US Bridges

Old Darby RD over Bitterroot River 074

Fair

Ravalli County, Montana · 5M N Darby · Structure no. L41600000+01001

Built
1917
108 years old, rebuilt 2001
Condition
Fair
inspected June 2023
Type
Truss - Thru
Steel
Length
164 ft
1 main span
Daily traffic
289
2023 count
Owner
County
County Highway Agency

About this bridge

Old Darby RD over Bitterroot River 074 is a steel truss - thru carrying Old Darby RD over Bitterroot River 074 in Ravalli County, Montana. It was built in 1917 and reconstructed in 2001, so it is 108 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 289 vehicles a day, projected to reach 328 by 2043. The structure is 164 ft (50 m) long and 15 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesOld Darby RD
CrossesBitterroot River 074
Location5M N Darby
RouteCounty Highway 41600
CountyRavalli County
StateMontana
Coordinates46.09248, -114.17561
Functional classRural Minor 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.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating47 US tons
Inventory rating28 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckWood or timber
Main spans1
Design loadH 20
Structure length164 ft (50 m)
Longest span160 ft (48.8 m)
Deck width15 ft (4.7 m)
Roadway width14 ft (4.4 m)
Vertical clearance over deck15 ft (4.6 m)

Traffic and service

Average daily traffic289 (2023)
Projected traffic328 by 2043
Trucks0%
Lanes on structure1
Traffic directionOne-lane bridge for two-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty 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 Old Darby RD over Bitterroot River 074 built?

It was built in 1917, making it 108 years old in 2025. It was reconstructed in 2001.

What condition is Old Darby RD over Bitterroot River 074 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 Old Darby RD over Bitterroot River 074 carry?

About 289 vehicles per day (2023 count).

How long is Old Darby RD over Bitterroot River 074?

The structure is 164 ft (50 m) long with a longest span of 160 ft (48.8 m) and a deck 15 ft wide.

Who owns Old Darby RD over Bitterroot River 074?

It is owned by the County Highway Agency.