The location of roadside objects: an expert system to assess the safety aspects

The paper concerns the development of an expert system to assist a traffic or highway engineer when making decisions about the location of roadside objects (lighting columns, signposts etc.). It illustrates how system safety techniques can be applied to a transportation safety problem. Fault tree analysis is used to represent the process behind single vehicle accidents. A simple fault tree is then implemented as a demonstration expert system. The probabilities for each basic event, namely those at the bottom of the fault tree, are estimated then combined according to the logic of the tree in order to compute the probability of a single vehicle accident. The effect on the probability of a single vehicle accident of eliminating, relocating, protecting or using other forms of roadside object can be explored with the demonstration expert system, making use of the diagnostic facilities offered by Prolog. The result should eventually be a quantitative design tool