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Hwy 312 over RR

Yellowstone County, Montana · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

Hwy 312 over RR in Yellowstone County, Montana, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the deck, rated 6 (satisfactory condition) on the 0-9 scale.
It was built in 2004, making it 21 years old at the 2025 inventory.
It carries about 401 vehicles a day (traffic count year 2023).
Its listed owner is the state highway agency.
It is one of 186 of the 290 inventoried bridges in Yellowstone County rated fair (64.1%); 7 (2.4%) are rated poor.
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.

Component ratings


Structure	Continuous prestressed concrete stringer or multi-beam girder
Length	about 318 ft
Location	1M W Pompey`s Pillar
NBI structure number	S00568000+00621
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the Montana department of transportation.

Bridge	Built	Vehicles/day	Condition
I90 over MT Power RR Spur	2023	29,488	Good
I 90 over City County Drain Ditch	1966	27,985	Fair
King Ave W over Bbwa Canal	1994	26,602	Fair
Mullowney Ln over RR	2007	23,980	Good
Mullowney Ln over RR	2007	23,980	Fair
US 87 over Int Lockwood I 90	1966	23,199	Fair