LA0315

over BAYOU DULARGE

.01 MI NORTH OF LA 661, Terrebonne Parish, Louisiana

Condition

Fair

Year Built

1977

Daily Traffic

12,596

Length

231 ft

About This Bridge

LA0315 carries traffic over BAYOU DULARGE in Terrebonne Parish, Louisiana. Built in 1977, this structure is 49 years old, placing it among the older bridges still in active service. The bridge features steel construction with a movable - bascule design, a combination chosen by engineers to meet the specific requirements of this crossing.

Approximately 12,596 vehicles cross this bridge daily, representing moderate traffic volumes typical of important regional connectors. This level of usage requires regular monitoring to ensure continued safe operation. Commercial trucks account for 11% 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 231 feet, this structure falls within the typical range requiring standard inspection procedures conducted by certified bridge inspectors.

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

6

Deck Condition

Satisfactory

6

Superstructure

Satisfactory

7

Substructure

Good

8

Channel & Protection

Very Good

6

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 6 indicates satisfactory condition with minor section loss or deterioration.

For a structure built in 1977, this condition level is expected given the bridge's age and usage patterns.

Bridge Details

Steel is the primary structural material, which influences maintenance requirements and expected lifespan. The movable - bascule 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

Year Built1977
MaterialSteel
Design TypeMovable - Bascule
OwnerState Highway Agency

Dimensions

Total Length231 ft (70.4 m)
Max Span15 ft (4.6 m)
Deck Width4 ft
Deck Area8,453 sq ft

Span dimensions affect structural design choices and load distribution. The deck area of 8,453 sq ft determines surface maintenance scope.

Classification

Route TypeState Highway
Route Number315
Lanes On Bridge2
Lanes Under Bridge2

Status

Toll BridgeNo
Historical SignificanceNot eligible
Scour Critical8
Detour Length1 mi (2 km)

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.

12,596

Avg Daily Traffic (2021)

Vehicles per day crossing this bridge

11%

Truck Traffic

Commercial vehicle percentage

13,855

Projected Future ADT

Estimated future demand

This bridge carries approximately 12,596 vehicles per day, translating to roughly 4,597,540 crossings annually. This moderate traffic level is typical for regional connectors.

Commercial trucks comprise 11% 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 13,855 vehicles daily, a 10% 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

4.3 tons

Maximum allowable load for special permits

Inventory Rating

2.9 tons

Load level for normal traffic

The operating rating of 4.3 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

Stable

Condition has remained relatively stable since 2020

Data: 2020-2024 FHWA National Bridge Inventory

Location

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29.626944, -90.819722

Identification

Structure Number025502459009801
NBI IDLA-025502459009801
State FIPS22
County FIPS109

Explore More

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.

LA0315 over BAYOU DULARGE | Louisiana