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Bullet Stampede
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Causes for Stampedes

Causes of stampedes can be better understood through the FIST MODEL, which describes the primary elements involved in crowd disasters. In other words, the elements provide a model for understanding the causes of crowd disasters, means of prevention, and possible mitigation of an ongoing crowd incident. The elements of the model form the acronym "FIST", which is a useful reminder that any crowd situation can quickly become threatening and potentially lethal. The acronym is defined as follows: FORCE (F) of the crowd, or crowd pressure; INFORMATION (I) upon which the crowd acts or reacts, real or perceived, true or false; SPACE (S) involved in the crowd incident, standing area, physical facilities - stairs, corridors, escalators; TIME (T) duration of incident, event scheduling, facility processing rates

Force

It does not take many people to produce deadly force. If you ve been in such situation, you can t keep your feet on the ground and cannot control where you move. You can just try to keep your balance. 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 extent of forces. Forces are due to pushing, and the domino effect of people leaning against each other.

Compressive asphyxia has occurred from people being stacked up vertically, one on top of the other, or horizontal pushing and leaning forces. In the Ibrox Park soccer stadium incident, police reported that the pile of bodies was 3 m (10 feet) high. At this height, people on the bottom would experience chest pressures assuming half the weight of those above was concentrated in the upper body area.

Horizontal forces sufficient to cause compressive asphyxia would be more dynamic as people push off against each other to obtain breathing space. In the Cincinnati rock concert incident, a line of bodies was found approximately 9 m (30 ft) from a wall near the entrance. This indicates that crowd pressures probably came from both directions as rear ranks pressed forward and front ranks pushed off the wall.

Information

In the broad systems sense, information has many forms. It includes all means of communication, the sights and sounds affecting group perceptions, public address announcements, training and actions of personnel, signs, and even ticketing, which can instigate rapid group movement.

Space

The configuration, capacity, and traffic processing capabilities of assembly facilities determine degrees of crowding. Space includes standing and seating areas, projected occupancies, and the practical working capacities of corridors, ramps, stairs, doors, escalators, and elevators.

Time

A simple illustration of timing is the more gradual and lighter density arrival process before an event, compared to the rapid egress and heavy crowd densities after an event. However, it is found out that the longer the gap between two similar events, the larger the size and density of crowd force it would be.

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