S 200
over CLARK FORK RIVER
1M W THOMPSON FALLS, Sanders County, Montana
Condition
PoorYear Built
1960
Daily Traffic
2,436
Length
95 ft
About This Bridge
S 200 carries traffic over CLARK FORK RIVER in Sanders County, Montana. Built in 1960, this structure is 66 years old, placing it among the older bridges still in active service. The bridge features steel continuous construction with a girder and floorbeam design, a combination chosen by engineers to meet the specific requirements of this crossing.
Approximately 2,436 vehicles cross this bridge daily, indicating lower traffic volumes common for local roads and rural routes. While traffic is lighter, these bridges still serve essential community transportation needs. Commercial trucks account for 3% of all crossings. This proportion of commercial traffic is typical for this roadway classification and is factored into the bridge's design load ratings.
The bridge is currently rated in poor condition based on federal inspection criteria established by the Federal Highway Administration. It is classified as structurally deficient, meaning one or more components have received a rating of 4 or below on the 0-9 scale. This designation indicates significant deterioration that warrants attention, though the bridge remains safe for travel within its posted limits. Structurally deficient does not mean unsafe—rather, it signals that repairs or replacement should be prioritized in transportation planning. With a total length of 95 feet, this is a shorter span typical of local road crossings, often carrying traffic over small streams, drainage channels, or other roadways.
The construction materials used in this bridge were selected based on engineering requirements, cost considerations, and local conditions at the time of construction.
Federal law requires that all highway bridges be inspected at least every 24 months by qualified inspectors following the National Bridge Inspection Standards (NBIS). Some bridges with known issues or unusual characteristics may be inspected more frequently. Inspection data is reported to the National Bridge Inventory, a database maintained by the Federal Highway Administration that tracks the condition of all public highway bridges in the United States. This bridge data is sourced from that federal database and reflects the most recent available inspection results.
Condition Ratings
Structurally Deficient
This bridge has one or more component ratings of 4 or below, indicating significant deterioration that requires attention. The bridge remains safe for travel but may have load restrictions.
Deck Condition
Poor
Superstructure
Poor
Substructure
Satisfactory
Channel & Protection
Good
Lowest Rating
Determines condition category
NBI condition ratings range from 0 (failed) to 9 (excellent). Ratings of 4 or below are considered poor. The overall condition category is determined by the lowest individual component rating.
The deck rating of 4 indicates advanced deterioration affecting the driving surface. The superstructure rating of 4 shows advanced deterioration in beams or girders.
For a structure built in 1960, the current condition reflects the cumulative effects of age, traffic, and environmental exposure. If this bridge were closed, traffic would face a detour of approximately 124 miles, underscoring the importance of maintaining this crossing.
Bridge Details
Steel Continuous is the primary structural material, which influences maintenance requirements and expected lifespan. The girder and floorbeam design was selected based on span requirements, load capacity needs, and site conditions at the time of construction. Maintenance responsibility falls to State Highway Agency.
Construction
Dimensions
Span dimensions affect structural design choices and load distribution. The deck area of 2,816 sq ft determines surface maintenance scope.
Classification
Status
Traffic Data
Traffic volume data helps engineers assess bridge wear patterns and plan maintenance schedules. Average Daily Traffic (ADT) counts are updated periodically and represent typical weekday usage.
2,436
Avg Daily Traffic (2022)
Vehicles per day crossing this bridge
3%
Truck Traffic
Commercial vehicle percentage
2,558
Projected Future ADT
Estimated future demand
This bridge carries approximately 2,436 vehicles per day, translating to roughly 889,140 crossings annually. Lower traffic volumes generally result in less structural wear over time.
Commercial trucks comprise 3% of traffic. Heavy vehicles cause disproportionate wear—a single fully loaded truck can have the impact of thousands of passenger cars on bridge deck surfaces.
Traffic projections estimate future volumes of 2,558 vehicles daily, a 5% increase from current levels. These projections inform capacity planning and potential upgrade requirements.
Load Ratings
Load ratings determine what weight this bridge can safely support. These values are critical for routing heavy vehicles and issuing overweight permits.
Operating Rating
4.7 tons
Maximum allowable load for special permits
Inventory Rating
2.9 tons
Load level for normal traffic
The operating rating of 4.7 tons represents the absolute maximum load this bridge can carry under controlled conditions with special permits. The inventory rating of 2.9 tons is the safe load limit for everyday traffic without restrictions. These relatively low ratings may result in posted weight limits or route restrictions for heavy vehicles.
5-Year Condition Trend
↓DecliningCondition has declined by 1.0 rating points since 2020
Status Changes
- Entered poor condition in 2021
- Became structurally deficient in 2021
Data: 2020-2024 FHWA National Bridge Inventory
Location
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48.062222, -116.167222
Identification
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Data Source: Federal Highway Administration (FHWA) National Bridge Inventory 2024
Bridge inspection data is typically updated every 24 months. Conditions may have changed since the last inspection.
“Structurally deficient” does not mean a bridge is unsafe or likely to collapse. It indicates that one or more key structural elements are in poor or worse condition. Bridges are inspected regularly and may have load restrictions in place.
This data is for informational purposes only and should not be used for route clearance or vehicle weight decisions.