Evacuation process simulation
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).
Classification of models
Simulations are based on mathematical models that resemble reality. The calculations are usually carried out using computers. Models are the specification of a certain theory. They can be classified according to the following criteria:
| 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.
Simulation of evacuations
Buildings (train stations, sports stadia), ships, aircraft, tunnels, 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.
Tunnels
Tunnels are unique environments with their own specific characteristics: underground spaces, unknown to users, no natural light, etc. which affect different aspects of evacuees behaviours such as pre-evacuation times (e.g. occupants' reluctance to leave the vehicles), occupant–occupant and occupant–environment interactions, herding behaviour and exit selection.
Ships
Four aspects are particular for ship evacuation:
- Ratio of number of crew to number of passengers,
- Ship motion,
- Floating position
- The evacuation system (e.g., slides, life-boats).
Ship motion and/or abnormal floating position may decrease 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.
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.
Literature
- A. Schadschneider, W. Klingsch, H. Klüpfel, T. Kretz, C. Rogsch, and A. Seyfried. Evacuation Dynamics: Empirical Results, Modeling and Applications. In R.A. Meyers, editor, Encyclopedia of Complexity and System Science. Springer, Berlin Heidelberg New York, 2009. (to be published in April 2009, available at arXiv:0802.1620v1).
- Lord J, Meacham B, Moore A, Fahy R, Proulx G (2005). Guide for evaluating the predictive capabilities of computer egress models, NIST Report GCR 06-886. http://www.fire.nist.gov/bfrlpubs/fire05/PDF/f05156.pdf
- E. Ronchi, P. Colonna, J. Capote, D. Alvear, N. Berloco, A. Cuesta. The evaluation of different evacuation models for road tunnel safety analyses. Tunnelling and Underground Space Technology Vol. 30, July 2012, pp74-84. DOI: http://dx.doi.org/10.1016/j.tust.2012.02.008,
- Kuligowski ED, Peacock RD, Hoskins, BL (2010). A Review of Building Evacuation Models NIST, Fire Research Division. 2nd edition. Technical Note 1680 Washington, US.
- International Maritime Organization (2007). Guidelines for Evacuation Analyses for New and Existing Passenger Ships, MSC/Circ.1238, International Maritime Organization, London, UK.