Date of Award
Doctor of Philosophy
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. Although a pavement as outlined above is not yet entirely feasible, continual effort from every stakeholder with a vision of achieving sustainable development is essential for the future of society. 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. Based on the review of information, 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. Although various tools are available, like social LCA (SLCA), for evaluating the social impact of products, there is no tool available for assessing the social impact of pavements. A detailed review of published literature revealed that LCCA, LCA, and SLCA are different from each other regarding computational effort, input requirements, outputs generated, and employed assessment methodology. Most of the research has focused on one particular approach rather than an integrated approach. Additionally, each tool is at a different level of advancement, which means the required data and analytical methods may still be in the developmental stage.
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. Although researchers proposed performing social LCA, it was given low significance in sustainable assessments of pavements. The reasons for ignoring social impacts can be attributed to the unavailability of raw data (due to politics, geography, culture, etc.) or complexity of integrating (i.e., measuring, aggregating, and comparing) society-wide impacts, and lack of a standard methodology.
One more major area that is barely addressed in sustainable pavements is decision-making. The concept of sustainability is multi-criteria and multi-dimensional and requires the involvement of experts from various fields to be part of the decision-making process. Additionally, the sustainability tools provide a different output that makes decision-making process even more challenging. Since sustainability needs to be evaluated regarding economic, environmental, and social criteria, the group decision becomes a complex and often fuzzy problem. The review of information suggested that the integrated decision-making process for designing sustainable pavements has not been developed yet.
Based on the above discussion and literature review, 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 Î±- Particle Swarm Optimization (PSO) technique. The proposed decision model requires fewer inputs from decision-makers compared to conventional AHP. The advanced group decision model integrates the individual expert decisions into a group decision by maximizing the satisfaction of experts in the group and generates a clear solution.
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. A procedure for estimating the environmental impacts, during scheduled maintenance operations, due to traffic delays was developed. Earlier researchers often overlooked this phase which can have a significant impact. In this study, more emphasis was given to Life Cycle Impact Assessment (LCIA) where the environmental emissions are converted into meaningful impacts. Guidance was provided for conducting LCIA, and a new method for normalization and weighting steps of LCIA was suggested. As this Dissertation incorporated the three assessments, it opened an opportunity to understand the intertwined relations between each method, which helped to fill some research gaps.
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. In this study, an approach for performing LCA-S (social LCA) was proposed by combining principles of LCA with stakeholder management. Also, this study also placed particular emphasis on identifying and quantifying possible social impact indicators to provide decision-makers an insight on differentiating various pavement designs at the designing and planning phases.
One such social indicator that can be reasonably quantified is traffic noise. There are multiple sources of traffic noise like the engine, exhausts, tire pavement interaction, etc. Out of these sources, traffic noise due to tire pavement interaction is predominant in highways, and each pavement surface generates a different level of traffic noise. The traffic noise levels can influence real estate values, reduce neighborhood social interaction, and can have adverse health effects which may lead to a relocation of residents. Hence, traffic noise can be a potential and significant differentiating factor for pavement design selection. Even though it is a fact that traffic noise can have severe adverse social impacts, there is no existing pathway to quantify the effects. Hence, this study suggested an indirect approach for estimating the impacts. 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. FHWAâ??s Traffic Noise Model (TNM) Version 2.5 can be used to estimate the future traffic noise due to different pavement surfaces and also for estimating the noise wall barrier heights.
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 estimated 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 height of wall required to maintain noise levels below threshold levels at 100 feet from the edge of the pavement was analyzed. 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 expertâ??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.
Received from ProQuest
Inti, Sundeep, "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" (2016). Open Access Theses & Dissertations. 670.