Yesterday (April 7th 2010), Science Now (the news section of Science Magazine) published an article by Dave Mosher on our work on pedestrian crowds. The article summarizes the paper we published the same day in PLoS ONE. Hereafter are an excerpt of the Science Article and the abstract of our PLoS ONE paper:
Secret of Annoying Crowds Revealed – From Science Now
Push, shout, or politely excuse yourself all you want, but those slowpokes in your way just won't budge. A new study shows a long-neglected reason why: Up to 70% of people in crowds socially glue themselves into groups of two or more, slowing down traffic. What's worse, as crowds gets denser, groups bend into anti-aerodynamic shapes that exacerbate the problem. The study may be a boon to urban planners.
Human crowd motion is mainly driven by self-organized processes based on local interactions among pedestrians. While most studies of crowd behaviour consider only interactions among isolated individuals, it turns out that up to 70% of people in a crowd are actually moving in groups, such as friends, couples, or families walking together. These groups constitute medium-scale aggregated structures and their impact on crowd dynamics is still largely unknown. In this work, we analyze the motion of approximately 1500 pedestrian groups under natural condition, and show that social interactions among group members generate typical group walking patterns that influence crowd dynamics. At low density, group members tend to walk side by side, forming a line perpendicular to the walking direction. As the density increases, however, the linear walking formation is bent forward, turning it into a V-like pattern. These spatial patterns can be well described by a model based on social communication between group members. We show that the V-like walking pattern facilitates social interactions within the group, but reduces the flow because of its “non-aerodynamic” shape. Therefore, when crowd density increases, the group organization results from a trade-off between walking faster and facilitating social exchange. These insights demonstrate that crowd dynamics is not only determined by physical constraints induced by other pedestrians and the environment, but also significantly by communicative, social interactions among individuals.