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Traffic instabilities in self-organized pedestrian crowds



Elsa Guillot

Mathieu Moreau


Olivier Chabiron

Samuel Lemercier



Pierre Degond

Guy Theraulaz


In human crowds as well as in many animal societies, local interactions among individuals often give rise to self-organized collective organizations that offer functional benefits to the group. For instance, flows of pedestrians moving in opposite directions spontaneously segregate into lanes of uniform walking directions. This phenomenon is often referred to as a smart collective pattern, as it increases the traffic efficiency with no need of external control. However, the functional benefits of this emergent organization have never been experimentally measured, and the underlying behavioral mechanisms are poorly understood. In this work, we have studied this phenomenon under controlled laboratory conditions. We found that the traffic segregation exhibits structural instabilities characterized by the alternation of organized and disorganized states, where the lifetime of well-organized clusters of pedestrians follow a stretched exponential relaxation process. Further analysis show that the inter-pedestrian variability of comfortable walking speeds is a key variable at the origin of the observed traffic perturbations. We show that the collective benefit of the emerging pattern is maximized when all pedestrians walk at the average speed of the group. In practice, however, local interactions between slow- and fast-walking pedestrians trigger global breakdowns of organization, which reduce the collective and the individual payoff provided by the traffic segregation. This work is a step ahead toward the understanding of traffic self-organization in crowds, which turns out to be modulated by complex behavioral mechanisms that do not always maximize the group's benefits. The quantitative understanding of crowd behaviors opens the way for designing bottom-up management strategies bound to promote the emergence of efficient collective behaviors in crowds. © 2012 Moussaïd et al.


Moussaïd, M., Guillot, E., Moreau, M., Fehrenbach, J., Chabiron, O., Lemercier, S., …Theraulaz, G. (2012). Traffic instabilities in self-organized pedestrian crowds. PLoS Computational Biology, 8(3), e1002442.

Journal Article Type Article
Acceptance Date Feb 8, 2012
Publication Date Mar 1, 2012
Journal PLoS Computational Biology
Print ISSN 1553-734X
Electronic ISSN 1553-7358
Publisher Public Library of Science
Peer Reviewed Peer Reviewed
Volume 8
Issue 3
Pages e1002442
Keywords traffic, instabilities, self-organized, pedestrian, crowds
Public URL
Publisher URL


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