INCOPORATING SIMPLE GRADE SEPARATION STRUCTURES INTO HIGHWAY ALIGNMENT OPTIMIZATION

This study develops a model that can suitably analyze simple grade separations within highway alignment optimization processes. Since grade separation structures inherently involve bridge structures, it is inevitable to take bridges into account. At least seven search methods for alignment optimization have been considered. Among them genetic algorithms are used for optimal search of the best alignment. Cost function formulations for simple grade separations, which are reasonably sufficient for preliminary highway alignment optimization but not for micro designs, are developed. A case study to evaluate adaptability and applicability of the proposed methods is conducted. The obtained solution showS that the developed methods can successfully find reasonable and acceptable solutions, thus overcoming serious weaknesses of existing alignment optimization methods that neglect characteristics of simple grade separation structures on highways.