Mechanical response of dense pedestrian crowds to the crossing of\n intruders

Abstract

The increasing number of mass events involving large crowds calls for a\nbetter understanding of the dynamics of dense crowds. Inquiring into the\npossibility of a mechanical description of these dynamics, we experimentally\nstudy the crossing of dense static crowds by a cylindrical intruder, a\nmechanical test which is classical for granular matter. The analysis of our\nexperiments reveals robust features in the crowds' response, comprising both\nsimilarities and discrepancies with the response of granular media. Common\nfeatures include the presence of a depleted region behind the intruder and the\nshort-range character of the perturbation. On the other hand, unlike grains,\npedestrians anticipate the intruder's passage by moving much before contact and\ntheir displacements are mostly lateral, hence not aligned with the forces\nexerted by the intruder. Similar conclusions are reached when the intruder is\nnot a cylinder, but a single crossing pedestrian. Thus, our work shows that\npedestrian interactions even at high densities (3 to 6 ped/m 2) do not reduce\nto mechanical ones. More generally, the avoidance strategies evidenced by our\nfindings question the incautious use of force models for dense crowds.\n