Evacuation process simulation

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Evacuation simulation is a method to determine evacuation times for areas, buildings, or vessels. It is based on the simulation of crowd dynamics and pedestrian motion.

The distinction between buildings, ships, and vessels on the one hand and settlements and areas on the other hand is important for the simulation of evacuation processes. In the case of the evacuation of a whole district, the transport phase (see emergency evacuation) is usually covered by queueing models (see below).

1 Classification of models
2 Simulation of evacuations
- 2.1 Ships
- 2.2 Aircraft
3 External links

[edit] Classification of models

Simulations are the based on mathematical models that resemble reality. The calculations are usually carried out using computers. Models are the specification of a certain theory. The can be classified according to the following criteria:

(Gershenfeld, 1999):

specific	--	general
phenomenological	--	first principles
discrete	--	continuous
numeric	--	analytic
stochastic	--	deterministic
quantitative	--	qualitative
macroscopic	--	microscopic

Simulations are not primarily methods for optimization. To optimize the geometry of a building or the procedure with respect to evacuation time, a target function has to be specified and minimized. Accordingly, one or several variables must be identified which are subject to variation.

Queueing models belong to the macroscopic models which are based on the graphical representation of the geometry. The movement of the persons is represented as flow on this graph. Microscopic models on the other hand are based on a detailed representation of geometry and population. If the individuals are autonomous and interact with each other, these models are called Multi-Agent-Systems. Stochastic parameters describe the agents' movement and decisions and represent influences not further specified or which cannot be quantified directly and have to be calibrated via comparison with empirical data. Analytic results are very hard to obtain for social systems. General models can be applied to the evacuation of buildings, aircraft, and ships alike.

[edit] Simulation of evacuations

Buildings (train stations, sports stadia), ships, aircraft, and trains are similar concerning their evacuation: the persons are walking towards a safe area. In addition, persons might use slides or similar evacuation systems and for ships the lowering of life-boats.

[edit] Ships

Three aspects are particular for ship evacuation:

Ratio of number of crew to number of passengers,
Ship motion,
The evacuation system (e.g., slides, life-boats).

Ship motion decreases the ability to move. This influence has been investigated experimentally and can be taken into account by reduction factors.

The evacuation of a ship is divided into two separate phases: assembly phase and embarkation phase.

[edit] Aircraft

The Federal Aviation Administration requires that aircraft have to be able to be evacuated within 90 seconds. This criterion has to be checked before approval of the aircraft.

The 90-second rule requires the demonstration that all passengers and crew members can safely abandon the aircraft cabin in less than 90 seconds, with half of the usable exits blocked, with the minimum illumination provided by floor proximity lighting, and a certain age-gender mix in the simulated occupants.

The rule was established in 1965 with 120 seconds, and has been evolving over the years to encompass the improvements in escape equipment, changes in cabin and seat material, and more complete and appropriate crew training.

Very recently, a meaningful move has modified the up to now classical approach with new exit types, new conditions to perform or assess evacuation demonstrations, etc, although some questions are still open. These capacities are completed in the regulations with a series of statements regarding additional interactions and limitations.

The unique objective of the demonstration is to show that the airplane can be evacuated in less than 90 seconds under the aforementioned conditions. So the demonstration provides only a benchmark for consistent evaluation, which allows for comparisons among diverse seating arrangements or modifications in existing airplanes. Obviously, the demonstration can not represent accident scenarios and is not intended for system optimization.