Multi-objective optimization of greenhouse gas emissions in highway construction projects

With the increasing interest in relationships between built environments and ecosystems, the environmental impacts of the construction industry have been a subject of many studies. Based on the results of previous studies using construction systems modeling and life cycle assessment, the authors treated greenhouse gas (GHG) emissions as an additional project objective to time and cost, and applied multi-objective optimization to derive optimal solutions for transportation projects. Two highway construction case studies were analyzed for relationships between time, cost and environmental impacts. The results showed strong positive correlation between time and cost, moderate positive correlation between cost and GHG emissions, and weak positive correlation between time and GHG emissions. The results suggest that it is less likely that time and GHG emissions may affect each other. It is more so to time and GHG emissions. In addition, it is unlikely that there are common factors that can simultaneously affect cost and GHG emissions, or time and GHG emissions. Future studies are needed to include other types of environmental impacts and further understand the advantages and disadvantages of the lack of dependency between time and GHG emissions, as well as cost and GHG emissions in order to enhance sustainable construction.