Old HWY 312 over Yellowstone River 170
PoorYellowstone County, Montana · Huntley · Structure no. L56788012+07001
- Built
- 1949
- 76 years old
- Condition
- Poor
- inspected July 2023
- Type
- Girder and Floorbeam System
- Steel Continuous
- Length
- 1,022 ft
- 6 main spans
- Daily traffic
- 4,005
- 2023 count
- Owner
- State
- State Highway Agency
About this bridge
Old HWY 312 over Yellowstone River 170 is a steel continuous girder and floorbeam system carrying Old HWY 312 over Yellowstone River 170 in Yellowstone County, Montana. It was built in 1949, so it is 76 years old, older than the Montana average of 47 years.
The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.
It carries about 4,005 vehicles a day, roughly 2% of them trucks, projected to reach 4,205 by 2043. The structure is 1,022 ft (311.5 m) long and 34 ft wide. If it were closed, the detour would be 13 mi (21 km).
Location
Open in Google MapsCondition and inspection
The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 4 Poor | Advanced section loss, deterioration, spalling or scour. |
| Superstructure | 6 Satisfactory | Structural elements show some minor deterioration. |
| Substructure | 5 Fair | All primary structural elements are sound but may have minor section loss, cracking, spalling or scour. |
| Channel and channel protection | 6 Satisfactory | Structural elements show some minor deterioration. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was Old HWY 312 over Yellowstone River 170 built?
It was built in 1949, making it 76 years old in 2025.
What condition is Old HWY 312 over Yellowstone River 170 in?
The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in July 2023.
How much traffic does Old HWY 312 over Yellowstone River 170 carry?
About 4,005 vehicles per day (2023 count), of which roughly 2% are trucks.
How long is Old HWY 312 over Yellowstone River 170?
The structure is 1,022 ft (311.5 m) long with a longest span of 185 ft (56.4 m) and a deck 34 ft wide.
Who owns Old HWY 312 over Yellowstone River 170?
It is owned by the State Highway Agency.