The September 29 stampede at Mumbai's Elphinstone Road station, which claimed 22 lives and injured scores, is a stark reminder that high-density crowds can be lethal. While mass gatherings are usually safe, stampedes have known to occur at pilgrimages, music concerts, sporting events, protest rallies and even discount sale days such as Black Friday. Many think that if people just acted rationally they wouldn't be crushed to death.
But research into crowd dynamics shows that it's not panic that kills.
In a populous country such as India, crowds are inevitable but a little awareness of the warning signs of a high-density crowd formation can be the difference between life and death.
In this fact file we bust some of the myths surrounding stampedes, explain the science behind high-density crowds and provide life-saving tips to survive a stampede.
Contrary to myth, it is not injuries from being trampled upon that kills people but asphyxiation that leads to death.
It is also worthy to remember that not all stampedes result in fatalities.
WATCH OUT FOR A HIGH-DENSITY CROWD
A high-density crowd is when there are six or more people per square meter, six being the minimum. In high-density crowds, people are squeezed together so tightly that they can no longer choose where to go and begin to resemble the movement of a fluid. Such crowds can develop pressure waves that can exceed 1,000 pounds of force. These waves can travel through the group causing it to lose control.
High-density crowds can kill in two ways, 1) crowd crush, 2) progressive crowd collapse
A crowd crush is when people are jammed together so tightly that they can no longer inflate their lungs and they gradually die of asphyxiation or suffocation. The people who die in crowd crushes are usually the ones against the wall. Crowd crushes happen when an ever increasing number of people try to fit into a confined space, either trying to get in or get out.
PROGRESSIVE CROWD COLLAPSE
A progressive crowd collapse occurs when one person suddenly falls because of the pressure the crowd is exerting on them or because they slip. Those adjacent are denied the support of the fallen person's body they were leaning against but are still under pressure from the other side. This ultimately results in a domino effect where those adjacent are knocked over.
The result is a hole where more and more people are forced into creating a pile of bodies atop each other until the pressure eases. This is usually seen when a large tightly packed crowd is moving forward steadily through a confined space.
"Crowd forces can reach levels that almost impossible to resist or control. Virtually all crowd deaths are due to compressive asphyxia and not the "trampling" reported by the news media. Evidence of bent steel railings after several fatal crowd incidents show that forces of more than 4500N (1,000lbs) occurred. Forces are due to pushing, and the domino effect of people leaning against each other,"
Keith Still, professor of crowd science at Manchester Metropolitan University said on his website -
A video by HowStuffWorks illustrates how high-density crowds can be lethal.
HOW TO ESCAPE A HIGH-DENSITY CROWD
- Stay on your feet. Your best chance of making it out alive are if you are standing upright. Do not bend to pick up anything you may have dropped or dislodged such as a phone, wallet or a shoe. If your child has stumbled pick them up immediately.
- Keep your hands by your chest, like a boxer. This ensures mobility and creates an air pocket that protects your lungs.
- Stop talking and listen for signs of distress from those at the front of the crowd
- Be aware of the ground you are on, uneven or wet surfaces increase the chances of a progressive crowd collapse
- Do not push against the crowd or try to move in the direction against it. Move sideways. Conserve your energy, do not yell
- Note all the exits, take the path of least resistance, not necessarily the main exit
- Avoid barricades, railings and walls that you can be pinned against
- If you fall and cannot get up, turn to your side protect your head with your hands and draw in your legs. Lying on your stomach or back will leave your lungs exposed