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The Print
a day ago
- Science
- The Print
Bengaluru stampede tragedy: What science tells us about crowd control
Several stampedes have occurred in India just this year. On 15 February, a stampede at the New Delhi Railway Station killed 18 people, including many passengers who were travelling to the Maha Kumbh Mela in Prayagraj, which also experienced a stampede in January. At least 30 people died at the religious gathering as crowd management measures failed. Published in Nature in February, the study analysed video footage from Spain's San Fermin festival, popular for its running of the bulls event held in July every year. Researchers found that when crowds reached a certain density, spontaneous and rhythmic patterns emerged. Termed 'collective oscillation', the crowd self-organised, and began forming involuntary large-scale, wave-like patterns. New Delhi : A stampede during Royal Challengers Bengaluru's victory celebrations outside the Chinnaswamy Stadium claimed 11 lives Wednesday, and injured several others. Stampedes are recurring tragedies in India, but a study by French and Spanish researchers suggests that patterns emerge in tightly packed crowds. The correct identification of these oscillations, and monitoring via drones and CCTVs, can ensure crowd control and safety during mass gatherings, it says. While these events haven't undergone any scientific scrutiny, the observations from the study in Nature have the potential to help organisers prevent the next stampede. In an interview to The New York Times, France-based physicist Dr. Denis Bartolo, who co-authored the study, said that he placed cameras across the plaza to film the movements of the crowd below. At first, it seemed 'erratic, chaotic, turbulent'. But Bartolo and his team applied fluid dynamic techniques to 'measure the flow of a material by inspecting its direction and velocity'. Similar orbital motions—which took 18 seconds to complete in that particular plaza—were detected right before a stampede that took place at the 2010 Love Parade in Duisburg, Germany, the study shows. The researchers found that above a critical density of people, these oscillations emerge almost organically, without any external guidance. These oscillations are caused by random interactions between people—a slight nudge to gain space, a shuffling of feet, or even an adjustment of posture. These 'odd frictional forces' provide a sort of collective quality to the crowd, leading the mass to exhibit properties similar to fluids. By mapping where and when oscillations start, organisers of mass events can use monitoring tools, like drones or CCTVs, to identify areas in the crowd before a disaster occurs. If these circular motions are detected, the relevant action can be taken, thereby averting stampede-like situations. A similar study, published in Nature in December 2024, studied how crowds behave in marathon events, where groups of runners move in the same direction. Particularly, the goal was to 'investigate the impact of race staff on crowd dynamics'. Similar to ripples in water, the simulations showed wave-like patterns coursing through the crowd. 'We can very clearly observe that starting from the initial homogeneous and random velocity of particles, density and velocity patterns are formed,' read the report by researchers from Indian Institute of Technology-Banaras Hindu University. But an NYT report warned that real-world applications may be limited—'It's one thing to have a well-lit venue filmed with high-quality cameras. But grainy nighttime security footage, for instance, may not reveal the telltale circular movements.' However, recognising that patterns form right before stampede-like events is the first step to building effective crowd management techniques. (Edited by Mannat Chugh) Also Read: 'My brother was crazy about cricket, it took his life': Chinnaswamy stampede leaves families devastated
Observer
12-02-2025
- Science
- Observer
The physics that keeps a crowd from becoming a stampede
Every July, at the opening ceremony of the San Fermín festival signaling the imminent start of the running of the bulls in Pamplona, Spain, more than 5,000 people cram into the city's central plaza. Participants have described the raucous crush of people to Denis Bartolo, a physicist at the École Normale Supérieure in Lyon, France, who hasn't dared step foot in the plaza himself. 'It's not just that you're feeling uncomfortable,' he said he'd been told. 'It becomes painful like you can feel pressure on your chest.' Over several years, he studied the event hoping to one day help prevent stampedes that can turn lethal in large events. In a paper published in the journal Nature, Bartolo, and his colleagues say it may be possible to predict the spontaneous motion of a large crowd once the density of people crosses a critical threshold. Bartolo's team mounted cameras on the balconies of two buildings and found that the crowds turned out to be less chaotic than they might have otherwise appeared. Within the sea of people, circular oscillations were detected. 'We are talking about hundreds, if not thousands, of people, all following the same circular trajectory in sync,' Bartolo said. In addition, the orbital motions, in which each person traces out a rough circle from their starting point in the crowd, took 18 seconds to complete in this particular plaza. The team then examined surveillance footage of the 2010 Love Parade in Duisburg, Germany, where 21 died in a stampede, and detected the same oscillations emerging just before the stampede. The researchers found that above a certain density, these movements emerge spontaneously. They don't depend on some internal or external force, such as people actively pushing one another. Bartolo suggests monitoring crowds for these motions. Detecting them can offer wa arning of danger ahead. By catching oscillations when they're small, event organizers could ask the crowd to disperse or stand still, before the orbits grow in size and lead to people being crushed or trampled. This article originally appeared in
