A Decision Support System For Optimal Selection Of Roadway Alignments Using Sustainability Metrics
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ProgramDoctor of Engineering
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Sustainability, as a long-term concern about environmental, economic, and social issues that affect the well-being of humans and environment, and the need for its implementation in engineering has been highlighted in the last few decades. New concepts such as "Green" and "Sustainable" have penetrated into most planning and engineering fields. Transportation and specifically roadways, being one of the major sources of emission, are under intense attention of environmental legislations. Roadway alignments are usually designed based on short-term cost minimization (e.g. minimization of earthwork cost). However, the need for adopting a long-term perspective in the design process that incorporates other important factors such as overall amount of fuel consumption and accident costs in the roadway lifetime is becoming self-evident. Achieving a sustainable roadway is not possible without addressing its footprint on environment, society, and economy. In this study, a decision support system is developed for evaluation and comparison of alternative geometric alignments based on their sustainability ratio determined from fuel consumption (environmental impact), safety (social impact), and earthwork (economic impact) as follows: a) Development of a Fuel Consumption evaluation model associated with roadway geometric design parameters, which evaluates and compares alternative alignments based on their fuel efficiency. b) Development of a Sight Distance evaluation model that evaluates and compares the alternative alignments safety based on their available and required sight distance profiles. c) Development of a Terrain Disturbance evaluation model that evaluates and compares the alternative alignments earthwork and minimizes the environmental impacts on natural terrain shape. The formulation for all three models is then implemented in AutoCAD Civil 3D software package (programmed in Visual Basic language) to automatically evaluate any given alignment based on these three metrics. The developed model provides the tools for designers and planners to quantitatively compare and rate various alternatives and select the optimal alignment. This model is advantageous over existing rating systems that evaluate metrics qualitatively.