DESIGN AND SIMULATION OF A FUZZY LOGIC TRAFFIC SIGNAL CONTROLLER FOR A SIGNALIZED INTERSECTION

Abstract

Traffic control and management poses a major problem in many cities, especially in rapidly growing and motorizing cities like Nairobi, Kenya. Currently, fixed-cycle controllers are being used in all signalized intersections in Nairobi. This has culminated in most intersections within the city almost grinding to a halt during peak hours. The efficiency of traffic flow through an intersection depends on the phases, sequence and the timing of the traffic signals installed.  This paper proposes a fuzzy logic system to control traffic signals on a signalized intersection. The Fuzzy Logic Controller (FLC) dynamically controls the traffic light timings and phase sequence to ensure smooth flow of traffic, decrease traffic delays and thus increase the intersection capacity. In the design, vehicle detectors are placed strategically upstream and downstream to determine traffic density and the delay on each approach. This traffic data is then used by the FLC to determine whether to extend or to terminate the current green phase and to select the appropriate phase sequence.   A fuzzy logic traffic control simulation model is developed and tested using MATLAB/ SIMULINK software. The performance of the Fuzzy Logic traffic controller is then compared to that of the fixed-cycle controller. The performance of FLC is found to be similar to that of the fixed controller in normal traffic conditions. However, in heavy traffic conditions, FLC results shows 25% decrease on average delay of cars waiting at the intersection and 6% improvement on total number of cars served at the intersection over the same simulation period compared to the fixed cycle controller. The results show that there is a huge improvement that can be realized by using FLC in controlling traffic flow at intersections.