June 2022. The Hellfest festival is in full swing in the town of Clisson, in Loire-Atlantique. On average, 65,000 spectators come every day to marvel at the rhythm of metal music. But, this year the event has some unusual visitors. At the heart of the public, two researchers from the National Institute for Research in Digital Science and Technology (Inria) dance for science. They are distinguished by their orange caps and their suits full of sensors. Written on their back: “Hellfest & Inria are collaborating here to study crowds. »
Sensor data combined with images taken by a camera from the stage allow them to observe how the audience moves. “At Hellfest, the dances are quite physical. We seek to understand how people are in contact and how these contacts become movements that spread through the crowd., summarizes Julien Pettre, researcher at Inria Rennes. The institute is conducting this study as part of the CrowdDNA project, launched in 2020 by the European Union. The initiative brings together specialists in biomechanics, physics, cognitive science and computer science from several European countries. Their goal: to prevent accidents in large gatherings.
“Crowd management is usually a manual processlaments Julien Pettre. Staff on site have a very partial view of the crowd. Several examples show that this mistaken perception can lead to disasters. » Some have claimed tens of thousands of lives in musical, religious and sporting events over the past decades. Victims ran out of oxygen after being overcrowded. Others lost their footing and were trampled on.
The stampede during a rally in Mecca in 2015 claimed the lives of some 2,300 people. Most recently, on November 5, 2021, ten people died and more than 300 were injured when concertgoers crowded the front of the stage at a concert by rapper Travis Scott in Texas.
For the seven CrowdDNA project teams, spread across four European countries, understanding such phenomena begins in the laboratory. At the research center in Juliers, Germany, three people equipped with sensors are placed in line on a mattress. An impulse is given to the individual at the back and propagates forward. Then, the experiment is repeated with five, ten, thirty and fifty people. Human pendulums, like these aligned marbles which transmit their energy to their neighbors, in a way. Except that here the muscles of the bodies bring additional energy to the system. The researchers thus observe how a moderate flare-up can take on a large scale.
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