RATE OF DETERIORATION OF BRIDGES AND PAVEMENTS AS AFFECTED BY

TRUCKS

Terry SwygertSouth Carolina Department of Transportation

Research conducted by Clemson UniversityPrincipal Investigator

Mashrur (Ronnie) Chowdhury, Ph.D., P.E., F.ASCE

High Value Research Sweet SixteenAASHTO RAC/TRB State Representatives Annual Meeting‐

July 22, 2014

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Problem Statement

Investigate the impact of heavy vehicle traffic on pavements and bridges in South Carolina

Create policy recommendations based on technical analysis and institutional environment in South Carolina

Facing an exceptional challenge of maintaining state roadways with ever-shrinking financial resources, SCDOT commissioned this study to examine multiple facets of the impact of overweight trucking. The objectives of this study were to:

This study involved the examination of both engineering and policy analysis related to overweight truck operation in South Carolina.

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Research Performed

1) Pavement Damage Estimation

2) Bridge Damage Estimation

3) Evaluation of Fee Structures

4) Policy Implementation Challenges

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Research PerformedThe researchers developed estimates for the damage costs due to the additional weight (i.e., from legal weight limit to the maximum weight limit) allowed by typical SCDOT overweight permits (2012 dollars).

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Total Per mile Damage Cost

Truck Type

Per mile damage cost by a truck loaded at the

legal weight limit

Additional per mile damage cost for additional load from the legal weight

limit to the maximum weight limit

2-axle, 35-40 kips $0.3523 $0.3225 3-axle, single unit, 46-50 kips $0.2474 $0.1459 3-axle, combination, 50-55 kips $0.4442 $0.3002 4-axle, single unit, 63.5-65 kips $0.3585 $0.1015 4-axle, combination, 65-70 kips $0.4884 $0.3363 5-axle, 80-90 kips $0.4583 $0.3837 6-axle, 80-90 kips $0.2585 $0.1822 6-axle, 90-100 kips $0.2585 $0.4249 6-axle, 100-110 kips $0.2585 $0.7538 7-axle, 80-90 kips $0.1428 $0.1128 7-axle, 90-100 kips $0.1428 $0.2528 7-axle, 100-110 kips $0.1428 $0.4452 7-axle, 110-120 kips $0.1428 $0.7012 7-axle, 120-130 kips $0.1428 $1.0302 8-axle, 80-90 kips $0.1140 $0.0865 8-axle, 90-100 kips $0.1140 $0.1919 8-axle, 100-110 kips $0.1140 $0.3528 8-axle, 110-120 kips $0.1140 $0.5357 8-axle, 120-130 kips $0.1140 $0.7890

Overweight Permit Fee Structures

Flat fee

Axle based fee

Weight based fee

Weight-distance based fee

Distance based fee 6

User fees to recover costs for overweight vehicles assessed by others were examined and found to be of five basic structures:

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Stakeholders’ Interview Participants

Organization Interest Group

Greenville Chamber of Commerce, Transportation and Infrastructure Committee

Represents business and shippers

South Carolina Trucking Association

Represents shipping companies

South Carolina State Transport Police

Represents law enforcement

South Carolina Department of Transportation

Represents interests of infrastructure maintenance

South Carolina Farm Bureau Represents the agricultural industry

Carolinas Ready-Mixed Concrete Association

Represents heavy construction materials

A heterogeneous fee collection practice was observed among states in the US.

Stakeholders do not show any consensus on how to recover additional damage due to overweight trucks.

Consideration of axle load, axle configuration and trip length would be more appropriate in setting overweight permit fees.

In a flat fee structure, some trucks would pay less, and some trucks would pay more compared to an axle based fee structure.

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RESEARCH RESULTS

RESEARCH RESULTS

To recover damage imparted by overweight trucks in South Carolina, the permit fee would vary between $24 and $175 per trip (for axle based fee structure).

In a Flat Fee structure, the permit fee would be $65 for all trucks.

There is no clear relationship between annual-permit fees and single-trip permit fees.

(includes $10 administrative permit processing fee)

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Currently South Carolina charges a flat fee of $30 for single trip permits and $100 for an annual permit

A flat annual permit is equivalent to 3.33 single trips

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IMPLEMENTATION

1) This study was commissioned by the SCDOT’s Research and Development Executive Committee (RDEC). A Presentation was made to the RDEC earlier this month which included our new Secretary of Transportation Janet Oakley.

All parties must start with a recognition that something needs to be done— VERY IMPORTANT

2) Although through the Stakeholder’s Interview Process there was not a consensus developed on possible revisions to the current overweight permits and fee structure, there was acknowledgement from some that South Carolina’s fees are low and they would be willing to take on higher fees as long as they are implemented fairly.

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IMPLEMENTATION

3) Therefore, through this study the process has begun for SCDOT and trucking industry representatives to work together in an ongoing focus group to develop common understanding of issues, consensus around objectives, and provisions for fairness that will address industry concerns.

A copy of the final report is available at the SCDOT Research Website located at http://scdot.scltap.org/

For more information, contact:

Dr. Mashrur (Ronnie) Chowdhury, P.E., F.ASCE Professor of Civil Engineering

Clemson University at mac@clemson.edu