Investigating the influence of conflicting flow’s composition on critical gap under heterogeneous traffic conditions

Abstract

The choice to accept or reject an available gap at unsignalized intersections depends on several factors that include driver and vehicle characteristics, intersection geometry, weather conditions, etc. Although drivers in heterogeneous traffic conditions accept shorter gaps than their counterparts in developed countries, they are reluctant to accept the same gap offered by a large-sized vehicle instead of a smaller vehicle. This influence of traffic stream’s composition on the critical gap is not well-established. The present research attempts to quantify this influence by realizing its importance, especially under heterogeneous traffic conditions. Data were collected from six unsignalized intersections located in different parts of India through videography. Details about gaps and lags which were accepted and rejected, types of vehicles involved in the gap acceptance process, and the amount of conflicting traffic faced by each of the turning vehicles were extracted from the recorded videos. Critical gaps for different vehicle types making right-turns at each of the intersections were estimated based on Occupancy Time Method. Further, a non-linear regression revealed that the estimated critical gaps vary logarithmically with the percentage of large-sized vehicles in the conflicting flows. Based on these relationships, the base values of the critical gap and the adjustment for the proportion of large-sized vehicles in conflicting flows are estimated for turning movements at unsignalized intersections in heterogeneous traffic conditions. These relationships will be useful in assessing the capacity of unsignalized intersections of developing countries.

Keywords

• Critical gap
• Unsignalized intersection
• Driver behaviour
• Heterogeneous traffic
• Occupancy time method