A Knowledge-Based GIS Approach to the Evaluation of Design Consistency of Horizontal Alignments

Abstract

Design consistency is an important safety feature in the field of highway design. The driver will anticipate the alignment of a highway based on the highway section that he or she has already traveled, and unfamiliar elements that are introduced could cause serious safety problems. Much research has been performed and many different mathematical and empirical models have been formulated to predict and evaluate roadway design consistency. A knowledge-based expert system is combined with a Geographic Information System (GIS) to evaluate horizontal alignment design consistency on U.S. highways. The GIS was chosen because of its vast information storage and manipulation capabilities; it can store human expertise on a subject and suggest solutions to a problem. By evaluating the changes in the degree of curve for each consecutive element of the roadway, the program is able to successfully evaluate the consistency of horizontal alignment. The program shows a high success rate when tested on hypothetical roadways with known consistency ratings. It was applied successfully to an actual state highway in Delaware as well.