US Bridges

IRR - I 90 over Bighorn River

Fair

Big Horn County, Montana · Hardin · Structure no. I00090498+01012

Built
1971
54 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
594 ft
3 main spans
Daily traffic
4,258
2023 count
Owner
State
State Highway Agency

About this bridge

IRR - I 90 over Bighorn River is a steel continuous stringer/multi-beam or girder carrying IRR - I 90 over Bighorn River in Big Horn County, Montana. It was built in 1971, so it is 54 years old, older than the Montana average of 47 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 4,258 vehicles a day, roughly 18% of them trucks, projected to reach 4,471 by 2043. The structure is 594 ft (180.9 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesIRR - I 90
CrossesBighorn River
LocationHardin
RouteInterstate 90
CountyBig Horn County
StateMontana
Coordinates45.73697, -107.57331
Functional classRural Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation3: Basically intolerable, requiring high priority of corrective action
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating17.9 US tons
Inventory rating13.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+2 approach)
Design loadHS 20
Structure length594 ft (180.9 m)
Longest span196 ft (59.7 m)
Deck width44 ft (13.5 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,258 (2023)
Projected traffic4,471 by 2043
Trucks18%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was IRR - I 90 over Bighorn River built?

It was built in 1971, making it 54 years old in 2025.

What condition is IRR - I 90 over Bighorn River in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in July 2023.

How much traffic does IRR - I 90 over Bighorn River carry?

About 4,258 vehicles per day (2023 count), of which roughly 18% are trucks.

How long is IRR - I 90 over Bighorn River?

The structure is 594 ft (180.9 m) long with a longest span of 196 ft (59.7 m) and a deck 44 ft wide.

Who owns IRR - I 90 over Bighorn River?

It is owned by the State Highway Agency.