New York Times
05-02-2025
- Science
- New York Times
The Physics That Keeps a Crowd From Becoming a Stampede
Every July, at the opening ceremony of the San Fermín festival signaling the imminent start of the running of the bulls in Pamplona, Spain, more than 5,000 people cram into the city's central plaza. The crowd starts the morning dressed in white. By noon, much of their clothing has been dyed pink by the free-flowing sangria. Participants in the event have described the raucous crush of people to Denis Bartolo, a physicist at the École Normale Supérieure in Lyon, France, who hasn't dared step foot in the plaza himself. 'The density of people is so high that it's not just that you're feeling uncomfortable,' he said he'd been told. 'It becomes painful, like you can feel pressure on your chest.' Over several years, he filmed and studied the event with the goal of perhaps one day helping prevent stampedes that can turn lethal in large public events. In a paper published Wednesday in the journal Nature, Dr. Bartolo and his colleagues say it may be possible to predict the spontaneous motion of a large crowd in a confined space once the density of people crosses a critical threshold. Studying large, densely packed crowds is notoriously difficult. 'You cannot just invite a thousand people to participate in an experiment,' Dr. Bartolo said. Even if he could, 'I wouldn't know how to guarantee their safety,' he added. That's why the San Fermín festival was so appealing. It involves thousands of people who gather predictably, and relatively calmly, each year. Dr. Bartolo and his colleagues mounted cameras on the upper balconies of two buildings on opposite sides of the plaza to film the attendees amassed below. 'If you take a look at the video, indeed the dynamics seem to be erratic, chaotic, turbulent,' he said. But he wondered whether he could tease out an organizing principle that governed the movements of the crowd. Analyzing the footage presented a challenge akin to studying the flow of water. 'Of course you cannot detect the position of every single molecule of water. It's impossible,' Dr. Bartolo said. And yet there are mathematical techniques from the field of fluid dynamics that allow researchers to measure the flow of a material by inspecting its direction and velocity. Dr. Bartolo applied these same methods to the San Fermín festival. The crowds turned out to be less chaotic than they appeared. Instead, the researchers detected circular oscillations within the sea of people. 'We are talking about hundreds, if not thousands, of people, all following the same circular trajectory in sync,' Dr. Bartolo said. In addition, the orbital motions, in which each person traces out a rough circle from their individual starting point in the crowd, took 18 seconds to complete in this particular plaza. The timing was so reliable that Dr. Bartolo said 'you can set your clock' to the dynamics of this crowd, even if the movements might initially seem random. The research team then applied what they'd learned to a deadly stampede. They examined surveillance footage of the 2010 Love Parade in Duisburg, Germany, where 21 died and hundreds more were injured in a stampede. 'And we detected the very same oscillations,' which emerged just before the deadly stampede, Dr. Bartolo said. When the researchers built a mathematical model of crowd mechanics, they found that above a critical density of people, these circular movements emerge spontaneously. They don't depend on some internal or external force, such as people actively pushing one another. As a safety precaution, Dr. Bartolo suggests monitoring densely packed crowds for these orbital motions. Detecting them can offer advance warning of the emergence of dangerous and uncontrolled movements. By catching oscillations when they're small, he says event organizers could ask the crowd to disperse, or stand still, before the orbits grow in size and lead to people being crushed or trampled. 'We're not quite there yet,' Annalisa Quaini, a computational mathematician at the University of Houston who wasn't involved in the study, said of such real-world applications. It's one thing to have a well-lit venue filmed with high-quality cameras. But grainy nighttime security footage, for instance, may not reveal the telltale circular movements. Still, Dr. Quaini called the research an important contribution to understanding the collective behavior of large dense crowds. 'This is a huge effort,' she said. 'And one day, we will be able to use it in a practical setting.'
