US Bridges

Old HWY 10 over Bighorn River 126

Fair

Yellowstone County, Montana · 4M E Custer · Structure no. L56104002+05001

Built
1930
95 years old
Condition
Fair
inspected July 2023
Type
Truss - Thru
Steel
Length
629 ft
2 main spans
Daily traffic
100
2025 count
Owner
State
State Highway Agency

About this bridge

Old HWY 10 over Bighorn River 126 is a steel truss - thru carrying Old HWY 10 over Bighorn River 126 in Yellowstone County, Montana. It was built in 1930, so it is 95 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 5 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 100 vehicles a day, roughly 3% of them trucks, projected to reach 100 by 2040. The structure is 629 ft (191.8 m) long and 21 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesOld HWY 10
CrossesBighorn River 126
Location4M E Custer
RouteCounty Highway 81017
CountyYellowstone County
StateMontana
Coordinates46.14729, -107.46731
Functional classRural Local

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating36.9 US tons
Inventory rating22.9 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans2 (+2 approach)
Design loadH 15
Structure length629 ft (191.8 m)
Longest span275 ft (83.8 m)
Deck width21 ft (6.4 m)
Roadway width20 ft (6.1 m)
Vertical clearance over deck15 ft (4.6 m)

Traffic and service

Average daily traffic100 (2025)
Projected traffic100 by 2040
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

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

Frequently asked questions

When was Old HWY 10 over Bighorn River 126 built?

It was built in 1930, making it 95 years old in 2025.

What condition is Old HWY 10 over Bighorn River 126 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 Old HWY 10 over Bighorn River 126 carry?

About 100 vehicles per day (2025 count), of which roughly 3% are trucks.

How long is Old HWY 10 over Bighorn River 126?

The structure is 629 ft (191.8 m) long with a longest span of 275 ft (83.8 m) and a deck 21 ft wide.

Who owns Old HWY 10 over Bighorn River 126?

It is owned by the State Highway Agency.