Decision Support Rules for Profile Design at Intersections

Abstract

This research addresses the development of heuristic decision support rules to aid highway designers in designing intersection profiles that reduce the degree of roughness in the design. Six heuristic rules are developed for six common types of at-grade intersections. When provided with the elevation difference between the secondary roadway and the main highway for intersection construction, the heuristic suggests the values of curve parameters that can provide a feasible profile design with acceptable level of roughness, and generates the elevation points representing the profile. The roughness computation method used in the heuristic rules is validated using real-life examples. Profiles generated by the proposed heuristics are also compared with randomly generated feasible designs. Data comparison using t-test shows that the heuristic rules can generate profiles with significantly lower roughness measured with the International Roughness Index than can randomly generated feasible profiles.