Crowd dynamics and auditorium management
This article originally appeared in Auditorium News published by the International Association of Auditorium Managers in May 1984.By John J. Fruin
Among the many skills required of auditorium managers is an understanding of crowd dynamics and the relationship of crowding to facility design and management. Concentrations of large groups of people occur normally in a variety of different places. For example, 50,000 employees and 80,000 visitors move through the New York World Trade Centre each day, and the complex uses 260 elevators and 53 escalators for vertical transportation within its two 110-story office towers and the other buildings surrounding its broad plaza. Many large transportation terminals serve more than 100,000 passengers daily. Crowds of this size are also not unusual at outdoor stadiums. The quality of the human experience in each of these environments is largely determined by the interaction of the building's architectural design and efficient crowd management. Perhaps even more important, these factors also determine the safety of the public.
Numerous incidents have been recorded in which uncontrolled crowding has resulted in injuries and, in some instances, death. The 1979 "Who" concert disaster in Cincinnati, in which 11 persons were killed, dramatically emphasized the lethal potential of uncontrolled crowds. These deaths occurred when 18,000 eager rock fans rushed the entrance of the Cincinnati Coliseum. Other similar incidents show that such disasters can happen in any type of group or environment. Seven persons were killed in Forteleza, Brazil, and another seven in Kinshasa, Zaire, by crowd rushes during Pope John Paul II's 1980 tour. There is a long list of crowd fatalities at international soccer stadiums, including a 1970 incident in Glasgow, Scotland, that resulted in 66 deaths and 200 injuries.
Fortunately, major crowd disasters like these are rare, but crowd-related falls and other accidents associated with crowding are relatively common. Frequently, these accidents result in liability claims, based on allegations of negligence in facility design or management. Most of these accidents are found to be caused by personal carelessness, but a few reveal lack of understanding of the dynamics of crowds.
A systems analysis "model" is presented in this article to help explain these dynamics. I first used this model as a consultant to the task force investigating the Cincinnati Coliseum disaster. The model provides a simple basis for understanding crowding and its relationship to facility management and the design of places of public assembly.
The dynamics of crowds
Fundamentally, there are four interacting elements in every crowd situation: time, space, information, and energy.
The time is simply the period during which the crowding occurs; space, the size and configuration of the area occupied; information, the perceptions by those in the crowd, real or imagined, that cause it to take some group action; and energy, the pressures created by massed pedestrians that can result in accidents and death.
Analysis of more than a dozen serious crowd incidents has shown that in all cases these elements have played a critical role, and that management strategies based on one or more of these elements could have averted or significantly reduced crowd effects.
Auditorium managers are familiar with the influence of time on crowding. All have observed the differences in traffic characteristics between the gradual arrival of patrons before a performance as compared to the mass exodus that occurs immediately after. Because of the shorter time span at the end of the performance, pedestrian facilities are taxed to the maximum, and dense crowding often occurs. The exceptions to this pattern are "early arrival" events, where a large accumulation of patrons may build up prior to gate opening.
A review of crowd disasters shows that typically- they occur in short periods of time when the critical capacity of a facility has been temporarily exceeded but intensive pressure to use the facility continues. Usually, the crowd continues to press ahead because it has no knowledge of what conditions are at the bottleneck. Those at the bottleneck find it impossible to resist the crowd pressures from behind.
This element is considered in two ways when analyzing crowd effects. The first is the critical density or average area per person that occurs in uncontrolled crowds, and the other is the particular architectural configuration or type of pedestrian facility involved. When average densities in a crowd reach the approximate area of the human body, -about one-and one-half square feet per person, individual control of movement becomes impossible, and phenomena such as shock waves will be propagated through the crowd mass and cause the sudden uncontrolled surges that unleash the crowd's destructive force.
Architectural features that typically are implicated in dangerous crowding incidents are those that rigidly confine people within an inadequate space, or are not properly designed for crowd pressures and efficient mass movement. This includes corridors and stairs of inadequate width, insufficient numbers of doors or gates, escalators, and protective guardrails that are either too low or not provided at all. Minor design deficiencies that present no apparent problems under normal traffic conditions can be accentuated in crowds, potentially triggering more dangerous, "domino effect" accidents. This effect is best illustrated by a moving walkway accident at the
1970 Japanese Exposition, in which 42 persons were injured in a pileup when one fell at the system exit. In thiscase the mechanical delivery characteristic of the moving walk caused the pileup, but most crowd incidents exhibit the same sort of continuous pressure.
The perceptions of people in a crowd determine whether the crowd crush will be just an unpleasant experience, or end in disaster. People in a crowd do not have a broad view of what is happening around them, and unless authoritative information is received from a reliable source, will act on the speculations of others nearby. If there is a perception of danger, the human flight response can cause the sudden type of movement that unleashes the massed energy of the crowd. The opposite of the flight response can also occur-a "craze," or competitive scramble to attain some intensely desired or valued objective. The Cincinnati Coliseum and Pope's tour incidents are examples of the type of rush where no threat exists.
In systems analysis, information is also viewed in other ways. For example, tickets that require patrons to use different entrances are an information element that reduces crowding by spreading patrons out over a larger and more separated area. Another example is the time-of-arrival ticket, like those used in the King Tut exhibit tour, which regulates patron arrivals by spreading them over a longer time period. The reserved seat ticket as compared to general admission can be considered an information element, because it reduces the urgency connected with attempts to obtain a better seat.
