Efficient evacuation of high-rise buildings is one focus of ongoing safety research at the National Institute of Standards and Technology (NIST). The goal of this work is to identify data-driven changes in building design to improve safety. For experiments involving human egress from high rise buildings, exit data consist of observed occupant exit times t1<t2<...<tn. These events are realizations of a random point process. A point process we have successfully used to model egress at NIST is the Hawkes model (see Reference 3). As a self-exciting model, the Hawkes model captures natural dependencies that occur among evacuees. For example, when a slow-moving occupant on a stair is met, occupants behind either decrease their speed and follow that occupant or move to pass. This behavior significantly affects the exit flow. Results from the Hawkes model indicate that a stair width larger than the normative minimum stair width of 1.12 m specified in the U.S. building codes would speed evacuation by better accommodating natural human interaction.
Merging flows from each floor may be another source of inefficiency in building egress. Specifically, speed and flow rate can be reduced on landings where flows merge. Depending on stair geometries, a merged flow may come to a complete stop and induce queuing, which would slow egress enough to endanger lives. One of the promising opportunities for future research in this area is to study how merging flows affect occupant exit flow by appropriately adapting and extending the Hawkes model.
1. Peacock, R.D., Reneke, P.A., Kuligowski, E.D., Hagwood, C., Movement on stairs during building evacuations. Fire Technology 53, 845-871 (2017).
2. Hagwood, C., Reneke, P.A., Peacock, R.D., Kuligowski, E.D, Incorporating Human Interaction into Stair Egress with an Application to Minimum Stair Width, Fire Technology, 1-21, (2018).
3. Daley, D.J., Vere-Jones, D., An Introduction to the Theory of Point Processes, Vol I. (2002).