M-28 over Rock River
Alger County, Michigan · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- M-28 over Rock River in Alger County, Michigan, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 1932 and reconstructed in 1975, making it 93 years old at the 2025 inventory.
- It carries about 3,093 vehicles a day (traffic count year 2007).
- Its listed owner is the state highway agency.
- It is one of 30 of the 53 inventoried bridges in Alger County rated fair (56.6%); 7 (13.2%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated May 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 → (46.46382, -86.91603)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Steel stringer or multi-beam girder |
| Length | about 40 ft |
| Location | 5.1 Mi NW of Au Train |
| NBI structure number | 000000000000046 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | May 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 Alger County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| M-28 over Anna River | 1949 | 7,171 | Fair |
| East Munising Ave over Anna River | 1978 | 5,715 | Fair |
| M-28 over Au Train River | 1932 | 5,200 | Fair |
| US-41 over Huber Creek | 1987 | 3,609 | Fair |
| M-28 over Sand River | 1939 | 3,093 | Fair |
| M-28 over Laughing Whitefish River | 1939 | 3,093 | Good |
All bridges nearby: Alger County, MI bridge conditions · every bridge in Alger County · Michigan bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.