Three-Dimensional Highway Alignment Optimization for Brookeville Bypass

The Highway Alignment Optimization (HAO) model developed by our research team has been extensively refined since 1996. This paper demonstrates the applicability of the latest version of the HAO model to a real highway project with due consideration to issues arising in real-world applications. It is applied to a project for finding a suitable bypass route for a current congested segment of MD 97 (Georgia Avenue) in Brookeville, Maryland. For optimal search of the proposed bypass route, a Geographic Information System (GIS) and Genetic Algorithm (GA) are implemented in the HAO model. The integrated GA-GIS HAO model enables it to deal with numerous factors considered in road construction, using dynamic data exchange between GA and GIS while optimizing the alignment. It is found that the optimized solutions differ depending on various input specifications, such as the design speed, cross-section spacing, and tradeoff values for the environmental sensitive area. The analysis results indicate that (1) optimized alignments with varying degrees of user preferences can be efficiently found with the HAO model; and (2) the HAO model can provide early-stage design checks to minimize expensive design and operational changes in later stages. The paper concludes with a discussion of future works for further enhancement of the HAO model.