Modelling Human Behaviour & Evacuation in Fire Emergency
Modelling Human Behaviour and Evacuation in Fire Emergency.
Human behaviour during fire emergencies is a complex yet vital aspect of fire protection engineering. It involves the actions, decisions, and responses of individuals and groups when exposed to fire, playing a crucial role in shaping both the fire’s progression and the effectiveness of evacuation procedures. Although predicting human behaviour in such situations poses significant challenges, it is essential for developing reliable fire safety systems, safeguarding occupants, and accurately reconstructing fire events.
When analysing human behaviour in fire scenarios, several key factors must be taken into account:
Occupant Load and Density: The number of people present and how they are distributed within a space greatly affect evacuation flow and the likelihood of congestion. High occupant density can slow movement and increase the risk of trampling.
Occupancy Characteristics (Alone or in Groups): Whether occupants are alone or part of a group influences their decision-making and movement patterns. Group dynamics, such as leadership roles and herding tendencies, can either facilitate or obstruct evacuation efforts.
Building Familiarity: Knowledge of the building’s layout, including exits and alarm systems, is critical for rapid and efficient evacuation. Lack of familiarity can lead to confusion, disorientation, and delays.
Activity and Distribution of Occupants: The nature of activities occupants are engaged in, along with their location within the building, impacts initial response times. Those who are asleep or physically incapacitated may face substantial delays in evacuating.
Alertness and Awareness: Levels of alertness, which may be influenced by factors such as fatigue, intoxication, or distraction, significantly affect how quickly individuals perceive and respond to fire alarms and warnings.
Physical and Cognitive Capacities: Physical impairments (such as reduced mobility) and cognitive limitations (including disabilities or age-related challenges) can hinder evacuation speed, route selection, and comprehension of emergency instructions.
Social Affiliation and Group Dynamics: Social relationships and group affiliations can shape evacuation behaviour, with some individuals prioritizing the safety of group members over their own, potentially delaying evacuation.
Demographic Factors (Gender and Age): Age and gender can influence physical capabilities and behavioural responses during fire emergencies. For instance, children and the elderly may need additional support to evacuate safely.
Figure 1 The behavioural process of occupant response in building fire.
Evacuation/Egress Modelling
Egress modelling is a specialized field within architectural and fire safety engineering that focuses on simulating and analysing human movement during emergencies, particularly building evacuations. By leveraging mathematical models and computer simulations, it predicts and optimizes occupant flow as individuals exit a structure during crises such as fires.
To achieve accurate predictions, egress models take several critical factors into account:
- Building Layout: The configuration of rooms, corridors, and other internal spaces that influence evacuation routes.
- Occupant Behaviour and Movement Speeds: The way individuals respond and move during emergencies, including differences in walking speeds and decision-making processes.
- Exit Locations: The number and strategic placement of exits to support efficient evacuation.
- Signage: The visibility and effectiveness of directional signage guiding occupants toward exits.
- Capacity of Pathways and Exits: The maximum number of occupants that can safely pass through corridors, doorways, and other egress routes without congestion.
- Impact of Hazardous Smoke: The influence of smoke and other hazardous conditions on visibility and mobility during evacuations.
By evaluating these elements, egress modelling contributes to designing safer buildings and spaces that enable swift and secure evacuations. Additionally, it plays a crucial role in refining evacuation plans, identifying potential bottlenecks and hazards, and ensuring compliance with fire safety regulations. Ultimately, egress modelling enhances occupant safety and survivability during emergencies.
Most Popular Evacuation Modelling Software Packages:
Pathfinder (Thunderhead Engineering): A leading tool for simulating pedestrian movement and evacuation, renowned for its ability to handle complex building geometries and large crowds. It offers advanced steering modes to replicate individual decision-making during emergencies.
EvacSim (Arup): Designed for simulating pedestrian flow and evacuation in a variety of building types and transportation hubs. It excels in capturing intricate aspects of human behaviour during evacuations.
STEPS (Movement Strategies): A robust modelling tool for analysing pedestrian dynamics and evacuation processes in diverse settings, including large venues and urban areas.
