A Review of Building Evacuation Models - NIST Virtual Library

A.23 BGRAF
Developer: F. Ozel, University of Michigan, U.S.
Purpose of the model: The purpose of the model is to simulate cognitive processes during
evacuation with the use of a graphical user interface 99-102 . The developer recognizes the model
BFIRES-2, of which this model seems to be very similar.
Availability to the public for use: The model is not publicly available at this time. The
developer is working on putting together a CAD-based version of the model, and states that
when that is finished, the model might become available.
Modeling method: This is a behavioral model.
Structure of model: This is a fine network system. Each node, similar to BFIRES, represents
an x,y point on the floor plan. The preference levels are given to spaces/nodes that affect the
movement of the occupant throughout the situation. “Paths” are the lines/distances that connect
the nodes to one another.
Perspective of model and occupant: This model recognizes individuals. The model also keeps
track of the position (x,y coordinates) of the occupants throughout the simulation. The
properties of the occupants are both physical (walking speed, mobility, alertness, smoke
tolerance, and initial location) as well as psychological. Examples of these psychological
properties are the goals that the occupant sets for himself/herself and the probability of these
occurring, the threshold of stress, and the familiarity.
The occupants also have an individual view of the building because the occupant travels a
particular route resulting from a sequence of actions that depend on the preference levels,
environment, and the other occupants in the evacuation.
Occupant behavior: The model attempts conditional behavior. The model incorporates an
episodic structure which is similar to BFIRES. Each episode is identified by a specific goal of
each occupant. When the current goal changes, a new episode begins. The decision process
consists of choosing the next goal, which triggers a new set of actions for the occupant to choose
from. There are also such things as goal modifiers, which are physical, social, or individual
factors that can prompt a change in the current goal. Following all descriptions of the concepts
is a diagram of the BGRAF system (Figure A.24).
Each portion of Figure A.24 is described below:
• Action library: This “library” contains likely actions of occupants during an evacuation.
Action sequences are defined by the goal they serve. Examples of actions are stay in place,
go to the door, go to the fire, go to the alarm, go to the exit, go to the window, go to an
impaired person, turn back, open a door, ventilate a room, etc.
• Goal modifier library: This “library” includes the factors that influence or trigger a change
in goal. The developer notes that these are obtained from studies of actual fires, but no
references are included. Once an occupant reaches the threshold called “information buildup
A-83