Optimization of pavement preservation strategy considering cost and environmental impacts
Creators: name: Al-Saadi, Israa Fadhil Jasim
Publisher: name: No Publisher Supplied
Year: 2018

description: Road maintenance is crucial for the purpose of retarding deterioration of pavement, which is a complex and continuous process due to the interaction of heavy traffic, environmental condition, and material aging. The combination of increased traffic and lack of appropriate maintenance causes a higher rate of degeneration in the roads. Transportation agencies need to develop a system for disseminating limited funds and decide the timing to conduct maintenance and repairs. In order to establish a cost-effective budget and achieve the optimum utilization of available resources, the agency needs to decide which maintenance treatment to use and where and when to apply it.  The primary objective of this dissertation is to develop network-level pavement preservation decisions considering multiple objectives of cost and environmental impacts. This research will produce multi-objective optimization models designed to provide highway agencies with means of making road maintenance decisions among different concerns. Therefore, this study developed regression models of CO2 emissions for four vehicle types to quantify the environmental impact at the use stage.   The simulated constraint boundary method (SCBM) was used as a tool to find Pareto optimal solutions for the pavement multi-objective optimization problem of minimizing agency costs and minimizing CO2 emissions by minimizing average network IRI value. This method is based on solving one objective and converting the other objective to constraint, so the decision makers need to decide first which objective should be considered as the primary objective (the objective that deserves the most attention among the competing objectives). The results show that the crack seal is still the most dominant preservation treatments compared to thin overlay although it has less effect on the reduction of IRI than the thin overlay treatment. So, the objective of minimizing agency cost controls the optimization results although the minimization of CO2 emissions was considered in the optimization process.  Another method that was used in this research to achieve both objectives of minimizing agency costs and emissions is the Weighted Sum method. Weighted sum method is based on converting the two objectives into one single objective by adding both objectives together after multiplying each objective by a weighting factor. The value of weighting factor should be considerable relative to other weighting factors and comparative to its corresponding objective function. The results for the distribution of pavement preservation treatments show that less costly preservation treatments were selected for the most segments of the network when the priority of optimization was given to the objective of minimization agency cost. The treatments that have higher effectiveness on pavement condition were selected for the most segments of the network when the objective of minimization CO2 emission is the main objective compared to the other objective.