MassMotion (Oasys): Offers high-level simulations of crowd behaviour and evacuation in intricate buildings and urban environments, featuring advanced visualization tools for enhanced analysis.
Building EXODUS (University of Greenwich): A widely adopted evacuation modelling software that simulates human movement and behavioural patterns in buildings, grounded in extensive research.
Legion (Legion Technologies): A sophisticated solution for simulating pedestrian flow and evacuation in complex structures and transportation hubs, notable for its precise behavioural modelling.
Simulex: Focuses on simulating and analysing occupant movement and evacuation in buildings, supporting the evaluation and enhancement of evacuation strategies.
Figure 2 Evacuation Simulations results showing Occupant Travel Path. (Pathfinder Simulation.)
Human Behaviour Modelling Approaches.
1. Agent-Based Simulation
Pathfinder utilizes an advanced agent-based simulation approach, modelling each occupant as an individual entity with distinct decision-making capabilities. Key features of this approach include:
- Variable Walking Speeds: Speeds are adjusted based on demographic factors such as age groups (adults, elderly, children).
- Pre-Movement Time Distributions: Incorporates stochastic distributions to represent varying response delays before movement begins.
- Exit Choice Algorithms: Determines exit selection based on factors such as the shortest path, familiarity with routes, and social behaviours.
- Dynamic Flow Adjustments: Occupant speed dynamically adapts to changes in crowd density and reduced visibility caused by smoke.
2. Flow-Based Simulation
The flow-based model operates on hydraulic principles, treating occupant movement as a continuous flow rather than as individual agents. This computationally efficient approach is ideal for large-scale buildings where movement patterns are more predictable. Key components include:
- Flow Rate Constraints: Evacuation flow rates are governed by door and corridor capacity limits, following guidelines from the SFPE Handbook.
- Queue Formation Dynamics: Models the accumulation of occupants at bottlenecks, such as narrow exits, which can slow overall evacuation progress.
- Conveyor Belt Model: Represents linear occupant movement, making it well-suited for environments like stadiums, large office buildings, and transportation hubs.
Figure 3 Pathfinder Agent-based Evacuation Simulation Results showing occupant density (occs/m2).
Applications and Benefits of Evacuation Modelling
Optimizing Building Design: Evacuation modelling supports architects and engineers in designing buildings with efficient layouts, well-placed exits, and unobstructed pathways. This minimizes evacuation times and reduces the risk of congestion during emergencies.
Developing Effective Evacuation Plans: It enables emergency planners to design and refine evacuation procedures by simulating various scenarios and addressing potential challenges, ensuring smooth and orderly evacuations.
Ensuring Code Compliance: The modelling process helps demonstrate that building designs and evacuation strategies align with fire safety regulations and building codes, streamlining the approval process.
Enhancing Emergency Preparedness: By identifying potential risks and vulnerabilities, evacuation modelling plays a crucial role in developing comprehensive emergency response plans and training programs, ultimately improving overall emergency readiness.
Limitations of Evacuation Modelling
Uncertainty in Human Behaviour: While evacuation models are based on predefined behavioural patterns, real-life human actions during emergencies can be unpredictable. Variables such as panic, hesitation, and social influences are challenging to simulate with complete accuracy.
Simplifications and Assumptions: To streamline simulations, models often simplify building layouts, fire and smoke effects, and environmental conditions. However, these simplifications may not fully capture real-world complexities, such as structural failures or evolving hazards.
Reliance on Data Quality: The accuracy of evacuation modelling is heavily dependent on the quality of input data, including crowd movement patterns and response times. Incomplete or inaccurate data can compromise the reliability of the results.
Conclusion
Evacuation modelling is essential for improving safety by offering valuable insights into human behaviour during emergencies. Despite its limitations, continuous advancements in technology, data analysis, and behavioural research are enhancing the accuracy and reliability of these simulations. As urbanization and population density continue to rise, effective evacuation planning becomes increasingly critical, solidifying the role of evacuation models as indispensable tools for protecting lives.