A Review of Building Evacuation Models - NIST Virtual Library

A.19 EGRESS
Developer: N. Ketchell, AEA Technology, UK
Purpose of the model: The purpose of this model is to determine the evacuation of crowds in a
variety of situations, such as theaters, office buildings, railway stations, and ships 11, 82-84 .
Availability to the public for use: EGRESS is available only on a consultancy basis and the
software is not offered for sale.
Modeling method: This is a behavioral model
Structure of model: This is a fine network system. The floor plan of a building is covered in
cells that are equivalent in size to the minimum area occupied by an occupant. Instead of being
square, like most grid cells, the cell is hexagonal in shape, as shown in Figure A.22. The
2
hexagon has a height equal to h and an area of 3 2 × h . EGRESS holds a default of 5 people
per square meter, which equals a grid spacing of 0.5 m. This can be modified if occupants are
expected to be carrying large objects, etc.
Figure A.22: Example of cells on an egress plan
84, p. 2
Perspective of model and occupant: The model views the occupants as individuals. The
movements of each occupant are carefully monitored throughout the simulation. Each individual
also has certain goals and a specified time period to complete that goal.
The occupants’ perspective of the floor plan is also individual. EGRESS contains a route finding
algorithm that defines the shortest distance from each cell on the floor plan to each specified
region or exit. Then, the behavioral modeling aids in choosing which objective the occupants
moves toward.
Occupant behavior: The occupant behavior is conditional. As long as the objective is still
possible within the time frame allotted, the individual continues to pursue the goal.
The method of behavioral modelling has become simpler since the previous method was found to
cause major issues in the number of decisions made by each occupant. EGRESS provides
groups of occupants with itineraries throughout the evacuation in order to alter objectives/goals,
as shown in Figure A.23. Each objective (example is movement towards the fire for an
A-66