Genetic algorithm model for optimizing horizontal alignments of a two-ramp interchange

The work of highway geometric design is very complicated and consumes significant amount of labor, time and cost. For the design of the horizontal alignments of a double-lined highway system, the design demands greater complexity because the relativities of the two alignments in the system need to be considered simultaneously. Due to the design complexity, it is thorny to get a feasible solution to meet all code requirements manually for engineers, let alone to systematically search for better designs. In order to reduce the design cost and enable automatic computerized design, it is necessary to develop mathematical models to look for the optimized geometric design for of the horizontal alignments of a double-lined highway system. This research focuses on solving the problems inhering in the horizontal alignments of a double-lined highway system. By analyzing the basic elements for the horizontal alignment of the ramp and cumulating the regularity of the basic elements between two inflection points, it is possible to define several new ramp elements. Then, a model is built up based on the genetic algorithm developed by redefining the new basic elements for horizontal alignments according to the variation of the partial curvature radius. The advantage of the proposed method is to get a good solution under all constrains in the design of the horizontal alignment for a two-ramp interchange system.