Using life cycle thinking approach to support environmental sustainability in big linear infrastructure projects: Alignment modelling, optimization and evaluation for reducing impacts to the natural environment

Abstract

This thesis focuses on environmental optimization of the vertical alignment in large linear infrastructure projects, at early design stage. Two categories of problems are investigated: “modification of the existing alignment” and “generation of a new alignment”. The road is modelled with fixed geometrical parameters. Several models are developed which relate the road gradients, for each constituting segment of the road, to three elements retained as influential factors in this study i.e. the earthwork cost, the energy cost and the emission cost. Two concepts are introduced to support the constructed methods: the “single level approach (SLA)” and the “multi-layered multi-level approach (MLMLA or ML2A)”. These approaches are based on the performances of test vehicles used as a proxy for characterizing the environmental profile of vertical alignments of linear infrastructures. New metrics for evaluating the performances of the vertical alignments are also introduced based on the life cycle assessment method. The final models of the vertical alignment have implemented piece-wise linearity using lower order spline polynomial techniques to decrease complexity level and maintain robustness. This enables the use of simple linear programming techniques for solving (optimizing) the developed models. The methods have been implemented in MATLAB (for the first problem type) and Python (for the second problem type) environments. Models’ performances are illustrated through simulations and application to real world cases, and validation is performed through benchmarking with results from similar studies found in the literature. Higher and lower gradient limits, powertrains and standard technologies, speed levels, load factors, and vehicle segment have all been investigated throughout this project. It is shown that the developed models can successfully be used to design vertical alignments with reduced environmental impacts, and that several other factors that influence the performance of heavy-duty vehicles on highways need to be considered.