CROWD CRUSH INCIDENTS
The fire inspector, normally concerned with fire safety in places of public assembly, often becomes involved in issues of crowd management. It is important, therefore, to understand crowd crush incidents.
According to the Encyclopedia of Architecture (Volume 3, John Wiley and Sons, 1989), crowd incidents are characterized by the following:
- Rapid accumulation of queuing people (people lining up) as the demand for a facility outstrips its supply or capacity.
- Pedestrian densities approaching 0.67 square feet per person,
- leaving no space between people. Shock waves, causing individuals to move involuntarily as much as 10 feet laterally, can be seen moving through the crowd.
- Competitive rushing by a crowd away from something, termed “panic,” or a competitive rush toward some objective, termed a “craze.”
As far as why crowd incidents occur, four factors have been identified: time, space, energy, and information.
Time. Crowd crushes occur in short intervals of time when the capacity of the facility has been exceeded yet pressure to use the facility continues.
Space. This has a critical impact on the ability of individuals to control their own movement. When densities are reduced below 1.5 square feet per person, individual control of movement becomes impossible. (This is why “festival seating” in open areas with no seats is so dangerous: The control of crowds of people is nearly impossible.) The architectural layout of facilities—including exit widths, confluence or crossing of circulation routes, dispersal/assembly areas around exit/entrance doors, and so on—is an important consideration when analyzing facilities. (Architectural features are an important influence, as was seen in the City College crush incident in New York City in December 1991.)
Energy. Crowds create unbelievable forces. In one case, it was estimated that steel pipe railings were bent by crowds exerting a force of 1,100 lbs. on the rails.
Information. “Front-to-back” communication often is nonexistent in a crowd; individuals being crushed in the middle of a crowd or those being crushed against a barrier (such as a railing) at the front of a crowd are unable to tell others of their plight.
Control of some or all of these factors can mitigate a crowd crush. This could include “metering” people into an event, providing wide dispersal areas around entrances and exits, omitting queue rails for snack stands in the means of egress, or possibly providing video and public address equipment for facility operators to guide crowd movement.
