(CNN) — If you’re in a crowd and people are close enough to bump into you, there may be too many people.
That’s according to Mr Keith Still, visiting professor of mass science at the University of Suffolk and director of GKSkill International, a consultancy that trains event organizers on hazard detection.
Still has been studying the dynamics of crowd behavior and safety for 32 years. Still said organizers can help prevent crowd incidents by monitoring crowd density in real-time conditions and regulating the flow of people to the venue.
Crowd density can be calculated in the number of people per square meter. Younger, smaller people take up less space than older, bigger people, but as a general rule, things get uncomfortable when you hit five people per square foot, Still said, and anything with more people can become dangerous.
“When bodies touch, that high energy and density can cause these human avalanches and collapses,” Still said.
One sign that a crowd has become too thick is what Still calls the “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 large stampede of people stormed the stage.
Protecting people means being able to detect when a crowd is getting too thick, but that’s harder than it sounds. Among other things, he said, it depends on the viewing angle, say from a helicopter or a stage.
The key to preventing disaster, Still said, is for organizers to watch the density and, if it starts to increase, slow or stop the flow of people entering the area. He said it’s much harder to reduce overcrowding once it gets too crowded.
If the venue gets too tight, Still said, performers should stop and ask everyone to step back. Over the years, various artists, including A$AP Rocky and Linkin Park, have done just that.
Following crowd-related disasters such as the Hillsborough collapse in 1989, the Station nightclub fire in 2003, and the E2 nightclub stampede the same year, many jurisdictions adopted crowd-related regulations and required licensed on-site “crowd managers” and enforces security rules.
The 56-page operations plan for the Astroworld event, obtained by CNN, includes a section on “incident management” that reads: “The festival employs experienced and licensed event security personnel to assist with crowd management and venue security.” the place of the incident. The second section reads: “Crowd management techniques will be used to identify potentially dangerous crowd behavior at an early stage in an effort to prevent riots or civil unrest.”
If you’re in a crowd, Still said you can protect yourself by keeping an eye out for areas that are likely to be more crowded and pushing your way through the crowd if you don’t have enough personal space.
Amy Hoy, who produces festivals and events as senior vice president of Deep South Entertainment, said she has a simple rule for big events. “Personally, for me it’s: Can I comfortably put my hands on my hips without touching anyone?”