Unraveling human crowd dynamics through the foot tracking of pedestrians.

Movement of pedestrian crowds is ubiquitous in human society. However, it is unclear what dynamical regimes pedestrian crowds can exhibit at different crowd densities, how pedestrians move in these different dynamical regimes, and in which dynamical regime the movement synchronization of pedestrians is most likely to occur. Here, we conducted a unidirectional crowd movement experiment, in which we tracked the movement of pedestrian crowds through foot tracking. We find experimentally that pedestrian crowds can exhibit three distinct dynamical regimes (free regime, slow-moving regime, and jammed regime) depending on the crowd density. In the free regime, pedestrians' movement is not constrained; in the slow-moving regime, pedestrians' speed is constrained, but pedestrians' movement direction in each step is not influenced; and in the jammed regime, both pedestrians' speed and movement direction in each step are constrained. We also demonstrate that pedestrians are most likely to synchronize their movements spontaneously at the onset of jamming. Our findings provide important insights into crowd dynamics.