A stampede implies that people had space to run, which was not the case in Itaewon, he added. The more people in the crowd, the greater the force of the crowd crush.
“The whole crowd goes down as one, and if you’re in a confined space, people can’t get up again,” Still said.
How human stampedes, like the one near Mecca, turn deadly
In a Twitter thread on Saturday, a person who said they were in the crowd describe people “fall like dominoes and scream”.
“I really felt like I was crushed to death,” they said in another Tweeter. “And I breathed through a hole and cried and thought I was dying.” The person continued, writing that they were near the top of the crowd, shouting, “Please save me! and people nearby pulled them up.
During a surge, the pressure above and below people in the crowd makes it difficult to breathe as their lungs need room to expand. Still said it took about six minutes to go into compressive or restrictive asphyxiation, the likely cause of death for those killed in a crowd crush.
People can also injure their limbs and lose consciousness as they struggle to breathe and escape crowds. It takes about 30 seconds of compression to restrict blood flow to the brain and for people in a crowd crush to become dizzy.
Crowd surges can be triggered by many difficult situations, such as people pushing others or someone tripping, Still said. But events aren’t usually caused by people in distress or pushing their way out of a crowd. These reactions usually come after the crowd begins to break down, Still said.
“People don’t die because they panicked,” he said. “They are panicking because they are dying. So what happens is when bodies fall, when people fall on top of each other, people have a hard time getting up and you end up with arms and legs twisting together.
Similar events have happened around the world, including this month at a soccer stadium in Indonesia that killed 130 and last year at the Astroworld Festival in Texas that killed 10.
Most of Astroworld’s dead victims were in a heavily populated area, video timeline shows
At Astroworld, most of the deceased fans were close together in the southern quadrant of the room. The venue was surrounded by metal barriers, which would have compressed people if a crowd had arisen nearby, allowing no way to regulate the flow of people.
Although the crash in Itaewon happened on a street, the crowd was so dense that movement was extremely restricted and there was no way for people to get out vertically, said Norman Badler, a professor at the University of Pennsylvania which studied crowd compression.
Over the past year, crowds have gathered more frequently since pandemic restrictions were largely eased, another factor in recent crowd surges. More people are likely attending events such as Halloween celebrations in Itaewon, Still said, because they have been restricted for so long.
He added that the increase in mass gatherings that are now permitted underscores the need for crowd management training, which had diminished when the pandemic hit because large events were rare.
Martyn Amos, a professor at Northumbria University in England who studies crowds, said such large events require proper planning and trained people to handle crowds.
“The general point is that these incidents will continue to occur until we 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. .