US Bridges

I 94 over Sian Hill Road

Fair

Yellowstone County, Montana · 6.2M E Pompeys Pillar · Structure no. I00094029+02432

Built
1976
49 years old
Condition
Fair
inspected October 2024
Type
Slab
Concrete Continuous
Length
79 ft
3 main spans
Daily traffic
2,255
2023 count
Owner
State
State Highway Agency

About this bridge

I 94 over Sian Hill Road is a concrete continuous slab carrying I 94 over Sian Hill Road in Yellowstone County, Montana. It was built in 1976, so it is 49 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 2,255 vehicles a day, roughly 30% of them trucks, projected to reach 2,367 by 2043. The structure is 79 ft (24.1 m) long and 44 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI 94
CrossesSian Hill Road
Location6.2M E Pompeys Pillar
RouteInterstate 94
CountyYellowstone County
StateMontana
Coordinates46.01403, -107.87444
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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating46 US tons
Inventory rating36 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length79 ft (24.1 m)
Longest span30 ft (9.1 m)
Deck width44 ft (13.5 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,255 (2023)
Projected traffic2,367 by 2043
Trucks30%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesOther
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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I 94 over Sian Hill Road built?

It was built in 1976, making it 49 years old in 2025.

What condition is I 94 over Sian Hill Road 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 October 2024.

How much traffic does I 94 over Sian Hill Road carry?

About 2,255 vehicles per day (2023 count), of which roughly 30% are trucks.

How long is I 94 over Sian Hill Road?

The structure is 79 ft (24.1 m) long with a longest span of 30 ft (9.1 m) and a deck 44 ft wide.

Who owns I 94 over Sian Hill Road?

It is owned by the State Highway Agency.