Pre-movement time

Pre-movement time, also called pre-travel activity time or pre-evacuation time, \(t_{\mathrm{pre}}\) [s], is the interval between the alarm or first cue and the first deliberate movement towards safety. It is a term of the required safe escape time (RSET; see ASET and RSET).

Definition as published

The Society of Fire Protection Engineers (SFPE) Handbook defines \(t_{\mathrm{pre}}\) as the interval between the time at which a general alarm or warning is given and the time at which the first deliberate evacuation movement is made, and splits it into a recognition time, from perceiving the alarm to interpreting it as an emergency, and a response time, from recognition to the first move (Gwynne and Boyce 2016, Ch. 64). ISO/TR 16738:2009 (§5.7) uses the same two elements and distinguishes the pre-travel time of the first occupants from the distribution of pre-travel times over the whole group. There is no equation for \(t_{\mathrm{pre}}\): it is taken from observed distributions.

Why it is long

ISO/TR 16738 (§5.4) reports that the pre-travel activity phase can often be the longest part of the total escape time. Response time includes activities such as fighting the fire, warning others, gathering family members, dressing, collecting belongings and calling the fire service (Ch. 64). Kuligowski (2016, Ch. 58) explains these delays with the Protective Action Decision Model, in which environmental cues such as the sight of smoke and social cues such as warnings interrupt normal activity only if they are perceived as a threat; the occupant then seeks more information, protects people or property, or resumes normal activity, depending on the perceived threat and on whether protective action seems feasible.

The data

Lovreglio, Kuligowski, Gwynne and Boyce (2019) assembled pre-evacuation times from 9 fire incidents and 103 evacuation drills, covering 13 591 evacuees in 16 countries, grouped by occupancy type and clustered to identify sub-groups. They fitted gamma, log-normal, log-logistic and Weibull distributions, all two-parameter, positive and right-skewed, for use as model inputs (their Eqs. 2–5). The database extends the tables of Gwynne and Boyce (2016, Ch. 64). A corrigendum was published in 2019. ISO/TR 16738 (Annex E) gives guidance and default pre-travel times from published data.

Known limits

Drills make up 103 of the 112 data sets, so the database describes drills far more than fires. The authors could not definitively establish the factors that generated the clusters, and advise users to pick the occupancy and cluster closest to their case and to consult the original sources. Pre-movement and travel times within an enclosure interact, so the two distributions cannot simply be added (ISO/TR 16738, §7).

The corrigendum corrects the log-normal a parameter in Tables 3, 5, 7, 9, 11, 13, 15, 17 and 18. Fits within a cluster have R² as low as about 0.55 (Business Cluster 1), and the authors state R² must not be used to choose between clusters.

Sources

• ISO (2009). ISO/TR 16738:2009 Fire-safety engineering — Technical information on methods for evaluating behaviour and movement of people, §5.4, §5.7 and §7. ISO, Geneva. iso.org/standard/42887. Read from the public preview.
• Gwynne, S. M. V., & Boyce, K. E. (2016). Engineering data. SFPE Handbook of Fire Protection Engineering, 5th ed., Ch. 64, 2429–2551. doi:10.1007/978-1-4939-2565-0_64
• Kuligowski, E. D. (2016). Human behavior in fire. SFPE Handbook of Fire Protection Engineering, 5th ed., Ch. 58, 2070–2114. doi:10.1007/978-1-4939-2565-0_58
• Lovreglio, R., Kuligowski, E., Gwynne, S., & Boyce, K. (2019). A pre-evacuation database for use in egress simulations. Fire Safety Journal, 105, 107–128. doi:10.1016/j.firesaf.2018.12.009. Corrigendum: Fire Safety Journal, 108, 102829. doi:10.1016/j.firesaf.2019.102829
• Lovreglio, R., Ronchi, E., & Nilsson, D. (2015). A model of the decision-making process during pre-evacuation. Fire Safety Journal, 78, 168–179. doi:10.1016/j.firesaf.2015.07.001 (further reading; not summarised here).

How pyFDS-Evac uses this: the presets and their sources are in Coming from FDS+Evac › Pre-movement parameters, the scenario keys in Scenario JSON, and a worked ensemble in the RSET ensemble how-to.

How it is verified: the pre-movement row of the Verification index.