Modeling Gap-Maintenance in Heterogeneous No Lane-Discipline Traffic

Abstract

Traffic stream of developing countries have a characteristic heterogeneous traffic stream moving in a weak or no lane-discipline. Due to these reasons, state-of-the-art car-following models cannot replicate vehicular interactions in developing countries. Car-following behavior is in a staggered fashion, with following gap changing as per amount of stagger, vehicle type of leading and following vehicles as also their speeds. The aim of this paper is to determine the variation in longitudinal gap as staggering or centerline separation, and speed changes, for different leading and following vehicle pairs moving in a heterogeneous traffic stream. A top view video of moving traffic is recorded with accurate field markings. Twelve mid-block sections in cities of India are selected for this purpose; each having ideal roadway conditions and varying widths and flow levels. Camera calibration technique of vanishing point method is adopted for extracting vehicle pairwise trajectory data from different sections. From these data, leading and following vehicle sizes, their speeds, types are noted along with longitudinal gap, centerline separation between them. Data are processed for finding relationships, and model is calibrated and validated. It is seen that longitudinal gap increases with decrease of centerline separation and increase of speed. The graphs change for varying vehicle types and speed ranges. Established relationships can be used for modeling gap-maintenance characteristics in heterogeneous traffic.