A Review of Building Evacuation Models - NIST Virtual Library

emergency personnel worker) on the itineraries is assigned a time period in which each
individual of the group will attempt to reach it. If during the time period, the preferred objective
is still possible, each person continues to pursue it. If the objective is no longer possible, the
next objective down the list is attempted. The itinerary includes the appropriate delay times for
responding and intermediate delays for
decision making to pursue other options.
Other ways of altering behaviour are
assigning regions which are accompanied
by a delay time when crossing them,
regions which decrease walking speed
when passing them, and regions which alter
the evacuation route assessment. EGRESS
can also incorporate assessing the
fractional toxic doses received by the
occupants in the evacuation, but the
developers state that these are infrequently
used due to their degree of speculation in
the process of modelling such actions.
Occupant movement:
Route finding
People move from cell to cell based on the
“throw of a weighted die.” This can be described as a cellular automata model. The
84, p. 9
Figure A.23: Behavioral modeling in EGRESS
weights/probabilities of the die are calibrated against the speed and flow, as a function of the
density, of the occupants to move them throughout the building. For certain cases, the model can
vary these probabilities for the cells to reflect changes in the evacuation event, such as a region
becoming blocked by smoke. EGRESS contains a route finding algorithm that calculates the
shortest distance from each cell to each exit. With the behavioral modeling in EGRESS, the
individual on any cell chooses which exit to move towards. Multiple travel routes are specified
within the model by assigning each cell a potential number for each of the exits (or attractors as
used by EGRESS). From these index numbers given to each cell, which one of the 6 adjacent
cells surrounding the current hexagonal cell is closer, further away, or the same distance from
the exit can be determined by comparison among the adjacent cells. Cells can be open spaces,
occupied by a person, a portion of a wall or blockage, or an exit/region.
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