A Review of Building Evacuation Models - NIST Virtual Library

A.13 Legion
Developer: Legion International, Ltd., UK
Purpose of the model: The purpose of this model is to aid in space planning and optimization
through the prediction of crowd behavior as an interaction between individuals 66-68 . The model
can be used for a wide variety of applications (i.e. railway and metro stations, airports, and tall
buildings) and needs (i.e. design, refurbishment, and operation and safety assessment).
Availability to the public for use: This model has been commercially available through Legion
International Ltd. since May 2003.
Modeling method: This is a behavioral model.
Structure of model: The Legion model works in a vector 2D continuous space, instead of
superimposing a coarse or fine grid network onto the floor plan. In addition, by providing a
continuous approach to the structure configuration, the model can simulate counterflow,
overtaking, people and obstacle avoidance, and negotiation through crowds. The model refers to
its structure as an “unbounded choice” method. This method explores the possible moves
available to the occupant in vector space which is updated constantly, instead of being
constrained by a set of rules.
Perspective of model and occupant: The model views the occupants as individuals. Each
individual in the model is considered to be a virtual person and is simulated accordingly with
distinct physical and psychological characteristics and objectives.
The occupant’s view of the building is also an individual perspective. This virtual person moves
in a realistic manner. Occupants determine their path based on their perception and information
stored in the space.
Occupant behavior: Artificial Intelligence. Legion views the occupants as intelligent
individuals and social, physical, and behavioral characteristics are assigned probabilistically
from empirically established profiles. The social characteristics include gender, age, culture, and
pedestrian type (i.e. commuter versus tourists) which Legion states shape typical movement
preferences. The physical characteristics addressed are body size. And, the behavioral
characteristics include memory, willingness to adapt, and preferences for unimpeded walking
speeds, personal space, and acceleration. These characteristics make up a profile for each person
and are based on distributions derived from video footage of actual pedestrians.
Also, Legion allows for conditional and probabilistic behavior to be superimposed on the base
model.
Occupant movement: Occupant movement within the model is in agreement with extensive
empirical research performed on the study of crowd movement and behavior. Research teams
have acquired and analyzed video footage of individual and crowd behavior. Movement is based
upon the “least-effort principle,” which means that each individual attempts to minimize
dissatisfaction (defined as the aggregate of frustration, inconvenience, and discomfort). These
A-48