Experimental study on the decision-making and motion behavior of subgroups when facing a static obstacle during movement

Abstract

The interaction between pedestrians and obstacles is an interesting research topic in pedestrian and evacuation dynamics. Many studies on this topic have treated single individuals or human crowds as objects and have drawn a lot of research findings. However, as an intermediate layer linking the individual and group levels, subgroups have rarely been considered in such studies, and little is known about their behavioral mechanisms when interacting with obstacles. From this, we want to understand how certain key factors affect the decision-making and motion behavior of subgroups when facing a static obstacle during movement. Here, we organize a series of controlled experiments, in which the obstacle width, time pressure, and subgroup size serve as three control variables to create various experimental conditions. The analysis of the experimental data shows that a wider obstacle width, a more urgent time pressure, and a larger subgroup size correspond to a higher proportion of the splitting–merging state. The strong right-side preference emerges in the maintaining state, but the movement preference in the splitting–merging state largely depends on the difference in subgroup sizes. The path lengths in the splitting–merging state are longer than those in the maintaining state, but no significant difference exists in movement times between the two movement states. The conclusion that the average speeds decrease with increasing subgroup size at normal densities can be extended to most conditions of different obstacle widths, time pressures, and movement states. Besides, the three control variables have various influence degrees on centroid positions, movement times, and average speeds in the splitting and merging processes, and the herding effect of subgroup members can be observed in the merging process. Overall, these findings may advance the understanding of subgroup behaviors and support the development of subgroup models.