A Review of Building Evacuation Models - NIST Virtual Library

Fire
Influence
Smoke
Influence
Proximity
Checks
Flocking
Influence
DEAD!
Below Trigger
Health Check
Investigate
Below Trigger
Fire Proximity
OK
Route Choice
Limited
Above Trigger
Evacuate
Figure A.28: The VEgAS model
112, p. 42
Within VEGAS, behavior is simulated as a chaotic process. The theory of “anti-chaos” is used
to outline the order in which chaotic systems can develop. The developer uses the example of
bird colonies to explain further. When part of a closer-packed group, bird colonies display group
characteristics of ordered societies, and yet have random behaviors individually. The developer
notes that “the ‘order of chaos’ theory explains the behavior as the net effects of complex
decision making processes having a finite probabilistic outcome for the group as a whole.”
According to Gwynne, the model applies behavior rules dependent upon 1) an objective/goal, 2)
a set of constraints (the occupants attempt to maintain a minimum distance between themselves
and others), and 3) a motivation (the occupants attempt to maintain unimpeded velocity).
VEGAS also uses “proximity logic” to modify behavior. Instead of calculating movement speed
based on density, the model simulates movement speed based on “proximity logic,” which is the
location of the occupant with respect to other objects in the simulation. Also, when a group of
occupants move toward an exit, the occupants who have encountered that group will also move
in the same direction, known as the flocking algorithm. The model also includes an effective
width model.
A-102