Mechanical response of dense pedestrian crowds to the crossing of intruders

NICOLAS, ALEXANDRE; KUPERMAN, MARCELO; IBAÑEZ, SANTIAGO; BOUZAT, SEBASTIÁN; APPERT-ROLLAND, CÉCILE

Scientific Reports

Nature Research

Lugar: Londres; Año: 2019 vol. 9

The increasing number of mass events involving large crowds calls for a better understanding of thedynamics of dense crowds. Inquiring into the possibility of a mechanical description of these dynamics,we experimentally study the crossing of dense static crowds by a cylindrical intruder, a mechanicaltest which is classical for granular matter. The analysis of our experiments reveals robust features inthe crowds? response, comprising both similarities and discrepancies with the response of granularmedia. Common features include the presence of a depleted region behind the intruder and the short-range character of the perturbation. On the other hand, unlike grains, pedestrians anticipate theintruder?s passage by moving much before contact and their displacements are mostly lateral, hencenot aligned with the forces exerted by the intruder. Similar conclusions are reached when the intruderis not a cylinder, but a single crossing pedestrian. Thus, our work shows that pedestrian interactionseven at high densities (3 to 6 ped/m 2 ) do not reduce to mechanical ones. More generally, the avoidancestrategies evidenced by our findings question the incautious use of force models for dense crowds.