Lane formation mechanism in public health risk scenarios: An empirical study on bidirectional pedestrian flow

Lane formation is a self–organized phenomenon that emerges spontaneously in bidirectional pedestrian flow. Exploring the mechanisms leading to lane formation in public health risk scenarios is critical for managing both mass events and daily pedestrian transportation. This study explores bidirectional flow through experiments and investigates the mechanisms behind the emergence of spontaneous lane formation, focusing on two opposing groups walking in a mock corridor in public health risk scenarios. The flow ratio was varied by adjusting the group sizes while keeping the total flow and density constant. Pedestrian trajectory data were tracked and analyzed to identify five phases of lane formation, which included the spontaneous creation and dissolution of lanes. To characterize these dynamics, we used fundamental diagrams and analyzed metrics such as order parameters, lane entropy, exposure time, and angular momentum. Our results show that, in public health risk scenarios, bidirectional flow leads to intense interactions and local turbulence, which inhibits lane formation. Notably, when the prescribed social distance (PSD) is set to 1.5 m and 2.0 m, the exposure times and probability density function (PDF) peak values show minimal differences across different cases, indicating that a PSD of 1.5 m is sufficient to enhance lane formation. Furthermore, the identification of angular momentum fluctuations reveals that pedestrian movements are predominantly concentrated between 16.0 s and 23.0 s, while the PDF indicates a rightward rotational bias in avoidance behavior, leading to symmetry breaking in the chiral system. Our findings provide new insights into pedestrian self–organization in risk environments and have practical implications for urban pedestrian flow management.