EVALUATING THE DESIGN CONSISTENCY OF HORIZONTAL ALIGNMENT BY KNOWLEDGE-BASED GEOGRAPHIC INFORMATION SYSTEMS

Design consistency is an important design feature in the field of highway design. The driver will anticipate the alignment of a highway based on the highway section he/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. In this paper, 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 for this project because of its vast information storage manipulation capabilities, and the expert system for its ability to store human expertise on a subject and suggest solutions to a problem. By evaluating the changes in the degree of curvature 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, and is successfully applied to the state of Delaware as well.