Mechanical response of dense pedestrian crowds to the crossing of intruders

Alexandre Nicolas,Marcelo Kuperman,Santiago Ibañez,Cécile Appert-Rolland,Sebastián Bouzat

doi:10.1038/s41598-018-36711-7

Abstract

The increasing number of mass events involving large crowds calls for a better understanding of the dynamics 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 mechanical test which is classical for granular matter. The analysis of our experiments reveals robust features in the crowds’ response, comprising both similarities and discrepancies with the response of granular media. 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 the intruder’s passage by moving much before contact and their displacements are mostly lateral, hence not aligned with the forces exerted by the intruder. Similar conclusions are reached when the intruder is not a cylinder, but a single crossing pedestrian. Thus, our work shows that pedestrian interactions even at high densities (3 to 6 ped/m2) do not reduce to mechanical ones. More generally, the avoidance strategies evidenced by our findings question the incautious use of force models for dense crowds.

Highlights

Magritte’s surrealistic painting Golconda depicts a suburban landscape with scores of passers-by stiffly standing in mid-air, as if they were ‘raining’ over the city
Predictions for pedestrian flows are of great avail for the architectural design of large facilities and for the management of throngs, whether it be in underground stations[1], at mass religious events[2] or sports gatherings[3], or in front of a shop just before its opening on Black Fridays in the United States
The fear of stampedes in such assemblies has turned much of the research effort on dense crowds towards extreme situations, such as past crowd disasters[2,4] or scenarios of evacuation through a door[5,6,7,8], but at high densities complex collective phenomena are expected in ordinary situations and require proper modelling

Summary

Introduction

Magritte’s surrealistic painting Golconda depicts a suburban landscape with scores of passers-by stiffly standing in mid-air, as if they were ‘raining’ over the city. The outputs of simulations made with commercial software have been compared to some high-density real-life situations[9,10,11], but such comparisons are generally restricted to macroscopic observables - for example evacuation times - and visual impressions. We aim to (i) collect controlled experimental data on dense crowds that can be used to test and calibrate models, (ii) explore the similarities of the crowd’s response to the intrusion of a cylinder with that of granular media, and (iii) discuss the case in which the intruder is a single pedestrian, a situation often encountered in daily-life. We lay the first stone for the empirical development of the (continuum) mechanics of dense crowds

Objectives

Methods

Results

Conclusion