French Line Road over Duff Drain
Sanilac County, Michigan · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- French Line Road over Duff Drain in Sanilac County, Michigan, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the culvert, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 2001, making it 24 years old at the 2025 inventory.
- It carries about 435 vehicles a day (traffic count year 2016).
- Its listed owner is the county highway agency.
- It is one of 95 of the 170 inventoried bridges in Sanilac County rated fair (55.9%); 25 (14.7%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- It was rated good in the 2024 inventory and is now fair (culvert 7 to 6).
- Its most recent inspection on record is dated April 2024, on a 24-month routine inspection cycle.
- A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.
View this bridge on a map → (43.35816, -83.02386)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Culvert | 7 | 6 | Satisfactory condition |
Bridge details
| Structure | Aluminum or iron culvert |
| Length | about 22 ft |
| Location | Sec 23-26 Marlette Twp |
| NBI structure number | 000000000009559 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | April 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Michigan department of transportation.
Busiest bridges in Sanilac County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| M-90 over Mills Creek | 2023 | 8,400 | Good |
| M-90 over Black River | 2023 | 8,400 | Good |
| M-25 over Mill Creek | 2016 | 7,775 | Good |
| M-46 over Black River | 1947 | 5,462 | Poor |
| M-90 over Spring Creek | 2000 | 5,001 | Good |
| M-90 over W Br Mills Creek | 2006 | 5,001 | Good |
All bridges nearby: Sanilac County, MI bridge conditions · every bridge in Sanilac County · Michigan bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.