Stampede: how it happens

Even a happy, peaceful crowd can suddenly transform into a deadly weapon. In the latest in a long history of stampede or "human crush" tragedies, a woman has died in an out-of-control crowd at the University of Johannesburg. Why does this happen and how can you protect yourself?

Cattle and horses can get spooked and start to stampede, and, despite our considerably more developed brains, so can humans. A mass of people in an enclosed space can become a dangerous creature, prone to deadly self-harm.

If something occurs to frighten a crowd, like a building fire, people make a rush towards exits and away from the perceived threat. Panicked movement is dangerous under any circumstances; in an enclosed space it can prove lethal.

Sometimes simply the sheer force of numbers – too many bodies in a confined space, even if they are moving quite slowly and not panicking – can be enough to crush people to death. It doesn’t have to be a huge or angry crowd either.

The irony is that such tragedies can happen where people gather together in large groups to celebrate: sporting events, religious festivals, music concerts. And often the crush occurs not because people are trying to get away from a perceived threat, but because they are all trying to get towards something desirable, such as inside a stadium to watch their team play, or to listen to their favourite band.

In the latest tragedy, a student's mother was crushed in a crowd all anxious to get registered in time to start the new academic year at the University of Johannesburg. Other people were also injured in the incident.

A sport infamous for crowd disasters 
The history of soccer, more than any other sport, is especially marred by this unnecessary type of disaster.

The most notorious such soccer-related tragedy was at the Hillsborough Stadium in Sheffield, England, in 1989, when 96 people were killed.

Most United Kingdom soccer stadia at the time placed high steel fencing between the spectators and the field, to help protect against hooliganism. At Hillsborough, opposing fans were segregated in separate "pens". An unexpectedly large number of fans trying to enter the stadium caused police to open gates to relieve crowd pressures. Instead, fans surged into the enclosed terraces, crushing people against the railings at the front.

South Africa’s worst sporting disaster happened in 2001 at the Ellis Park Stadium, when poorly controlled crowds surged into the already packed stadium to see Kaizer Chiefs play Orlando Pirates; the ensuing crush left 43 dead. Previously in 1991, 42 people had died in a very similar incident when too many fans were admitted to the Oppenheimer Stadium in Orkney, where the same two teams were playing.

The killer in the crowd
The common conception is that people get trampled to death in human stampedes. People do get hurt and sometimes killed by being trampled underfoot or by being pushed against hard or sharp objects, but the main cause of death in human stampedes is compressive asphyxia, when the chest is compressed or crushed by external forces so that it can’t expand and the person can’t breathe in enough oxygen.

In crowd disasters, this results from people in a confined space pushing and leaning against each other, as well as people then being pushed over and getting stacked one on top of the other, forming a human pile. These horizontal and vertical forces can be equivalent to applying hundreds of kilograms onto the human body; in some disasters, crowd crush forces are powerful enough to bend steel railings.

Even before asphyxia occurs, anxiety and heat from the surrounding press of bodies can make breathing difficult and cause some people to feel weak and pass out.

At densities of about seven people per square meter, says crowd control expert John Fruin, the crowd “becomes almost a fluid mass”. Shock waves can be propagated through the mass sufficient to lift you off of your feet and carry you distances of over three metres.

Don’t get caught in the crush

  • All events involving large numbers need good, pre-emptive crowd control. There should be ample visual evidence of thorough management: personnel such as crowd marshalls and police officers, as well as use of aids such as barriers, signposting and loudspeakers. If such measures aren't clearly apparent, then you don’t want to be in that crowd and you should seriously consider turning right round and going home.
  • Be aware of your surroundings. When you enter a venue make a mental note of where all the exits are. In an emergency, people often try to go out the same way they came in, ignoring alternative, lower-traffic exits.
  • A crowd where people are packed close enough to be touching you on all four sides (i.e. a density of more than four people per square meter), is potentially dangerous and you should calmly try to move out of the area or to the periphery. If you feel pressure coming from one side of the crowd, move in the opposite direction as best you can; don’t push back. There are swells and lulls in a crowd push. Use the lulls to move to open spaces. Inch  your way sideways and backwards from the direction of the crowd push. 

-  Olivia Rose-Innes, EnviroHealth Editor, Health24, updated January 2012

References:
Fruin, J. 1993. The Causes and Prevention of Crowd Disasters. Elsevier Science Publishers B.B.

Read more:
Quizz: Would you survive disaster? 
Fighting panic and phobia

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