M. Mohan, V. Kezhuvathodi

Pages: 75-88

Abstract
Traffic operations at unsignalized intersections are explained, based on the gap acceptance process, wherein, on the arrival of a lower priority movement at the intersection, the lag and gaps in the conflicting traffic streams are evaluated for safe completion of the intended maneuver. Hence, a precise understanding of the gap acceptance process is imperative for improvement of the operational efficiency and traffic safety, at unsignalized intersections. The focus of this research is to model gap acceptance characteristics at three-legged intersections, under heterogeneous traffic conditions. The prototype was developed from data collected at three locations of similar geometry. The decision to accept lag and gap was found to vary with the size and type of vehicle offering it. The model displayed good coherence, when it was validated against a segment of the collected data that was not used for model development. The investigation also discusses a simulation framework for three-legged unsignalized intersection, based on the proposed gap and lag acceptance models. Inputs required for this program included the composition of the subject and opposing traffic streams, their mean rate of arrivals, and average speed of different types of vehicles. The simulation program was validated by comparison of its output with the observed drivers’ decision on acceptance of a lag or gap. The results appear quite promising, indicating that the approach followed in this study could be further extended to simulate gap acceptance behavior at other types of street intersections.
Keywords: gap acceptance; unsignalized intersection; modelling; simulation