Robust spatial self-organization in crowds of asynchronous pedestrians

Abstract

AbstractSimilar to other animal groups, human crowds exhibit a variety of self-organized collective behaviors. Spontaneous formation of unidirectional lanes in bidirectional pedestrian flows is one of the most striking examples of self-organization in human crowds. In addition, previous experimental studies have suggested that stepping among pedestrians is spontaneously synchronized over time. However, those studies have primarily focused on one-dimensional, single-file crowds, limiting our understanding of temporal stepping patterns in crowds with more freedom of movement and their relationship to spatial patterns of organization. Here, we conducted experiments of bidirectional pedestrian flows (24 pedestrians in each group) and investigated the relationship between collective footsteps and self-organized lane formation by tracking each individual trajectory as well as foot-stepping kinematics. We found that, unlike previous studies, pedestrians did not spontaneously align their steps unless there was an external auditory cue to follow. Moreover, we found that footstep synchronization generated by external cues disturbed the flexibility of pedestrians’ lateral movements, increased potential collision risks, and narrowed the formed lanes, suggesting structural instability in the spatial organization. These results imply that, without external cues, pedestrians marching out of step with each other can efficiently self-organize into robust structures. Understanding how asynchronous individuals contribute to ordered collective behavior has potential applications for promoting efficient crowd management and will inform theoretical models for human and other animal collective behavior with asynchronous positional updates.