Parametric Estimation of U-Turn Vehicles at Median Openings in Urban Indian Context

Abstract

The purpose of capacity modelling at U-turns is to develop a relationship between capacity and and its geometric characteristics. In fact, the few models available for the estimation of capacity at different transportation facilities does not provide specific guidelines at median openings. For this reason, an effort is made to estimate the capacity by collecting the data sets from median openings at different lane roads of Hyderabad City, India. Wide difference (43% -59%) among the capacity values estimated by the existing models shows the limitation to consider for the mixed traffic situations. Thus, a new model is proposed for the estimation of the capacity of U-turn vehicles at median openings considering mixed traffic conditions which would further prompt to investigate the effect of different factors that might affect the capacity. In order to estimate the critical gap of U-turn vehicles, recently developed method ‘INAFOGA’ which is based on clearing behavior of drivers at un-signalized intersections is modified and applied considering the merging behaviour of U-turn vehicles at median openings and named as ‘Modified INAFOGA’ method. Modified INAFOGA method is compared with probability equilibrium method through paired-sample hypothesis (t-test) and result revealed that difference in mean values 0.009 signifies that both methods are comparable. Difference in critical gap values obtained from the box plots and radar charts indicates that Probability equilibrium method is not suitable to address the behavior of U-turn vehicles at median openings under mixed traffic conditions and these observations validates the fact that ‘modified INAFOGA’ method is indeed appropriate under mixed traffic conditions. Follow up time is estimated by measuring the time gap between two successive U-turn vehicles which are being queued to take a U-turn. The estimation of capacity model proposed in this paper is simple, easy to implement and suitable to mixed traffic conditions.