The phenomenal forces that are produced by a crowd mass once it reaches critical density are almost impossible to stop. Reports of persons being literally lifted out of their shoes and of clothes being torn off are common in uncontrolled crowd situations. Survivors of crowd disasters report difficulty in breathing because of crowd pressures, and asphyxia, very likely accentuated by fear, is a more common cause of crowd deaths than trampling.
As some indication of the forces involved, the failure of a steel railing under crowd pressures was noted in the Glasgow, Scotland, soccer stadium disaster. A bent steel railing was also observed at Cincinnati. The force required to bend a 2-inch diameter steel railing 30 inches above the base is estimated at 1,000 pounds.
Auditorium managers can use the systems model elements of time, space, and information to develop control strategies to prevent the occurrence of critical crowd forces. The objective of time based control strategies is to prevent the buildup of large accumulations of patrons in short periods of time. This requires that physical facilities and staffing be adequate to accommodate expected patron flow rates. When possible, the arrival rate of patrons should be managed to prevent crowd accumulations that exceed gate processing capacity.
This is a strategy sometimes used to control the rate of arrivals and degree of crowding at a known pedestrian bottleneck. This technique is used in Madison Square Garden at the end of a performance to limit the number of patrons entering escalator landings. Garden attendants regulate the flow into these landings to maintain safe occupancy levels. The attendants can also quickly shut down escalators if necessary.This technique can be used at stairs, near open balconies, doors, or entrance gates, where uncontrolled crowding might cause problems. The pedestrian bridge connecting the Oakland Stadium with the BART subway system in San Francisco has been designed as a meter, with the pedestrian traffic capacity of the bridge limited to the passenger capacity of the subway. Metering must be applied with caution, since it also produces an accumulation of waiting pedestrians. Properly planning metering keeps waiting lines away from the bottleneck in areas where better control is possible.
Managers should develop a good sense of the patron capacities and processing rates of all the pedestrian facilities and spaces for which they are responsible. Short counts, using a stopwatch and hand counter, can be made of ticket takers, stairs, doors, escalators, checkrooms, and so on, to develop this "feel." Processing rates will vary according to the type of event and the patrons. The crowd at a hockey game will naturally be much different from the one at a children’s' circus. Differences in the traffic characteristics of pedestrian facilities should be carefully noted. Stairs have less capacity than corridors or ramps, and backups will develop where the two intersect. A stair that has the same overall width as an escalator has about the same pedestrian traffic capacity, but the escalator has the more dangerous mechanical delivery characteristic. For this reason, the entrance and exit approaches of escalators must be kept free of obstructions or conflicts with other traffic flows.
In waiting areas, 20 square feet per patron will allow relatively free movement; 10 square feet, movement on an "excuse me" basis; and 5 square feet, standing without touching others-but with little ability to move freely. This is about the occupancy level that you see in most normal waiting situations, such as approaches to a busy escalator or stair. At approximately 3 square feet per person, involuntary touching and brushing against others will occur, a psychological threshold that should generally be avoided in most public situations. Below 2 square feet per person, potentially dangerous crowd forces and psychological stresses may begin to develop.
To prevent crowding and facilitate pedestrian movement, places of public assembly should provide several dispersed entrances and exits rather than centralized ones. Well-designed auditoriums characteristically have direct lines of patron flow and clear lines of sight. Circuitous and narrow passageways, "dogleg" routes, obscured doorways and stairs, and ambiguous pathways create confusion, and in an emergency flight response situation, have the potential for disaster. In such emergencies "the-line-of-sight" becomes "the-line of flight."
Information strategies to modify the time, space, and energy elements of the crowd model not only involve the use of all types of media, but also the development of a well-planned communication network involving the manager, staff, patrons, and local police and emergency services. A clear chain of responsibility for crowd control and emergency procedures must be established and repeatedly reinforced. This requires formal designation of the authority to open and close pedestrian facilities, make crowd-control-related public address announcements, and summon emergency services. Liaison must be developed and actively maintained with local police, fire, and medical services, and respective roles clearly defined in writing, or, more effectively, in the form of an organization chart. Special events that increase patron attendance beyond the normal require a careful review of the crowd management plan and the adequacy of auditorium facilities and staffing.
The availability and reliability of communications equipment and the means of its use are crowd management considerations. The public address system must be connected to the emergency lighting circuit or other standby power to ensure that communication with patrons is possible during a power failure. A power failure was the cause of a crowd disaster that took many lives in a public building in India. Where two-way radios are used by staff, the compatibility with local emergency service communications equipment should be verified.
Immediate communication with patrons is a good way of quickly defusing a potentially dangerous crowd situation, but the form and wording of the message must be chosen carefully. A misunderstood message, or one that produces a sense of urgency or threat to personal safety, can worsen the situation. Recommended communication techniques and typical messages to be used in handling emergency situations should be included in the crowd management plan and covered in staff training sessions.
Good crowd planning and management improves the public's enjoyment of events and encourages attendance. It also reduces crowd-related accidents, their associated liability claims, and the possibilities of more serious and costly incidents. This is a management skill that is critical both to the patron and the manager.
John J. Fruin, PhD, is a specialist in pedestrian traffic analysis and building circulation system design. He has been a consultant on the design and analysis of circulation elements in transportation terminals, high-rise buildings, and entertainment facilities, and in event planning.
Fruin, John J. “Crowd dynamics and auditorium management.” Auditorium News. May 1984.