GAP ACCEPTANCE BEHAVIOR OF RIGHT-TURNING VEHICLES AT T-INTERSECTIONS - A CASE STUDY

SYNOPSIS This paper deals with the study of the gap acceptance of major to minor road and minor to major road right turning vehicles at limited priority T-intersections in India (vehicles are driven on the left side in India). The unsignalized intersections in India are uncontrolled or partially controlled; analyzing such intersections is complex. Limited priorities are observed at partially controlled intersections, where major and minor roads are perceived by drivers based on intersection geometry and traffic volume and speed on the approaches.Field data were collected at four T-intersections with limited priority using video camera. The data extracted include gap/lag, subject vehicle type, conflicting vehicle type, and driver’s decision (accepted/ rejected).Different distributions are fitted to the available and accepted gaps. Based on Kolmogorov-Smirnov (K-S) test, it is found that gamma distribution fits the available gaps well, whereas accepted gaps are better represented with lognormal distribution. Binary logit models are developed for gap acceptance for the both turning movements. For model development, 80% of the extracted data (total data observations are 722 for major road right turning vehicles and 1066 for minor road right turning vehicles) are used and remaining are used for model validation. The percentage of correct prediction by binary logit models are 74.48% (for major road right turning) and 81.51% (for minor road right turning).Critical gaps estimation revealed that maximum likelihood method gives the most consistent results. The critical gaps are smaller than the values reported for developing countries.