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