07-02-2025
Crowds can suddenly turn deadly. New research has clues that could prevent disaster.
Crowds can suddenly turn deadly. New research has clues that could prevent disaster.
Watching a concert or a sports event alongside thousands of other people can be both exhilarating and dangerous, and researchers now have new theories about how people behave when they get too close together.
Crowd crushes have proven to be deadly in recent years. At the 2021 Astroworld festival in Texas, 10 people were crushed to death. In 2010, nearly two dozen were killed as a crowd stampeded at the Love Parade, a techno-music festival in Duisburg, Germany. More than 150 died during a 2022 Halloween crowd surge in Seoul's nightlife district. And hundreds were killed outside Mecca in a stampede during the annual hajj pilgrimage in 2015.
In a new study, researchers analyzed the movement of thousands of spectators attending the San Fermín festival that precedes the start of the Running of the Bulls each year in Pamplona, Spain. Starting in 2019, the team set up cameras each year at the festival, which draws more than 5,000 participants dressed in white to the Plaza Consistorial where people drink and dance until the crowd is too packed for them to move, according to the paper published Wednesday in the journal Nature.
Typically, according to study author François Gu, researchers studying crowd movements try to track each individual to build their models but his team studied the crowd as one free flowing unit, like a gel.
Using this method, Gu and his colleagues determined that every 18 seconds, sections of the crowd about 500 people strong unwittingly found themselves traveling in the same direction and making a circle. To determine if this phenomena repeated itself in more dire situations, the team then analyzed video of a crowd at the 2010 Love Parade,. Researchers found similar dynamics occurred before the stampede.
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These circular motions are likely the result of people moving sideways to avoid being pushed by the tens or hundreds of people around them, said Gu, a physicist at the École Normale Supérieure in Lyon, France.
"So at some point, the whole crowd is gonna turn into on the right, on the left, and this creates this kind of oscillations," he said.
Researchers only observed this phenomena in highly dense, confined crowds and how long the oscillations took depended on how long people were confined, said Gu.
But once a crowd reaches a critical density, people spontaneously get very active which can be "very dangerous," Gu said. This increases the amplitude of the orbital motions ‒ meaning how fast and far people are walking in circles.
Gu said its possible to detect this uptick up to 20 minutes before it occurs. Though it is hard to pick up on these movements from inside the crowd itself, he said outside observers could replicate his methodology during an event. "So our work can act as a detector of catastrophes," he said.
But what's dangerous isn't the crowd itself, he said, its their uncontrolled motion. Even with what he's learned about crowd dynamics and the potential for disaster, Gu still recommended visiting the San Fermín festival.
"A crowd can be dense, but can be also safe," he said.
