Experimental study on the impact of visibility on bidirectional pedestrian flow under high and low urgency conditions

Bidirectional pedestrian flow often leads to significant casualties and property damage when out of control, especially in emergencies. This study aims to investigate the characteristics of bidirectional pedestrian flow evacuation under different visibility and urgency conditions. Bidirectional pedestrian evacuation experiments are conducted under three different visibility conditions and two levels of urgency. The evacuation behavioral patterns are analyzed, including typical evacuation behaviors, evacuation speeds, and evacuation time of bidirectional pedestrian flows. Overtaking behavior, following behavior and boundary fast effect are observed during the evacuation process. As visibility decreased, pedestrian evacuation speeds also declined. The reduction in pedestrian speed due to diminished visibility was more pronounced under high-urgency conditions compared to low-urgency scenarios. Compared with non-emergency situations, in emergency situations, the moving speeds of pedestrians moving in the opposite direction are 61.90 %, 34.62 %, and 26.25 % faster when they are not wearing eye-patches, wearing an eye patch with a light transmittance of 27 %, and wearing eye-patches with a light transmittance of 16 %, respectively. The results highlight the critical impact of visibility on evacuation efficiency in emergencies. These findings provide empirical data on the influence of visibility and urgency level on emergency evacuation performance and offer valuable insights for crowd management.