02 Jul The science of crowds

Andrew Long considers what is mean by crowd management and risk analysis and how design, information and management shape safety.

To safeguard large-scale events, security professionals must understand a fundamental truth: a crowd is not merely a collection of individuals; it is a dynamic, living organism. Historically, early crowd science suggested that crowds were inherently volatile, irrational and prone to instinctive violence. Modern social psychology, however, challenges this outdated notion. Several social psychologists, namely Professor John Drury and Professor Stephen Reicher, argue that crowd behaviour is typically driven by a shared social identity. Far from being inherently destructive, an emergency or shared experience often creates a powerful sense of unity, commonality and togetherness among attendees.

When crowd disasters occur, they are rarely the result of “mob madness”. Instead, they are almost always failures of system design, poor spatial planning and an insufficient understanding of how people move. Understanding crowd psychology enables the suitable management of crowds. Mastering the environment requires drawing a firm line between two critical concepts: crowd management and crowd control.

Proactive management vs. reactive control

• Crowd management (proactive): This is the systematic planning for, and supervision of, the orderly movement and assembly of people. It involves evaluating space capabilities prior to use — assessing projected occupancy levels, the adequacy of ingress and egress routes, ticketing processing times and expected group behaviours. It is the formal process of facilitating movement and enjoyment.
• Crowd control (reactive): Conversely, crowd control encompasses the measures taken once a crowd begins to, or has already, got out of hand. It is implemented when a crowd starts engaging in unwanted or dangerous behaviours.

The Golden Rule: Crowd management is proactive; crowd control is reactive. A robust proactive strategy drastically minimises the need for tactical, reactive control.

The science of density and flow

Crowd science defines the how, where, when and why crowds form and move. It analyses the direct relationship between human psychology, spatial geometry and density. Crowd science focuses on the safety of the crowd and crowd risk analysis. The planning process is fundamental in order to manage people safely. Understanding the audience that will attend the event, what type of person it will attract, the location, the weather and timing of the event. The first phase of the planning process, a calculation of crowd density is required. This calculation is needed to give information on crowd numbers/capacity, pedestrian flow rates and number of emergency exits required. To obtain an estimation of persons filling a large area, crowd managers work with a square metre filled with people. When an area is filled and people start to move in high density crowd, the individual does not have enough space around them and the entire crowd acts as one, moving like a fluid. This occurs at occupancies of about seven persons per square metre. The laws of fluid dynamics form the behaviour of the crowd. Several factors can affect the crowd density and flow rates, pinch points and bottlenecks, crowd managers also consider complexity of routes. Calculating the capacity of an event space to control crowd density is paramount.

The DIM-ALICED framework

As part of risk analysis, it is important to understand how the crowd’s behaviour will be influenced by the environment. A robust crowd management plan is required; professionals utilise the DIM-ALICED model. Developed from global incident analyses, this framework maps out the three primary influences on crowd behaviour — Design, Information and Management — across the six phases of an event: Arrival, Last mile, Ingress, Circulation, Egress and Dispersal.

Design

Crowd managers should be involved in the design phase, this way they can identify, advise the client and address potential issues with the event.  Design is largely concerned with the infrastructure, barriers, queuing system, footpaths, toilets, merchandise and refreshment stands.

Information

Information in this instance is exactly how facts are being provided and conveyed.

• How are we communicating with the audience?
• Is there appropriate signage?
• Social media?

Management

Put simply this is how the event will be managed, or how the crowd will be managed, at each phase.

Arrival

Crowd managers must evaluate how the audience is travelling, where they are coming from and their expected arrival times to prevent sudden, overwhelming surges.

Last Mile

The last mile is the part of the individual’s journey from arrival to the event. Considerations are given to distance, potential bottlenecks and are there any obstacles on the last mile. The last mile, if designed correctly, should control the flow of spectators and should sufficiently direct crowds to the event.

Ingress

Ingress is the entrance phase. Calculate the precise entry capacity to determine how many queuing lanes and barriers (types) are required. Crucially, if security screening or bag checks are present, this impacts the flow of people and must be factored into the overall timing calculations to prevent dangerous bottlenecks at the gates.

Circulation

Once inside, how do people move? How are the routes defined? Potentially how will people move from area to area, from food and beverage stands? Another exceptional risk analysis theory is the RAMP Analysis model; this is suited to the planning of the circulation phase.

Egress

The act of leaving the venue demands as much mathematical precision as entering. Exit widths and flow rates must be calculated to ensure egress systems can comfortably accommodate the mass departure within a set timeframe, avoiding congestion, delays and stress.

Dispersal

The definition of dispersal is “the action or process of distributing or spreading people over a wide area”.  Where will people go, which direction? Ushers may need to encourage people to leave the event area. Another question to ask is, where will the egress leave people? Each phase requires analysis and the easiest way to present this is in the form of a risk matrix.

Ramp Analysis

To add a vital element to this planning, managers overlay a RAMP Analysis (Routes, Areas, Movement and Profile). By integrating a time matrix into RAMP, you can understand how the event and risk shifts hour-by-hour.

• Routes & Areas: From which direction will the crowd approach and depart? How will the physical layout be utilised at peak times?
• Movement: What specific types of movement are expected?
• Profile: What is the demographic of the crowd? Is there a historical precedent for adverse behaviour, or intense rivalry?

The bottom line

Crowd management is achieved by planning and design, that shapes how a crowd moves and behaves. Planning with the aid of Risk Analysis models such as DIM-ALICED and RAMP Analysis ensures that every phase of the attendee journey is engineered for safety, facilitating both the seamless movement and ultimate enjoyment of the crowd.