US Bridges

S 446 over Yellowstone River

Fair

Rosebud County, Montana · 1M W Rosebud · Structure no. S00446001+02661

Built
1970
55 years old
Condition
Fair
inspected June 2023
Type
Girder and Floorbeam System
Steel Continuous
Length
683 ft
4 main spans
Daily traffic
257
2023 count
Owner
State
State Highway Agency

About this bridge

S 446 over Yellowstone River is a steel continuous girder and floorbeam system carrying S 446 over Yellowstone River in Rosebud County, Montana. It was built in 1970, so it is 55 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 257 vehicles a day, roughly 3% of them trucks, projected to reach 270 by 2043. The structure is 683 ft (208.2 m) long and 32 ft wide. If it were closed, the detour would be 55.3 mi (89 km).

Location

Open in Google Maps
CarriesS 446
CrossesYellowstone River
Location1M W Rosebud
RouteState Highway 446
CountyRosebud County
StateMontana
Coordinates46.27478, -106.465
Functional classRural Major Collector

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating41 US tons
Inventory rating24 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4 (+1 approach)
Design loadHS 15
Structure length683 ft (208.2 m)
Longest span173 ft (52.6 m)
Deck width32 ft (9.9 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic257 (2023)
Projected traffic270 by 2043
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed55.3 mi (89 km)
TollOn a free road
National Highway SystemNo

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—
NavigationNo navigation control on waterway

Frequently asked questions

When was S 446 over Yellowstone River built?

It was built in 1970, making it 55 years old in 2025.

What condition is S 446 over Yellowstone River 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 S 446 over Yellowstone River carry?

About 257 vehicles per day (2023 count), of which roughly 3% are trucks.

How long is S 446 over Yellowstone River?

The structure is 683 ft (208.2 m) long with a longest span of 173 ft (52.6 m) and a deck 32 ft wide.

Who owns S 446 over Yellowstone River?

It is owned by the State Highway Agency.