Abstract
Every time vehicles leave the road they are likely to collide with fixed roadside objects, such as lighting columns, signposts, etc. Traffic and highway engineers have always been faced with the difficult task of making important decisions regarding the selection and implementation of roadside safety improvements. To facilitate their decisions, a knowledge-based system has been developed. This paper describes the knowledge-based system which constitutes a significant extension of an existing model and uses system safety methodology. A fault tree depicting the process behind any single vehicle roadside accident has been implemented in a prototype program written in Prolog, which has since been refined.