Research on the Movement Characteristics of Unbalanced Bidirectional Passenger Flows on the Stairs in Subway Station

The interaction between bidirectional pedestrians on the stairs constitutes a potential risk for unsafe movements. This study addressed the impact of imbalanced bidirectional flows on the efficiency of pedestrian movement in subway station stairs. Research involved eight sets of controlled experiments, simulating pedestrian flow under different densities and imbalance scenarios. Different stages of bidirectional flow (pre-intersection S1, intersection S2, and after-intersection S3) were further delineated. Fundamental diagrams and Y-offset were used to describe the characteristics. The results show that the average density peaks in the S2 stage but has a shorter duration in balanced flow conditions. In S1 stage, the velocity showed a decreasing trend. In S2 stage, in medium and high densities, there are trends of velocity decreasing and then increasing, with significantly higher velocity in balanced flow. In S3 stage, evacuation velocity slows down in medium- and high-density conditions. In balanced flow conditions, Y-offset is relatively stable.