US-31 SB over CSX RR
Mason County, Michigan · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- US-31 SB over CSX RR in Mason County, Michigan, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the superstructure, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1988, making it 37 years old at the 2025 inventory.
- It carries about 2,498 vehicles a day (traffic count year 2007).
- Its listed owner is the state highway agency.
- It is one of 41 of the 66 inventoried bridges in Mason County rated fair (62.1%); 4 (6.1%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its class is unchanged from 2024 (fair), but component ratings moved: superstructure 6 to 5.
- 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 → (43.95136, -86.3851)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 6 | 5 | Fair condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 140 ft |
| Location | 3.1 Mi E of Ludington |
| NBI structure number | 000000000006648 |
| 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) | N: not over a waterway |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Michigan department of transportation.
Busiest bridges in Mason County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Old US-31 over CSX RR | 1935 | 11,200 | Good |
| Old US-31 over Durham Creek | 1925 | 8,600 | Fair |
| Old US-31 over Pere Marquette River | 1925 | 7,076 | Fair |
| Old US-31 over Pere Marquette River | 1924 | 6,828 | Fair |
| US-31 over S Br Lincoln River | 1992 | 6,578 | Fair |
| US-31 over N Br Lincoln River | 1992 | 6,578 | Fair |
All bridges nearby: Mason County, MI bridge conditions · every bridge in Mason County · Michigan bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.