Traffic congestion on urban roads has become a serious concern, particularly, at intersections. The performance of an intersection controls the performance of urban roads meeting at that intersection. The paper presents the effect of addition of turning lane in the middle of approach road at busy signalized at-grade intersection, narrowing the width of all lanes to keep total road width the same, in heterogeneous traffic. The traffic at intersection comprises both of vehicles and pedestrians. Their interactions along with signal cycle decide the efficiency of an intersection. A microscopic simulation tool VISSIM, has been used to model the heterogeneous (mixed) traffic under constraints of roadway geometry, vehicle characteristics, driving behaviour and traffic controls. The effect is investigated with different random seeds to obtain reasonable results for analysis. The performance evaluation is done in terms of vehicle throughput, average queue length, maximum queue length, average delay time per vehicle, average speed and emission of Carbon monoxide CO, mono-nitrogen oxides NOx, Volatile organic compounds (VOC) etc. It has been observed that on adding turning lane in the middle, of approach road the average queue length, maximum queue length, average delay time per vehicle and emission per vehicle get considerably reduced, while there is an increase in vehicle throughput and average speed of all the vehicles. The results reported in this paper clearly shows that addition of turning lane in existing intersection can reduce congestion considerably, enhancing performance of intersections and network.
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