Building Evacuation: Two Different Approaches
E M Cepolina, University of Pisa, IT
For building emergencies and evacuations the risk of disaster is measured by the building evacuation time, which is the time to escape needed to the last pedestrian for leaving the building.
The ?Human Behaviour in Fires? report underlines that the time to escape should take into account reaction to alarm time as well as the time to travel to and through exits: it was found that the people?s reaction time to an alarm is as (if not more) important as the time it takes physically to reach an exit. In this paper we will focus on the factors affecting this second contribution and on the devices for reducing it.
The physical time for escaping the building strictly depends on the chaos in the building that is a direct consequence of the human irrational behaviour that typically emerges in panic situations.
In building evacuation irrationality in human behaviour could affect both the exit choice behaviour and the dynamic of pedestrian flow.
For reducing the risk of disaster due to panic it is possible to operate in two different but complementary ways:
1. controlling pedestrian behaviour in such a way to make the best possible use of a given building.
2. adapting the building environment to pedestrian behaviour and making it as much as possible suitable to spontaneous evacuation process;
The first approach assumes an obedient building population and through optimisation network models evacuation plans are determined. The optimality criterion used for defining evacuation plans should be ?minimum travel time?, rather than minimum geometric distance - which usually national recommendations refer to. The network optimisation models aimed to identify, among all the possible evacuation plans, the one that minimises the building evacuation time will be reviewed in this paper. Queuing network models as well as a methodology which uses a mesoscopic model for the dynamic network loading will be reported.
It?s possible to define off-line a set of evacuation plans for a given building: each one suitable for a specific scenario. Depending on the kind of threat that determines the emergency evacuation, on where the threat occurs within the building and on the population distribution within the building, one of the evacuation plans in the set will be implemented as soon as the evacuation starts.
Evacuation plans allow to make the best use of a given building ?imposing? to the building population the paths people have to follow. Increasing the people?s confidence and awareness on the actions to take is therefore a critical issue in this approach.
The second approach requires a deep understanding of pedestrian behaviour in panic situation and through the simulation of a spontaneous evacuation, critical points where poor design of architectural spaces and/or the sign system cause disorientation and confusion are identified.
Models have been developed attempting to represent realistic human behaviour as diverse as reaction to smoke, individual structural knowledge, reaction to communication, reaction to signage, affiliative behaviour, occupant motivation and queue recommitment behaviour.
Architectural spaces and sign systems could be redesigned in such a way to accommodate spontaneous evacuations.
The application fields for the different approaches will be searched. A survey of the theoretical models proposed in literature for dealing with evacuation, as well as an overview of recommendations and laws will be presented.
Association for European Transport