Total bridges
167
Public highway bridges in Gratiot County
County profile · official public datasets
167 public highway bridges tracked in the FHWA National Bridge Inventory: 40.7% rated Good, 47.3% Fair, 12% Poor.
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Gratiot County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.
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.
According to the Federal Highway Administration's 2024 National Bridge Inventory, Gratiot County ranks #45 of 83 Michigan counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 12%). Gratiot County, Michigan contains 167 public highway bridges. Roughly 40.7% are rated “Good,” 47.3% “Fair,” and 12% “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
167
Public highway bridges in Gratiot County
Good condition
40.7%
68 of 167 rated 7-9
Fair condition
47.3%
79 of 167 rated 5-6
Poor condition
12%
20 of 167 rated 4 or below
In-state Poor-share rank
#45 of 83
Among Michigan counties with 5+ bridges, lower share ranks better
Share of 167 NBI-tracked bridges by lowest applicable component rating.
That is 18.1% of the county's reported daily bridge traffic on 12% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 3,384 crossings a day against 1,128 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 167 of 167 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
69 of the 167 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 40.7% 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.
M-46 & US-127BR over US-127, built 1961, carries 11,219 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 20-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 67,679 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
167 bridges with a recorded construction year, grouped by decade
1900–1909
3 bridges
1910–1919
1 bridges
1920–1929
4 bridges
1930–1939
10 bridges
1940–1949
4 bridges
1950–1959
15 bridges
1960–1969
29 bridges
1970–1979
21 bridges
1980–1989
34 bridges
1990–1999
19 bridges
2000–2009
14 bridges
2010–2019
12 bridges
2020–2029
1 bridges
What this shows Construction peaked in the 1980s, when 34 of the county's bridges still in the inventory were built, which is 20.4% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1975) matches the Michigan average (1976).
The 5 Michigan counties nearest Gratiot County in number of bridges, with their condition splits. Its 12% Poor share is the 4th-lowest of these 6. Its average build year of 1975 against a peer-group mean of 1978 is in line with the group.
Showing the 5 closest of 82 Michigan counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Sanilac County | 171 | 31.6% | 58.5% | 9.9% | 1978 |
| Gratiot County (this page) | 167 | 40.7% | 47.3% | 12% | 1975 |
| Bay County | 166 | 30.1% | 53% | 16.9% | 1974 |
| Livingston County | 165 | 26.7% | 58.8% | 14.5% | 1974 |
| Lapeer County | 163 | 36.2% | 54.6% | 9.2% | 1982 |
| Shiawassee County | 163 | 45.4% | 45.4% | 9.2% | 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 Gratiot County's. Source: FHWA National Bridge Inventory, 2024 release.
Two NBI-derived peer sets for Gratiot County, both outside Michigan so the neighborhoods are not the same-state size table above.
Nearest county inventories outside MI (167 bridges here).
Nearest mean year-built outside MI (1975 here).
