Simultaneous optimization of vertical and horizontal road alignments

Optimization of three-dimensional road alignments is recognized as a nonlinear and nonconvex optimization problem. The development of models that fully optimize a three-dimensional road alignment problem is not yet successful, because there are many factors involved and complexities in the geometric specification of the alignment. At present, there are two optimization approaches, the models that simultaneously optimize horizontal and vertical alignments, and those employing two or more stages of optimization processes. In this thesis, we develop a novel approach of solving a three dimensional road alignment problem where the optimal horizontal and vertical alignments are determined simultaneously. We develop the surrogate cost model that approximate the earthwork cost and the pavement cost. The problem is modelled as a multiobjective optimization where the cost due to the length of the road, and the cost due to the volume of earthwork are found to be conflicting objectives. In order to study the proposed model, two case studies are tested and the numerical results are provided. The experimental results indicate that the problem is nonconvex, and that it is, indeed, a multiobjective optimization problem. Further developments and improvements in the area of cost penalty parameters are recommended for future work.