METHODOLOGY TO ANALYZE DRIVER DECISION ENVIRONMENT DURING SIGNAL CHANGE INTERVALS: APPLICATION OF FUZZY SET THEORY

During a signal change interval, most drivers must decide whether to stop or go based on uncertain information on speed, the remaining yellow time, and distance from the intersection. The decision process under fuzzy information, such as this case, is suited for analysis by fuzzy set theory. Fuzzy set theory and its logic has been used to analyze the driver's decision between "stop" and "clear" during the signal change interval. Fuzzy sets of "not safe stopping" and "not safe clearing" are defined along the approach roadway. Depending on the way the two sets intersect, the dilemma, indecision, or option zones can be represented. Possibility and necessity measures of "safe stopping" and "safe clearing" were defined, and they were assumed to represent the decision criteria of aggressive and conservative drivers, respectively. Based on these measures, a new approach to determine signal change intervals is suggested. It states that an interval should be such that, at any point along the approach, the possibility of "safe stopping" or "safe clearing" are always one, and the necessity measure of the two sets should exceed a certain minimum value.