APPLICATION OF FUZZY LOGIC TO TRAFFIC SIGNAL CONTROL UNDER MIXED TRAFFIC CONDITIONS

摘要

Traffic signal control is commonly used at road intersections to minimise vehicular uddelay. Fixed time control shows good results in conditions where there is a little fluctuation in udtraffic demand, however in time-varying traffic fixed time control becomes inflexible and udinefficient. This may produce traffic congestion and lead to increased delays and air pollution. udDemand responsive traffic signal control must be introduced to overcome these problems. udHowever, all the available demand responsive traffic signal control methods such as udVehicle Actuated Controller (VAC), Traffic Optimisation Logic (TOL), Microprocessor udOptimised Vehicle Actuation (MOVA) and Fuzzy Logic Traffic Signal Controllers (FLTSC) have udbeen developed for non-mixed traffic conditions, considering only motor vehicles move in udclearly defined lanes, neglecting motorcycles. These demand responsive traffic signal controls udare not appropriate for the mixed traffic conditions of developing countries such as Indonesia, udwhere the traffic streams consist of different types of vehicle with a wide variation in their udstatic, dynamic and operating characteristics, and with a particularly high proportion (30% - ud70%) of motorcycles. Also there is lack of lane discipline. udThis thesis describes the design and evaluation of an adaptive traffic signal controller based on udfuzzy logic for an isolated four-way intersection with specific reference to mixed traffic in uddeveloping countries, including a high proportion of motorcycles. Four proposed controllers udhave been developed for different schemes. The controllers were designed to be responsive to udreal time traffic demands. The study identifies two traffic parameters as appropriate as input uddata for an adaptive traffic signal controller under mixed traffic conditions such as the proposed udFLTSC: the average occupancy rate (%) and maximum queue length (metres). The literature udstudy suggest that this data should be collected using advances video image processing. The udproposed FLTSC uses maximum queue lengths and average occupancy rates collected during the udprevious cycle to estimate the number of seconds of green time required by each set of signal udgroups during the next cycle. udThe effectiveness of the proposed FLTSC was analysed using the microscopic traffic udsimulation model VISSIM. Prior to doing so, the VISSIM model was calibrated and validated. udFrom the validation process it was apparent that the VISSIM model could be adapted to simulate mixed traffic conditions by use of the Packet approach. In this approach, motorcycles udare modelled as a group of motorcycles. udThe performance of the proposed FLTSC was contrasted with a Fixed Time Controller ud(FTC) for different case studies on a simulated four-way intersection. The FTC is represented by udthe calculation as suggested in the Indonesian Highway Capacity Manual. Separate analysis udusing TRANSYT show that this is a valid assumption to make. The simulation results show that udthe proposed FLTSC is generally better than the FTC in terms of the average delay of vehicles at udan intersection, especially under time-varying traffic. udFurther analysis was carried out to compare the performance of the proposed FLTSC udagainst a Vehicle Actuated Controller (VAC) for different traffic conditions on a simulated four-udway intersection, East-West and North-South without turning movements. In order to analyse udthe performance of VAC, a refined VISSIM model was developed. This used the latest version of udthe VISSIM software and allowed individual vehicles (and particularly motorcycles) to be udmodelled in mixed traffic. udThe phase extension time is one of the most critical parameters to affect the overall udperformance of VAC (Bullen, 1989). To provide a fair comparison of the performance between udthe proposed FLTSC and the VAC, an investigation was carried out to find the most appropriate udextension time for the VAC that was suitable for mixed traffic. The effect of motorcycles to the udperformance of the VAC was also investigated. Two schemes were carried out to observe it, udnamely: Scheme 1 where detector detects all vehicle types (DfT, 2006) and Scheme 2 where uddetector detects all vehicle types, apart from motorcycles. udThe simulation results show that the VAC System D (DfT, 2006) using an extension time udof 1.2 seconds and the VAC Extension Principle (Kell and Fullerton, 1991) with a detector udposition of 30 metres and extension time of 3.0 seconds produced better performance than the udother extension times tested for both schemes in terms of the average delay of vehicles. This is udslightly shorter than current practice in developed countries. udThe simulation results indicate that the performance of the VACs with scheme 1 is udgenerally worse than with scheme 2. The performance of the VACs with scheme 1 against udscheme 2 tended to reduce significantly as the percentage of motorcycles in traffic increased. udThe study compares the effectiveness of FTC, VAC Extension Principle (VAC-EP), VAC System udD (VAC-SD) and proposed FLTSC in various traffic conditions. The simulation results indicate udthat the average delay of the proposed FLTSC is close to the average delay of the FTC when used udin cases with constant traffic flows but sometimes worse. However, in cases of time-varying udtraffic the proposed FLTSC is superior to the FTC. When comparing the simulation results of the udproposed FLTSC, VAC-SD and VAC-EP, again the proposed FLTSC does not improve average uddelay, when traffic flows constant but produces better results in cases of time-varying traffic. ud