S 500 over Flatwillow Creek
Petroleum County, Montana · rated Good in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- S 500 over Flatwillow Creek in Petroleum County, Montana, is rated in good condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 7 (good condition) on the 0-9 scale.
- It was built in 1962 and reconstructed in 2015, making it 63 years old at the 2025 inventory.
- It carries about 14 vehicles a day (traffic count year 2023).
- Its listed owner is the county highway agency.
- It is one of 8 of the 26 inventoried bridges in Petroleum County rated good (30.8%); 4 (15.4%) 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 March 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 → (46.92868, -107.93286)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 7 | 7 | Good condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 335 ft |
| Location | 6M SW Mosby |
| NBI structure number | S00500030+00001 |
| Condition class | Good |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | March 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 Petroleum County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| S 200 over Box Elder Creek | 1953 | 539 | Fair |
| S 244 over Mcdonald Creek | 1941 | 245 | Fair |
| S 244 over Pike Creek | 1939 | 233 | Fair |
| S 244 over Drainage | 1935 | 233 | Fair |
| S 244 over Yellow Water Cr-elk CR | 1948 | 233 | Poor |
| S 244 over Drainage | 1940 | 208 | Fair |
All bridges nearby: Petroleum County, MT bridge conditions · every bridge in Petroleum County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.