Traffic Dynamics of Vehicles Passing Each Other on Bidirectional Undivided Narrow Roads

Abstract

<p>This study investigates traffic dynamics on bidirectional undivided narrow roads. A novel heuristic-based passing (HP) model is proposed to microscopically model the complex passing maneuvers. Considering both perceived visual stimuli and steering imprecision, the model incorporates two heuristics that determine the driving direction and speed in the navigation of the most direct but unobstructed route. Real-world experiments analyzing the passing process of two vehicles on undivided narrow roads with varying widths were conducted. The results reveal that vehicles decelerated, veered toward the roadside to facilitate an oncoming vehicle’s passage and then readjusted to the center of the road, providing empirical support to the proposed HP model. In addition, as the road width increased, both the passing speed and clearance distance increased. The calibrated HP model could replicate the trajectories of the passing vehicles, demonstrating its accuracy. Real-world field observations were made at two undivided roads of varying widths and opposing traffic densities to investigate the macroscopic traffic patterns under the influence of lateral friction. The results showed that, on the undivided narrow road, when the traffic density in the travel direction was relatively low, the presence of high-density opposing traffic significantly reduced the speed of vehicles in the travel direction. Moreover, the proposed microscopic HP model well replicated the macroscopic traffic flow patterns. Overall, the results of this study enhance the understanding of traffic dynamics in the passing process on undivided narrow roads, offer insights for local road geometric design, and help identify sources of congestion evolution.<br></p>