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A street in the Itaewon district is shown crowded with people in Seoul on Saturday night.
Yonhap/Reuters
If you’re in a crowd and people are close enough to bump into you, it might be too crowded.
That’s according to G. Keith Still, visiting professor of crowd science at Suffolk University and head of GKStill International, a consultancy that trains event organizers on how to spot danger.
These events, such as the apparent surge in crowds at packed Halloween parties in the South Korean capital of Seoul and the tragedy at Houston’s Astroworld festival in November 2021, have resulted in multiple deaths and injuries.
Still, who has been studying the dynamics of crowd behavior and safety for more than 30 years, he said organizers can help prevent crowd crush incidents by monitoring a crowd’s density in real time and regulating the flow of people to a place.
The density of people can be calculated as the number of people per square meter, about one square yard. Younger, smaller people take up less space than older, older people, but as a general rule, things get uncomfortable once you get to five people per square meter, Still said, and anything more crowded can become dangerous
“When bodies touch, that high energy and density can result in these crowd surges and collapses,” Still said.
A sign that a crowd has become too dense is what Still called a “wheatfield effect,” where people sway uncontrollably. He said an example can be seen in online videos of a 2005 Oasis concert in Manchester, England, just before a huge crowd surge hit the stage.
The key to preventing a disaster, Still said, is for organizers to monitor density and, if it starts to increase, slow or stop the flow of people into the area. He said it is much more difficult to reduce crowding once the situation has become too dense.
If a spot gets too busy, Still said, performers should stop and ask everyone to step back. Over the years, several performers, including A$AP Rocky and Linkin Park, have done just that.
If you’re in a crowd, Still said you can help stay safe by keeping an eye on areas that may be more crowded and getting out of the crowd if you don’t have enough personal space.
You can learn more by viewing an interactive graphic here.