US Bridges

I 15 over RR

Fair

Toole County, Montana · 1M N Sunburst · Structure no. I00015390+01711

Built
1977
48 years old
Condition
Fair
inspected June 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
336 ft
5 main spans
Daily traffic
955
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over RR is a prestressed concrete stringer/multi-beam or girder carrying I 15 over RR in Toole County, Montana. It was built in 1977, so it is 48 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 955 vehicles a day, roughly 40% of them trucks, projected to reach 1,003 by 2043. The structure is 336 ft (102.4 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
CrossesRR
Location1M N Sunburst
RouteInterstate 15
CountyToole County
StateMontana
Coordinates48.88939, -111.90776
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.
Superstructure8 Very GoodNo problems noted.
Substructure7 GoodSome minor problems.
Last inspectionJune 2023
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 rating50 US tons
Inventory rating26 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans5
Design loadHS 20
Structure length336 ft (102.4 m)
Longest span77 ft (23.5 m)
Deck width44 ft (13.5 m)
Roadway width42 ft (12.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic955 (2023)
Projected traffic1,003 by 2043
Trucks40%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesRailroad
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 RR built?

It was built in 1977, making it 48 years old in 2025.

What condition is I 15 over RR 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 June 2023.

How much traffic does I 15 over RR carry?

About 955 vehicles per day (2023 count), of which roughly 40% are trucks.

How long is I 15 over RR?

The structure is 336 ft (102.4 m) long with a longest span of 77 ft (23.5 m) and a deck 44 ft wide.

Who owns I 15 over RR?

It is owned by the State Highway Agency.