Effect Of U Turns On Capacity Reduction At Signalized Intersection

Abstract

Right turn movements have been considered as one of the major resources of traffic operations and safety problems in the roadway system. Approaches used to achieve control of right turns includes separation of the right turns in exclusive right turning lanes, use of U turns either at or after the intersection and consolidation of median opening. The concept of U turns as an alternative to direct right turn movements is a relatively new approach and has recently been implemented in several locations. The safety gain from such a design is due to decrease in the number of conflicting points at the intersection. This study analysed the effect of U turning vehicles on the right turn saturation flow rate. Data regarding queue discharge time and U turning vehicles were taken at three signalized intersections in Trivandrum city, Kerala, India. Based on the data collected, a second degree polynomial regression model was developed which estimated the relationship between average queue discharge time for each turning vehicle and varying percentage of U turning vehicles. Adjustment factors for varying percentages of U turning vehicles were also developed by using the regression model. The adjustment factor developed in this study was used in estimating the capacity reduction due to varying percentage of U turning vehicles at signalized intersection.