Developments in Tenability and Escape Time Assessment for Evacuation Modelling Simulations

Abstract

Historically, most evacuation simulations have been limited to consideration of a single parameter, the physical movement of escaping occupants during the travel phase of evacuation under non-fire conditions. Considerable research effort has been expended on developing ever more accurate representations of this parameter in simulations, often at the expense of other important aspects, which are usually ignored. In practice, occupant movement during the travel phase represents only one part of a system consisting of a number of key parameters that determine escape and evacuation times during fires in the built environment. Also, evacuation, comprising pre-moment time following warnings, and travel time, is only a subset of escape time, which includes time from ignition to detection and time from detection to the provision of warnings to occupants. In order to simulate the outcome of a fire incident in an occupied enclosure it is important to consider the interactions between the different elements of a system comprising the growing threat from the fire, in terms of available safe escape time (ASET), and the required safe escape time for the occupants (RSET). ASET represents the processes and time involved between ignition and the time when conditions become untenable. RSET represents the processes and time involved between ignition and that when all occupants have reached a place of safety. This chapter discusses the nature and importance of the different parameters involved in ASET and RSET and the interactions between them. Consideration is given to the data and research efforts needed to develop and incorporate functions for the different parameters into comprehensive escape and evacuation simulations, with a number of examples illustrating different aspects and approaches.