I 93 SB BT 38-46
over TR ORANGE LINE
.7 MI N OF JCT I93&US1, Suffolk County, Massachusetts
Condition
FairYear Built
1970
Daily Traffic
87,100
Length
65 ft
About This Bridge
I 93 SB BT 38-46 carries traffic over TR ORANGE LINE in Suffolk County, Massachusetts. Built in 1970, this structure is 56 years old, placing it among the older bridges still in active service. The bridge features steel construction with a girder and floorbeam design, a combination chosen by engineers to meet the specific requirements of this crossing.
Approximately 87,100 vehicles cross this bridge daily, making it a high-traffic corridor critical to regional transportation. Bridges carrying this volume require enhanced inspection schedules and proactive maintenance programs. Commercial trucks account for 6% 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 fair condition based on federal inspection criteria established by the Federal Highway Administration. The structure meets current safety standards for its designated use and load capacity. With a total length of 65 feet, this is a shorter span typical of local road crossings, often carrying traffic over small streams, drainage channels, or other roadways.
Steel bridges provide high strength-to-weight ratios, making them suitable for longer spans. However, they require ongoing protection against corrosion through painting or weathering steel designs. Inspectors pay close attention to connection points, fatigue cracking, and coating condition.
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
Deck Condition
Satisfactory
Superstructure
Satisfactory
Substructure
Fair
Channel & Protection
N/A
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 fair condition rating of 5 indicates some deterioration that warrants monitoring but doesn't affect structural integrity.
For a structure built in 1970, this condition level is expected given the bridge's age and usage patterns. High traffic volumes on a bridge in fair or poor condition typically elevate its priority for rehabilitation or replacement in state transportation planning.
Bridge Details
Steel 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 4,173 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.
87,100
Avg Daily Traffic (2016)
Vehicles per day crossing this bridge
6%
Truck Traffic
Commercial vehicle percentage
113,868
Projected Future ADT
Estimated future demand
This bridge carries approximately 87,100 vehicles per day, translating to roughly 31,791,500 crossings annually. This high volume places significant demands on the structure and necessitates frequent inspections.
Commercial trucks comprise 6% 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 113,868 vehicles daily, a 31% 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
5.0 tons
Maximum allowable load for special permits
Inventory Rating
3.0 tons
Load level for normal traffic
The operating rating of 5.0 tons represents the absolute maximum load this bridge can carry under controlled conditions with special permits. The inventory rating of 3.0 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
Data: 2020-2024 FHWA National Bridge Inventory
Location
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43.235556, -71.702222
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.