Date of Award

5-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Civil Engineering

Advisor

Dr. Mashrur Chowdhury

Committee Member

Dr. Bradley J. Putman

Committee Member

Dr. Weichiang Pang

Committee Member

Dr. Margaret Wiecek

Abstract

Facing an exceptional challenge of maintaining state roadways with ever-shrinking financial resources, this research examined multiple facets of the impact of overweight trucks. The objectives of this research were to investigate the impact of overweight trucks on pavements and bridges, and develop policy recommendations based on technical analysis and the modern political and institutional environment in South Carolina. To achieve the objectives, this research modeled pavement and bridge deterioration, investigated the adequacy of standard practices in state agencies, examined how trucking industry perceives those practices, and developed policy analysis models. Pavement and bridge deterioration analysis revealed that pavement and bridge damages increase significantly with incremental weights. Combined bridge and pavement damage costs per mile for different overweight truck types were estimated in this research. User fees to recover damage costs for overweight vehicles are of five basic structures: flat, distance based, weight based, weight and distance based, and axle based. To recover additional costs of damage imparted by overweight trucks for load in excess of the legal weight limits in an axle based fee structure, damage fee will vary between $24 and $175 per trip for different overweight truck types, while a flat fee structure will charge all overweight trucks $65 per trip (including $10 adminstrative permit processing fee). Consideration of axle load, axle configuration and trip length in the fee structure will reflect damage imparted by each overweight truck more accurately. Under the current fee structure, overweight trucks in South Carolina pay $30 for a single trip permit, and $100 for an annual permit which is equivalent to 3.33 trips. An Ohio DOT study found that with an annual permit, on average, 24.8 trips were made by an overweight truck. This research applied a multiobjective analysis approach to address conflicting objectives, and to generate detailed tradeoffs between different overweight truck damage cost recovery fee options. This research presents a case study with two objectives: 1) minimization of unpaid pavement and bridge damage by overweight freight trucks, and 2) minimization of overweight damage cost recovery fees. The tradeoff analysis reveals that increasing the flat overweight damage cost recovery fee by $1 from $43 will reduce unpaid damages by $4.2 million in year 2012 in South Carolina with a high elasticity of demand. In the axle-based damage cost recovery fee type, increasing the average axle-based overweight damage cost recovery fee by $1 from $43 will reduce unpaid damages of $3.8 million in year 2012 in South Carolina. These types of tradeoff analyses provide valuable information to decision makers in selecting an appropriate type and level of fee for overweight trucks. Interviews with overweight trucking stakeholders in South Carolina did not reveal any common consensus on how overweight permit polices should be refined. Stakeholders expressed their concern that increasing permit fee will surge illegal overweight trips. It is critical to develop effective enforcement plan to deter illegal overweight trucks before implementation of new fee policies. As consensus does not exist among stakeholders, SCDOT must establish a working group with all interested parties to understand everyone's concerns before proposing any new policies. User fees to recover damage costs for overweight vehicles are of five basic structures: flat, distance based, weight based, weight and distance based, and axle based. To recover additional costs of damage imparted by overweight trucks for load in excess of the legal weight limit in an axle based fee structure, damage fee will vary between $24 and $175 per trip for different overweight truck types, while a flat fee structure will charge all overweight trucks $65 per trip (including $10 adminstrative permit processing fee). Consideration of axle load, axle configuration and trip length in the fee structure will reflect damage imparted by each overweight truck more accurately. Under the current fee structure, overweight trucks in South Carolina pay $30 for a single trip permit, and $100 for an annual permit which is equivalent to 3.33 trips. An Ohio DOT study found that with an annual permit, on average, 24.8 trips were made by an overweight truck. This research applied a multiobjective analysis approach to address conflicting objectives, and to generate detailed tradeoffs between rational overweight truck damage cost recovery fee options. This research presents a case study with two objectives: 1) minimization of unpaid pavement and bridge damage by overweight freight trucks, and 2) minimization of overweight damage cost recovery fees. The tradeoff analysis reveals that increasing the flat overweight damage cost recovery fee by $1 from $43 will reduce unpaid damages by $4.2 million in year 2012 in South Carolina with a high elasticity of demand. In the axle-based damage cost recovery fee type, increasing the average axle-based overweight damage cost recovery fee by $1 from $43 will reduce unpaid damages of $3.8 million annually in South Carolina. These types of tradeoff analyses provide valuable information to decision makers in selecting an appropriate type and level of fee for overweight trucks. While South Carolina's trucking stakeholders contributing their perspectives to this research did not reveal consensus on how overweight fees in the state should evolve, but some common points did emerge from interviews. Representatives of well-intentioned shipping companies expressed concern that raising fees will encourage illegal trucking without permits, and the effectiveness of enforcement is nationally unclear. Enforcement planning must coincide with a revision of South Carolina's overweight fees. Other considerations should include effects of overweight fee policies across jurisdictions and consistency in the mega-region. SCDOT and trucking industry representatives should 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.

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