US Bridges

I 15 over Sep County Road

Fair

Toole County, Montana · 1M S Shelby · Structure no. I00015362+01852

Built
1976
49 years old
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
75 ft
1 main span
Daily traffic
1,520
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Sep County Road is a prestressed concrete stringer/multi-beam or girder carrying I 15 over Sep County Road in Toole 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 1,520 vehicles a day, roughly 29% of them trucks, projected to reach 1,596 by 2043. The structure is 75 ft (22.9 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 15
CrossesSep County Road
Location1M S Shelby
RouteInterstate 15
CountyToole County
StateMontana
Coordinates48.49988, -111.88365
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.
Superstructure8 Very GoodNo problems noted.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionAugust 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating46 US tons
Inventory rating23 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length75 ft (22.9 m)
Longest span75 ft (22.9 m)
Deck width44 ft (13.5 m)
Roadway width41 ft (12.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,520 (2023)
Projected traffic1,596 by 2043
Trucks29%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
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 15 over Sep County Road built?

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

What condition is I 15 over Sep County 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 August 2024.

How much traffic does I 15 over Sep County Road carry?

About 1,520 vehicles per day (2023 count), of which roughly 29% are trucks.

How long is I 15 over Sep County Road?

The structure is 75 ft (22.9 m) long with a longest span of 75 ft (22.9 m) and a deck 44 ft wide.

Who owns I 15 over Sep County Road?

It is owned by the State Highway Agency.