Four years of recordings of the movements of the crowd during the Chupinazo From the San Fermín festivities, in Pamplona, and the analysis through artificial intelligence, they have served a team of researchers to discover that the more than 5,000 people who meet in the famous place every July 6 behave like a fluid and synchronize and synchronize Your movements.
The work, which is published this Wednesday In the magazine Natureshows that when the density of the crowd reaches a critical threshold of 4 people per square meter, collective behavior changes. At that time there are a series of predictable oscillations every 18 seconds, a finding that could serve in the future to detect changes in patterns and possible danger situations.
“What we find is that there is a kind of global collective movement with a characteristic frequency and time, with small groups that move by oscillations in the script and anti -hydrial sense every 18 seconds,” he explains Iker ZuriguelResearcher at the Granular Media Laboratory at the University of Navarra (UNAV) and co -author of the article. “This means that you can predict more or less when it will change, and this is relevant, because it was said is movements of this type are chaotic, turbulent and unpredictable, and it turns out that it is not true.”
People like sand grains
The French researcher laboratory Denis Bartololed by the study, had already analyzed other “human tides”, such as collective movements In the Chicago Marathon. Applying mathematical models that are used in hydrodynamic, he and his team discovered that runners stop in small groups and generate a pattern similar to that of A Wave Train in the Ocean. Studying the behavior of crowds is a great challenge, essential to improve the safety of great events, in which thousands of people move at the same time in small spaces.
As the density rises in a group, you can no longer move where you want: you become part of the flow
Iker Zuriguel
– Researcher at the University of Navarra (UNAV) and co -author of the article
It was when he had news about the work on the Chicago Marathon when Iker Zuriguel, who has been attending the San Fermín festivities for years, it occurred to him that it could be a good example of study and contacted Bartolo’s team to propose their follow -up . “We have studied people’s behavior In evacuations scenariosanalyzing individuals as if they were grains of sand, ”he explains to eldiario.es. “A person differs from a grain of sand that we can think and move but, as the density rises in a group, you can no longer move where you want: you become part of the flow.”
THE AGLOMERATION THROGY
The works began in 2019 and were interrupted by the pandemic in 2020 and 2021. Being in Navarra, Zuriguel assumed the logistics challenge of getting the balconies from which to place the cameras and have a good perspective of the movement of the crowds. Through their images and a mathematical model, the authors saw that the density of the crowds changed 2 people per square meter in the hour before the start of the festival to 6 people per square meter during the event, until reaching a maximum density of 9 people per square meter.
When this threshold of 4 people per square meter was reached, the authors observed groups of several hundred people who behaved spontaneously “as a fluid that ranged in a predictable interval without external stimuli.” To prove the solidity of their findings, the authors compared their results with the dynamics that occurred in the 2010 Love Parade disaster, a human avalanche at the ‘Tecno’ Music Festival of the German city of Duisburg in which 21 people died. And they found that when the crowd reached a density similar to that of the San Fermín festivities, the same oscillations were observed.
The “Divide” square
An interesting aspect of the study is that scientists have proven that the periods of oscillation of the crowd depend on the amplitude of the space in which they move. “Our proposal is that this period depends on the size of the square,” explains Zuriguel. “The same type of movement appeared in the Love Parade because the site was smaller, but where we could see it more clearly it was in Chupinazo himself.”
When the material examines again, they realized that the moment when a gaiter band escorted by the police and divides the square into two groups, allowed them to test their hypothesis. “The square was departed in two and the oscillation time was reduced in each of the two new groups,” explains the expert. With these new data, the authors believe that we are closer to developing live monitoring systems that allow anticipating the behavior of large crowds in confined spaces and trying to prevent accidents.
“The conclusion is that this type of oscillation appears that so far nobody had found,” Zurigule summarizes. “And maybe we can use this knowledge to prevent accidents or improve evacuations.”
“A titanic achievement”
Iñaki EcheverríaResearcher of the Department of Physics and Applied Mathematics of the University of Navarra who has not participated in the study, considers that characterizing this system represents a titanic achievement. “In my opinion, the most relevant aspect is that the patterns observed in San Fermín are not exclusive to this event,” he says eldiario.es. “The same phenomena have been identified in the tragedy of the Love Parad in mass events ”.
The same phenomena have been identified in the tragedy of the Love Parade in 2010, suggesting that these dynamics emerge naturally and will help in accident prevention
Iñaki Echeverría
– Researcher of the Department of Physics and Applied Mathematics of the UNAV
José Javier RamascoUrban Mobility Expert of the Institute of Interdisciplinary Physics and Complex Systems (IFISC), believes that the study has great value, because it provides a different approach to other works such as monitoring of the masses in MECA, which study the person movement person to person. “There it has been seen that just before accidents there are strange and chaotic movements of the dough, which acts as a block,” he explains. “Luckily, in San Fermín nothing happens because they do not exceed the limit and the environment is festive, but if there is any type of phenomenon that disagree the panic there may be serious problems.”
Know that the appearance of these oscillations depends on the number of people per square meter, he comments Claudio Hernándezpostdoctoral researcher at the Amolf Institute (Amsterdam, the Netherlands), would allow implementing a safety margin to avoid problems. Another interesting point is that oscillations in closed systems depend on the geometry of the edges, he explains in statements to the SMC. “Therefore, the design of spaces that dissipate unwanted oscillations could be studied, thus minimizing the risk of crushing accidents.”
On the security situation in San Fermín, Iker Zuriguel believes that there are some key elements that differentiate it from what happened in the Love Parade (where the dough was heading towards a tunnel) or the agglomerations of the Mecca. “In this case the streets that give access to the square are very large compared to the size of the square,” he says. “And there are many, which I think gives a sense of security, that people can go on one side or another. And then, obviously, the party atmosphere. ” But you have to be vigilant, he concludes, because something that changes the behavior of the crowd of blow can always happen and the disaster occurs.
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