I 15 over Marias River
Toole County, Montana · rated Good in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- I 15 over Marias River in Toole County, Montana, is rated in good condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 7 (good condition) on the 0-9 scale.
- It was built in 1976, making it 49 years old at the 2025 inventory.
- It carries about 1,311 vehicles a day (traffic count year 2023).
- Its listed owner is the state highway agency.
- It is one of 14 of the 35 inventoried bridges in Toole County rated good (40.0%); 0 (0.0%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- It was rated fair in the 2024 inventory and is now good (deck 6 to 8).
- Its most recent inspection on record is dated August 2023, on a 24-month routine inspection cycle.
- A good rating means every major component - deck, superstructure, substructure, or culvert - is rated 7 or higher on FHWA's 0-9 scale: no more than minor problems.
View this bridge on a map → (48.42733, -111.89158)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 8 | Very good condition |
| Superstructure | 8 | 8 | Very good condition |
| Substructure | 7 | 7 | Good condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 483 ft |
| Location | 6M S Shelby |
| NBI structure number | I00015357+00752 |
| Condition class | Good |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | August 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 5: foundations stable, scour within the limits of the footing or piles |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Montana department of transportation.
Busiest bridges in Toole County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| S 67 over Front St-rr | 1938 | 2,161 | Fair |
| I 15 over Sep County Road | 1976 | 1,520 | Fair |
| I 15 over Sep County Road | 1976 | 1,520 | Fair |
| I 15 over Marias River | 1976 | 1,311 | Good |
| I 15 over Int Shelby-rr | 1960 | 1,021 | Fair |
| I 15 over Int Shelby-rr | 1960 | 1,021 | Fair |
All bridges nearby: Toole County, MT bridge conditions · every bridge in Toole County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.