A decision making approach for selection of sustainable pavements in Texas by integrating life cycle cost analysis (LCCA), life cycle assessment (LCA) of environmental and social impacts

A sustainable pavement can be defined as the one that minimally impacts future economic opportunities, social conditions, human health, and the environment and still fulfills the engineering objectives. In this study, one such effort was initiated by proposing a framework for selection of pavement design based on sustainable development. The concept of sustainability is widely believed to be founded on three criteria: economic, environmental, and social standards. Since the purpose of pavements it to provide service for many decades, assessing each criterion throughout the life of pavements is required, that is, based on life cycle assessments. The most widely used economic evaluation tool for pavements is Life Cycle Cost Analysis (LCCA), which has been proposed by the Federal Highway Administration (FHWA). Practitioners have started using Life Cycle Assessment (LCA) recommended by the International Organization for Standardization (ISO), which has been recently adopted by the FHWA to estimate environmental impacts. There is no tool available for assessing the social impact of pavements. LCA provides the necessary information for decision-makers in selecting pavement designs, which minimally impacts the environment. However, it is observed that it has never been fully utilized in selecting pavement design and construction. The reasons might be due to a lack of standardized and validated databases for assessments, unavailability of well-defined methodologies to assess impacts during some phases of pavement, and also transforming the environmental impacts into meaningful data understandable to civil engineers. One more major area that is barely addressed in sustainable pavements is decision-making. Since sustainability needs to be evaluated regarding economic, environmental, and social criteria, the group decision becomes a complex and often fuzzy problem. It was concluded that the design and selection of sustainable pavements would require an integrated decision-making process. A tool for evaluating the social impact of pavements, filling in the LCA database gaps and evaluation approaches, and a systematic approach for comparing alternate pavement designs; thus, this dissertation is aimed to achieve the same. A multi-criterion group decision model was proposed in this study by combining the Analytic Hierarchy Process (AHP), the Data Envelopment Analysis (DEA) based preference aggregation method, and the α- Particle Swarm Optimization (PSO) technique. The proposed decision model requires fewer inputs from decision-makers compared to conventional AHP. This study also contributed towards filling some of the deficits in life cycle assessments. This study identified models and databases that are reliable and applicable to LCA of pavements and are accessible to practitioners. The selection of pavement design based on social sustainability principles is also often ignored due to the complexity involved in the quantification of social issues (like violation of labor rights), throughout the life cycle of pavements. One such social indicator that can be reasonably quantified is traffic noise. Noise barrier walls are commonly constructed to reduce traffic noise levels to below the thresholds. Since various pavements generate different levels of traffic noise, each pavement type needs an accurate height of barrier wall to keep the traffic noise at acceptable levels. The construction costs and emissions associated with building and maintenance of barrier walls can be used to make a decision. In the end, the proposed framework and developed methodologies were demonstrated through a fictional case study. Four pavement designs were developed to perform for 30 years. The design software and inputs required for various assessments were selected for the state of Texas. LCCA, LCA, LCA-S were performed for analyzing the impacts for 30 years. Within LCCA, agency costs for constructing and maintaining highways for 30 years was estimated. Also, expenses incurred to users during maintenance operations was estimate under user costs. In LCA, ten air pollutants were assessed and then transformed into six impact categories. In LCA-S, traffic noise was calculated without barrier walls for 30 years and then barrier wall analysis was performed to keep the noise at acceptable levels. The life cycle costs (construction and maintenance) of barrier walls was estimated and categorized as social costs. Similarly, the LCA was performed for barrier walls and six impact categories were classified as social emissions. A decision-making template using traditional AHP was developed and eight experts from various fields like construction management, execution, environment, policy-making, etc. , were asked to provide their judgments. Six experts chose Design 4 as the preferred and two experts chose Design 1. The group decision was generated based on the expert’s individual inputs, and the group decision was in favor of Design 4. Even though this dissertation delivered an integrated framework for selecting sustainable designs, it needs to be further enhanced by including the overlooked parameters. The framework needs to be validated by applying it to a real highway project. (Abstract shortened by ProQuest. )