Investigation of Crossing Conflicts by Vehicle Type at Unsignalized T-Intersections under Varying Roadway and Traffic Conditions in India

Abstract

The study attempts to investigate crossing conflicts at unsignalized T-intersections under mixed traffic conditions using post encroachment time (PET) as a surrogate safety measure (SSM). To comprehend the objective, data for four unsignalized T-intersections with varying intersection geometry (with and without Central Island) was collected using videography techniques. Primarily, PET datasets were extracted in the lab from the recorded video and were checked for their probability distributions. Among all the potential distributions, generalized extreme value (GEV) distribution was observed to be the best-fitted distribution. Further investigations revealed that the percentage of critical crossing conflicts (PCCC) was higher with the presence of motorized two-wheelers (2W) and motorized three-wheelers (3W) in the traffic stream. This was followed by cars, buses, LCVs, and trucks. Among vehicle type combinations (conflicting-offending), 2W-2W, 2W-3W, 3W-2W, and 3W-3W were identified as the most critical cases for the subject study locations. Further, it was observed that the volume of conflicting stream and proportion of 2Ws in the conflicting stream has a significant effect on PCCC. The obtained PCCC, when compared among the subject study locations for similar traffic flow characteristics, revealed a significant difference between them, highlighting the effect of intersection geometry on traffic safety. The severity of conflicts was delineated into four levels by correlating PET values with the speed of conflicting vehicles. The developed severity levels, compared with the field-recorded crash data are found to be in close approximation. This establishes PET as a valid SSM.