US Bridges

I 15 over Int Jackson-Hwy 278

Fair

Beaverhead County, Montana · 3.7M S Dillon · Structure no. I00015059+07111

Built
1982
43 years old
Condition
Fair
inspected November 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
128 ft
3 main spans
Daily traffic
2,863
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Int Jackson-Hwy 278 is a prestressed concrete stringer/multi-beam or girder carrying I 15 over Int Jackson-Hwy 278 in Beaverhead County, Montana. It was built in 1982, so it is 43 years old, younger 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 2,863 vehicles a day, roughly 23% of them trucks, projected to reach 3,120 by 2043. The structure is 128 ft (39 m) long and 44 ft wide.

Location

Open in Google Maps
CarriesI 15
CrossesInt Jackson-Hwy 278
Location3.7M S Dillon
RouteInterstate 15
CountyBeaverhead County
StateMontana
Coordinates45.17928, -112.69307
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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionNovember 2023
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 rating52 US tons
Inventory rating29 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length128 ft (39 m)
Longest span65 ft (19.8 m)
Deck width44 ft (13.4 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,863 (2023)
Projected traffic3,120 by 2043
Trucks23%
Lanes on structure2
Traffic directionOne-way traffic
CarriesOverpass structure at an interchange
CrossesHighway
Detour if closed—
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 15 over Int Jackson-Hwy 278 built?

It was built in 1982, making it 43 years old in 2025.

What condition is I 15 over Int Jackson-Hwy 278 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 November 2023.

How much traffic does I 15 over Int Jackson-Hwy 278 carry?

About 2,863 vehicles per day (2023 count), of which roughly 23% are trucks.

How long is I 15 over Int Jackson-Hwy 278?

The structure is 128 ft (39 m) long with a longest span of 65 ft (19.8 m) and a deck 44 ft wide.

Who owns I 15 over Int Jackson-Hwy 278?

It is owned by the State Highway Agency.