The Control of traffic flow systems using fuzzy logic

Keywords: Fuzzy Logic, Linguistic, FuzzyControl can be used as an alternative in order to control traffic problem. The traffic problem consists of coming and going lane, junction, traffic jam and traffic light. In this study, fuzzy control has three inputs. First input is average traffic density while green light is on. Second input is average traffic density while red light is on. Third input is time of variation. There are three membership functions which show traffic density for red and green light. There are low, medium, high. Red light, green light and time of variation are defined in terms of second; this assumption is chosen because theory of problem and rule table can be easily established. In this study, an application has been carried out on Atatürk Boulevard at Adapazarı. In this application, period of light changing was assumed as a base; light changing time which can be determined beforehand and sensor which changes lights were included theoretically. Observation data which are produced by classic closed loop system were used. As shown in this study, the purpose of choosing fuzzy control is that it achieves better performances in terms of traffic flow and cost than classic and mathematical algorithm. An important advantage of fuzzy control can be observed in an unsteady traffic density case. Fuzzy control changes traffic lights in order to achieve maximum passing instead of predetermined fixed light changing time. As a result, waiting time will be less and moving time will be long. In addition to the above advantages of fuzzy control, it controls a traffic model which continuously changes. It is going to be used repeatedly because of this characteristic. This advantage can be a reason to prefer fuzzy control. In addition, repeatedly using reduces also cost of the traffic control. Time of light in the current traffic control is based on statistical data in most of the classical approaches. But, fuzzy control determines firstly the number of cars around junction and then it changes traffic signal. Therefore, results will be much better particularly under a changeable traffic density conditions. In this study, an experiment has been carried out on the junction which has five roads on Atatürk Boulevard at Adapazarı. As a result of this experiment, period of red and green light are equal to 33 and 18 consequently. These results have two advantages. First of them, time of traffic flow will be increased because period of red and green light are increased. Second of them, increment of traffic flow reduces waiting time while red light is on, so that cost of the system (approximately 50%) will be less.