Which Method is Appropriate- INAFOGA or PROBABILITY EQUILIBRIUM for Critical Gap Estimation of U-turn Vehicles at Median Openings In Urban Indian Context

Abstract

Over the past few years there has been increased installation of non-traversable un-signalized median openings in most of the urban regions in India. The motive behind this installation is to eliminate problems associated with illegal U- turns at intersections and other traffic facilities close to the median openings on multi-lane urban roads. Data collected for this study is in the form of video-images of six U-turn median openings on 4-lane and 6-lane roads situated in the cities of Bhubaneshwar, Rourkela and Ranchi located in the eastern part of India. This paper introduces a new concept on merging behavior of U-turn vehicles for evaluation of gaps accepted by drivers at median openings based on the INAFOGA method; which is further compared with the critical gap values obtained by and Macroscopic Probability Equilibrium concept for heterogeneous traffic flow in the urban region of the Indian states. IBM-SPSS 22.0 has been used to perform a paired-sample Hypothesis (t-test) between these two methods which reveal that critical gap values obtained by INAFOGA are 18-31% more than those obtained by Probability Equilibrium method. Radar plots, box-plots, t- statistic, two-tailed significance value coupled with higher critical gap values for different modes of transport (except Sport Utility Vehicles) validates the fact that INAFOGA method is indeed appropriate under mixed traffic conditions. This observation on influence area of gap acceptance at median openings using the merging behavior concept has given sufficient clue to carry out further research on critical gaps at roundabouts or interchanges.