A stampede means people had room to run, which was not the case in Itaewon, he said. The more people in the crowd, the greater the strength of the crowd agglomeration.
“The whole crowd goes down as one, and if you’re in a confined space, people can’t get back up,” Still said.
In a Twitter thread on Saturday, one person who said he was in the crowd described people “falling like dominoes and screaming”.
“I really felt like I was going to be crushed to death,” they said in another cheep. “And I breathed through a hole and I cried and I thought I was dying.” The person continued, writing that he was near the top of the crowd, yelling, “Please save me!” and the nearby people stopped them.
During a surge, the pressure from up and down from people in the crowd makes it hard to breathe because your lungs need room to expand. It takes about six minutes to go into compressive or restrictive asphyxiation, the likely cause of death for people who die in crowds, Still said.
People can also injure limbs and lose consciousness as they struggle to breathe and escape the crowd. It takes about 30 seconds of compression to restrict blood flow to the brain and to make people in a crowd dizzy.
Crowd surges can be triggered by many sticky situations, such as when people push each other or someone trips, Still said. But the events are not usually caused by people in distress or pressing their way out of a crowd. Those reactions usually occur after the crowd begins to collapse, Still said.
“People don’t die because they panicked,” he said. “They panic because they are dying. So what happens is, when bodies fall, when people fall on top of each other, people struggle to get up and you end up with twisted arms and legs.”
Similar events have occurred around the world, including this month in a football stadium in indonesiathat left 130 dead, and last year in the astro world festival in Texas, which left 10 dead.
In Astroworld, most of the fans who died were close to each other in the southern quadrant of the place. The place had metal barriers surrounding it, which would have compressed people if a crowd had approached them, not allowing any way to regulate the flow of people.
Although the crowding in Itaewon occurred on one street, the crowd was so dense that movement was extremely restricted and there was no way for people to exit vertically, said Norman Badler, a University of Pennsylvania professor who has researched crowd compression.
Over the past year, crowds have gathered more frequently since pandemic restrictions were widely relaxed, another factor in recent crowd increases. More people are likely to attend events like Itaewon’s Halloween celebrations, Still said, because they’ve been restricted for so long.
He added that the increase in mass gatherings that are now allowed underscores the need for crowd management training, which diminished when the pandemic hit because large events were rare.
Martyn Amos, a professor at Northumbria University in England who studies crowds, said such big events need proper planning and people trained to handle crowds.
“The overall point is that these incidents will continue to occur as long as we don’t put in place proper crowd management processes that anticipate, detect and prevent dangerously high crowd densities,” Amos said in a statement to The Washington Post.
