15.5% (46)

Monroe County's Poor-condition bridges carry 203,824 vehicle crossings a day

That is 7.9% of the county's reported daily bridge traffic on 15.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 4,431 crossings a day against 9,265 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 297 of 297 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

53.5% of Monroe County's bridges have passed the 50-year mark

159 of the 297 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 30% 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 33.3% of the county's Poor-condition bridge traffic

I-75 over CONRAIL RAISIN R FRONT, built 1955, carries 67,800 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 46-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 203,824 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

1
1910s

1
1920s

16
1930s

13
1940s

6
1950s

55
1960s

37
1970s

49
1980s

30
1990s

21
2000s

35
2010s

19
2020s

13

What this shows Construction peaked in the 1950s, when 55 of the county's bridges still in the inventory were built, which is 18.5% of those with a recorded year. That cohort is now 65 to 74 years old in the 2024 inventory. Its average build year (1974) matches the Michigan average (1976).

How Monroe County compares with Michigan's closest counties by inventory size

The 5 Michigan counties nearest Monroe County in number of bridges, with their condition splits. Its 15.5% Poor share is the 4th-lowest of these 6. Its average build year of 1974 against a peer-group mean of 1979 is 5 years older.

Showing the 5 closest of 82 Michigan counties eligible for comparison.

Bridge inventory size and condition shares for Monroe County and the 5 Michigan counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
St. Clair County	327	41.3%	50.5%	8.3%	1985
Saginaw County	315	28.9%	52.7%	18.4%	1979
Monroe County (this page)	297	30%	54.5%	15.5%	1974
Berrien County	272	27.6%	66.5%	5.9%	1979
Washtenaw County	262	23.3%	56.5%	20.2%	1975
Ottawa County	254	40.9%	52.8%	6.3%	1977

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

Similar inventory size

Nearest county inventories outside MI (297 bridges here).

Crawford County, KS · 297 bridges
Kingfisher County, OK · 297 bridges
Sarasota County, FL · 298 bridges
Rutherford County, NC · 298 bridges

Similar average build year

Nearest mean year-built outside MI (1974 here).

Knox County, TN · avg 1974 · 588 bridges
Summit County, OH · avg 1974 · 563 bridges
Onondaga County, NY · avg 1974 · 472 bridges
Orange County, NY · avg 1974 · 472 bridges

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

All 297 Good 89 Fair 162 Poor 46

Fair-condition bridges (162)

Sort:

Monroe County Bridge Snapshot

Condition distribution

Monroe County's Poor-condition bridges carry 203,824 vehicle crossings a day

53.5% of Monroe County's bridges have passed the 50-year mark

One structure carries 33.3% of the county's Poor-condition bridge traffic

How Monroe County compares with Michigan's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Fair-condition bridges (162)

US-23 NB

US-23 SB

I-75 SB

I-75

I-275 NB

SIGLER RD

I-75 SB

MENTEL RD

MILAN-OAKVILLE RD

PETERSBURG ROAD

HERR ROAD

I-75 SB

I-75 RAMP B

US-24

SUDER ROAD

DENNISON RD

OSTRANDER RD

MORTAR CREEK RD

GAYNIER RD

I-75 NB

US-23 SB

I-75

I-75NB TO I-275NB

NORTH DIXIE HWY

HISER ROAD

OLD US-223

I-275 SB

SUMMIT ST

STONE ROAD

I-275 NB

US-23 SB

US-24

I-275 SB

I-275 NB

I-75

KENTUCKY AVENUE

OTTER CREEK RD

I-275 NB

LEWIS AVE

I-275 SB

I-275 SB

US-23

READY RD

PETERSBURG RD

NORTH DIXIE HWY

US-24

MILAN OAKVILLE RD

PETERSBURG RD

I-75 (NB EX RAMP)

LAPLAISANCE RD

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