County profile · official public datasets

Ingham County, MI

241 public highway bridges tracked in the FHWA National Bridge Inventory: 15.8% rated Good, 68.9% Fair, 15.4% Poor.

241
Public bridges: 15.8%
Good condition: 15.4%
Poor condition

The verdict

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

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

56th
of 83 on Poor share: 15.4%
Poor-condition share: 241
public highway bridges: 1972
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.

Ingham County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Ingham County ranks #56 of 83 Michigan counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 15.4%). Ingham County, Michigan contains 241 public highway bridges. Roughly 15.8% are rated “Good,” 68.9% “Fair,” and 15.4% “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

241

Public highway bridges in Ingham County

Good condition

15.8%

38 of 241 rated 7-9

Fair condition

68.9%

166 of 241 rated 5-6

Poor condition

15.4%

37 of 241 rated 4 or below

In-state Poor-share rank

#56 of 83

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

Condition distribution

Share of 241 NBI-tracked bridges by lowest applicable component rating.

Good

15.8% (38)

Fair

68.9% (166)

Poor

15.4% (37)

Ingham County's Poor-condition bridges carry 499,378 vehicle crossings a day

That is 13.5% of the county's reported daily bridge traffic on 15.4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 13,497 crossings a day against 4,689 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 241 of 241 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

70.1% of Ingham County's bridges have passed the 50-year mark

169 of the 241 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 15.8% 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 7% of the county's Poor-condition bridge traffic

I-496 EB over RED CEDAR RIVER & RAMP V, built 1970, carries 34,831 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 37-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 499,378 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

2
1920s

9
1930s

5
1940s

12
1950s

12
1960s

99
1970s

41
1980s

9
1990s

8
2000s

26
2010s

13
2020s

5

What this shows Construction peaked in the 1960s, when 99 of the county's bridges still in the inventory were built, which is 41.1% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1972) matches the Michigan average (1976).

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

The 5 Michigan counties nearest Ingham County in number of bridges, with their condition splits. Its 15.4% Poor share is the 4th-lowest of these 6. Its average build year of 1972 against a peer-group mean of 1978 is 6 years older.

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

Bridge inventory size and condition shares for Ingham County and the 5 Michigan counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Washtenaw County	262	23.3%	56.5%	20.2%	1975
Ottawa County	254	40.9%	52.8%	6.3%	1977
Allegan County	244	24.2%	59%	16.8%	1978
Tuscola County	242	33.9%	61.2%	5%	1980
Ingham County (this page)	241	15.8%	68.9%	15.4%	1972
Lenawee County	225	47.6%	39.6%	12.9%	1981

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

Similar inventory size

Nearest county inventories outside MI (241 bridges here).

Sumter County, AL · 241 bridges
Hardin County, IA · 241 bridges
Iowa County, IA · 241 bridges
Barber County, KS · 241 bridges

Similar average build year

Nearest mean year-built outside MI (1972 here).

Santa Clara County, CA · avg 1972 · 964 bridges
Madison County, AL · avg 1972 · 710 bridges
Kern County, CA · avg 1972 · 668 bridges
York County, PA · avg 1972 · 569 bridges

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

All 241 Good 38 Fair 166 Poor 37

Fair-condition bridges (166)

Sort:

Ingham County Bridge Snapshot

Condition distribution

Ingham County's Poor-condition bridges carry 499,378 vehicle crossings a day

70.1% of Ingham County's bridges have passed the 50-year mark

One structure carries 7% of the county's Poor-condition bridge traffic

How Ingham 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 (166)

JOLLY ROAD

US-127 SB

PINE ST

I-496 WB

HAGADORN ROAD

BASE LINE ROAD

BELLEVUE RD

I-496 WB

I-496 EB RAMP

M-52

I-96 EB

I-96 WB

US-127 NB

I-96 WB

US-127 NB

KALAMAZOO STREET

PENNSYLVANIA AVE

HARPER RD

I-496 EB

N MARTINLUTHERKING

KALAMAZOO @ CIR DR

M-143 E MICH AVE

I-496 EB & SERV DR

M-43 EB

SB I-496 TO EB 96

I-496 WB RAMP

I-496 EB

M-99 NB

CLEMENS ST

I-496 WB

ONONDAGA ROAD

HUNGERFORD ST

HOWELL RD

I-496 EB

ST JOSEPH-MAIN ST

M-43

RAMP H

KALAMAZOO STREET

OKEMOS RD

US-127 SB

M-43 EB (SAGINAW)

NAKOMA DRIVE

KIPP RD

I-96 EB

I-96 WB

I-96 EB

I-96 WB

HARPER ROAD

COLLEGE ROAD

US-127 SB

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