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Over: PINE CREEK
SEC 33 NEWARK TWP, Gratiot, MI
Over: PINE RIVER
SEC 27-34 SUMNER TWP, Gratiot, MI
Over: NORTH SHADE DRAIN
SEC 2-3 NORTH SHADE TWP, Gratiot, MI
Over: DRAIN #290
SEC 1 SUMNER TWP, Gratiot, MI
Over: US-127
2.0 MI S OF ISABELLA COL, Gratiot, MI
Over: PINE RIVER
SEC 18 BETHANY TWP, Gratiot, MI
Over: PINE RIVER
0.2 MI S US-27BR IN ALMA, Gratiot, MI
Over: NORTH END DRAIN
SEC 21-22 ARCADA TWP, Gratiot, MI
Over: DRAIN #96
SEC 36 SEVILLE TWP, Gratiot, MI
Over: BEAVER CREEK
SEC 7 LAFAYETTE TWP, Gratiot, MI
Over: NORTH SHADE DRAIN
SEC 31 NEWARK TWP, Gratiot, MI
Over: DRAIN #73
SEC 32 PINE RIVER TWP, Gratiot, MI
Over: PINE RIVER
IN ST LOUIS, Gratiot, MI
Over: CARPENTER CREEK
SEC 31 SUMNER TWP, Gratiot, MI
Over: BUSH CREEK DRAIN
SEC 2 BETHANY TWP, Gratiot, MI
Over: NORTH SHADE DRAIN
SEC 29-32 NEWARK TWP, Gratiot, MI
Over: GRILL & CONE DRAIN
SEC 31-32 NORTH SHADE TWP, Gratiot, MI
Over: NORTH SHADE DRAIN
SEC 1 NORTH SHADE TWP, Gratiot, MI
Over: DRAIN #115
SEC 12-13 NORTH STAR TWP, Gratiot, MI
Over: DRAIN #115
SEC 11-12 NORTH STAR TWP, Gratiot, MI
Over: BEAR CREEK
SEC 1-2 WASHINGTON TWP, Gratiot, MI
Over: OTTER CREEK
FULTON TWP SEC 20, Gratiot, MI
Over: PINE RIVER
0.5 MI W OF ST LOUIS, Gratiot, MI
Over: PINE RIVER
0.5 MI W OF ST LOUIS, Gratiot, MI
Over: US-127 / MID MI PATH
@ N ITHACA CITY LTS, Gratiot, MI
Over: US-127 NB / MID MI PATH
2.5 MI N OF ITHACA, Gratiot, MI
Over: BAD RIVER
SEC 8-9 HAMILTON TWP, Gratiot, MI
Over: WOLF & BEAR CREEK DRAIN
SEC 18 ELBA TWP, Gratiot, MI
Over: US-127 SB
2.5 MI N OF ITHACA, Gratiot, MI
Over: PINE RIVER
IN CITY OF ALMA, Gratiot, MI
Over: PINE RIVER
SEC 4-5 BETHANY TWP, Gratiot, MI
Over: BAD RIVER DRAIN
SEC 7-18 HAMILTON TWP, Gratiot, MI
Over: WOLF & BEAR CREEK DRAIN
SEC 18-19 ELBA TWP, Gratiot, MI
Over: MICHIGAN AVE
NE LTS OF ALMA, Gratiot, MI
Over: MICHIGAN AVE
NE LTS OF ALMA, Gratiot, MI
Over: PINE RIVER
SEC 33 SUMNER TWP, Gratiot, MI
Over: PINE RIVER
CITY OF ST LOUIS, Gratiot, MI
Over: MAPLE RIVER
SEC 21-28 ELBA TWP, Gratiot, MI
Over: NORTH SHADE DRAIN
SEC 1-2 NORTH SHADE TWP, Gratiot, MI
Over: MDOT RR CORRIDOR
0.5 MI E OF ITHACA, Gratiot, MI
Over: BEAVER CREEK DRAIN
SEC 36 WHEELER TWP, Gratiot, MI
Over: US-127 BR (POLK RD)
2.0 MI N OF ITHACA, Gratiot, MI
Over: BEAVER CREEK
SEC 3-4 LAFAYETTE TWP, Gratiot, MI
Over: MDOT RR CORRIDOR
0.5 MI E OF ITHACA, Gratiot, MI
Over: MAPLE RIVER
SEC 19-20 ELBA TWP, Gratiot, MI
Over: MAPLE RIVER
SEC 28-33 ELBA TWP, Gratiot, MI
Over: N BR BAD RIVER
5.3 MI SE OF ITHACA, Gratiot, MI
Over: DRAIN #1
SEC 29-32 NEWARK TWP, Gratiot, MI
Over: US-127 SB
5.0 MI N OF ITHACA, Gratiot, MI
Over: DRAIN #1
SEC 10-15 NEWARK TWP, Gratiot, MI
Read our methodology - how this data is sourced, computed, and verified.
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.