Warning signs that a crowd is dangerously dense

 If you’re in a crowd and people are close enough to bump against you, it could be getting too crowded.

That’s according to G. Keith Still, a visiting professor of crowd science at the University of Suffolk and head of GKStill International, a consultancy that trains event organizers on how to spot danger.

Such events, like the apparent crowd surge at packed Halloween festivities in the South Korean capital of Seoul and the tragedy at Houston’s Astroworld Festival in November 2021, have led to multiple deaths and injuries.

Still, who has been studying the dynamics of crowd behavior and safety for over 30 years, said organizers can help prevent crowd-crushing incidents by monitoring a crowd’s density in real-time and regulating the flow of people into a venue.

Crowd density can be calculated in number of people per square meter, roughly a square yard. Younger, smaller people occupy less space than older and larger people, but as a rule things get uncomfortable once you reach five people per square meter, Still said — and anything more crowded can become dangerous.

1 person / m²

Here’s what one person per square meter looks like from above, as depicted in a simulation projected on two tennis courts. (Each square on the grid is 25 square meters, or about the area of six king-size beds.)

2 people / m²

Here are the same tennis courts with two people per square meter.

3 people / m²

At three people per square meter, it’s busy, but not packed, and everyone has some space around them. Still said this level of density is typical for an evening at a bar or pub, especially before the Covid-19 pandemic.

4 people / m²

At four people per square meter, everyone is a bit closer together but still not in each others’ personal space. Still said it’s similar to the distance people keep while in line in the United Kingdom or the United States.

5 people / m²

With a density of five people per square meter, there’s more physical contact between people. This could still be safe in calm spectator situations but can start to become a problem if there’s pushing or shoving.

6 people / m²

At six people per square meter, the situation can start to get dangerous. There’s more physical contact and it’s harder for each person to keep a wider stance, making it much easier for people to tip over. At this point, those in the crowd can easily lose the ability to control their own movement.

“When bodies are touching, that high energy and density can give rise to these surges and crowd collapses,” Still said.

One sign a crowd has become too dense is what Still called a “field of wheat effect,” where people are uncontrollably swaying. He said an example is visible in online videos of a 2005 Oasis concert in Manchester, England, just before a big surge rippled through the crowd toward the stage.

Keeping people safe means being able to spot when a crowd is becoming too dense, but that’s trickier than it sounds. Among other things, he said, it depends on the angle of view, say from a helicopter or stage.

Can you tell which of these simulated gatherings is the most crowded?

It’s a trick question: They all show the same density — four people per square meter — from different angles.

Compare the last image to this one, which shows a more dangerous density of six people per square meter.

While these last two images look very similar, the “tell,” Still said, is the gap between people.

In his crowd-safety classes, Still encourages event organizers to post versions of these images on the wall of the command center, or even a DJ table, and repeatedly compare the reference images of varying densities with what they see before them or on television monitors, he said.

The key to preventing a disaster, Still said, is for organizers to watch the density and, if it starts to get high, slow or stop the flow of people entering the area. He said it’s much harder to reduce crowding once the situation has become too dense.

If a venue does get too crowded, Still said, performers should stop and ask everyone to take a step back. Over the years, several performers, including A$AP Rocky and Linkin Park, have done exactly that.

Following crowd-related disasters such as a crush at the Hillsborough soccer stadium in 1989, a fire at the Station nightclub in 2003 and a stampede at the E2 nightclub the same year, many jurisdictions adopted crowd-related regulations and required licensed “crowd managers” to be on site to enforce safety rules.

A 56-page operations plan for the Astroworld event, obtained by CNN, includes a section about “incident management” that reads, “The Festival employs experienced, licensed event security to assist with crowd management and security at the scene of an incident.” Another section says, “Crowd management techniques will be employed to identify potentially dangerous crowd behavior in its early stages in an effort to prevent a civil disturbance/riot.”

If you’re in a crowd, Still said you can help yourself stay safe by watching out for areas likely to become most crowded, and making your way out of the crowd if you don’t have enough personal space.

Amy Cox, who produces festivals and events as senior vice president at Deep South Entertainment, said she has a simple rule of thumb in an event crowd. “Personally, for me it’s: Can I put my hands on my hips comfortably without touching anyone else?”

https://edition.cnn.com/interactive/2021/11/us/crowd-density-dangerous-warning-signs/