Estimation of Critical Gap for U-turn Vehicles at Median openings Under Mixed Traffic Conditions

Installation of unsignalized median openings have increased in many Indian cities during the past few years due to the non-accommodation of minor movements like U-turns on unsignalized intersections. Gap acceptance behavior for U-turns vehicles is an important aspect at unsignalized median openings. Critical gap forms the sole parameter in gap acceptance models. Estimation of critical gaps for U-turns at median openings under mixed traffic conditions have not been addressed till today. Reason being the complex and risky vehicular interactions under mixed traffic at median openings. Data comprises video recording of 4 U-turn median openings in Bhubaneshwar city. In this paper, a new concept on merging behavior of U-turn vehicles for evaluation of gap acceptance has been introduced. Two existing methods namely Harders and Satish et al. “INAFOGA” are used for estimating critical gap considering four motorized modes of transport for all the four sections. Cluster plots for all four sections are shown to compare these two methods considering the four modes. A paired sample T-test was done in IBM SPSS 22.0 which revealed that “INAFOGA” method yield critical gap values 28–41% more than those obtained by Harders method. This explained the robustness of “INAFOGA” method in addressing mixed traffic conditions for U-turns at median openings.