Enrico Ronchi

Fire evacuation in high-rise buildings: a review of human behaviour and modelling research

A review of literature related to fire evacuation in high-rise buildings was carried out with the following objectives, (1) to identify the key behavioural factors affecting the performance of people during a fire in a high-rise building, the singularities associated to this type of buildings and areas of future research; (2) to review the procedures and strategies currently adopted in high-rise buildings; (3) to review and analyse the capabilities of evacuation models by reviewing their current characteristics and applications in the context of high-rise building evacuations. The review included both findings on human behaviour in high-rise buildings and modelling techniques and tools. Different categories of building use were taken into account, namely office buildings, residential buildings and health care facilities. The individual or combined use of different egress components was analysed. Egress components include the use of stairs, elevators as well as alternative means of escape (e.g., sky-bridges, helicopters, etc.). The effectiveness of the egress components is strongly affected by the building use and the population involved. The review shows that evacuation models can be effectively employed to study relocation strategies and safety issues associated with high-rise buildings. The suitability of egress models for high-rise building evacuations is associated with their flexibility in representing different egress components and complex behavioural processes. The review highlights that there is not a definitive model to be used but that the predictive capabilities of evacuation modelling techniques would be enhanced if more than one model is employed to study different egress aspects. Future research and model developments should focus on the study of the impact of staff actions, group dynamics and people with disabilities. Given the increasing height of buildings and the gradual reduction in the physical abilities of the population, the effects of fatigue on evacuation need further studies.

Virtual reality for fire evacuation research

Virtual reality (VR) has become a popular approach to study human behavior in fire. The present position paper analyses Strengths, Weaknesses, Opportunities, and Threats (SWOT) of VR as a research tool for human behavior in fire. Virtual environments provide a maximum of experimental control, are easy to replicate, have relatively high ecological validity, and allow safe study of occupant behavior in scenarios that otherwise would be too dangerous. Lower ecological validity compared to field studies, ergonomic aspects, and technical limitations are the main weaknesses of the method. Increasingly realistic simulations and other technological advances provide new opportunities for this relatively young method. In this position paper, we argue that VR is a promising complementary laboratory tool in the quest to understand human behavior in fire and to improve fire safety.

The validation of evacuation simulation models through the analysis of behavioural uncertainty

Both experimental and simulation data on fire evacuation are influenced by a component of uncertainty caused by the impact of the unexplained variance in human behaviour, namely behavioural uncertainty (BU). Evacuation model validation studies should include the study of this type of uncertainty during the comparison of experiments and simulation results. An evacuation model validation procedure is introduced in this paper to study the impact of BU. This methodology is presented through a case study for the comparison between repeated experimental data and simulation results produced by FDS+Evac, an evacuation model for the simulation of human behaviour in fire, which makes use of distribution laws.

An Evacuation Decision Model based on perceived risk, social influence and behavioural uncertainty

The behaviour of people in the first stage of an evacuation can have a significant impact on the time required to reach a safe place. This behaviour is known in literature as pre-evacuation behaviour and it has been studied for many different evacuating scenarios. Despite the large number of studies, the representation of this behaviour is often oversimplified in most of the existing evacuation models. This paper aims to introduce a novel Evacuation Decision Model, allowing predicting the pre-evacuation state of an evacuee among three possible states (normal, investigation and evacuation) considering perceived risk for an evacuation scenario. The proposed model assumes that evacuees’ perceived risk is affected by several environmental and social cues as well as by demographics and personal characteristics of evacuees. The concept of behavioural uncertainty is also included in the model and a formulation to calibrate the proposed model using a likelihood function is then provided.

A dynamic approach for the impact of a toxic gas dispersion hazard considering human behaviour and dispersion modelling

The release of toxic gases due to natural/industrial accidents or terrorist attacks in populated areas can have tragic consequences. To prevent and evaluate the effects of these disasters different approaches and modelling tools have been introduced in the literature. These instruments are valuable tools for risk managers doing risk assessment of threatened areas. Despite the significant improvements in hazard assessment in case of toxic gas dispersion, these analyses do not generally include the impact of human behaviour and people movement during emergencies. This work aims at providing an approach which considers both modelling of gas dispersion and evacuation movement in order to improve the accuracy of risk assessment for disasters involving toxic gases. The approach is applied to a hypothetical scenario including a ship releasing Nitrogen dioxide (NO2) on a crowd attending a music festival. The difference between the results obtained with existing static methods (people do not move) and a dynamic approach (people move away from the danger) which considers people movement with different degrees of sophistication (either a simple linear path or more complex behavioural modelling) is discussed.

Movement on Stairs During Building Evacuations

The time that it takes an occupant population to reach safety when descending a stair during building evacuations is typically estimated by measureable engineering variables such as stair geometry, speed, stair density, and pre-observation delay. In turn, engineering models of building evacuation use these variables to predict the performance of egress systems for building design, emergency planning, or event reconstruction. As part of a program to better understand occupant movement and behavior during building emergencies, the Engineering Laboratory at the National Institute of Standards and Technology (NIST) has been collecting stair movement data during fire drill evacuations of office and residential buildings. These data collections are intended to provide a better understanding of this principal building egress feature and develop a technical foundation for future codes and standards requirements. NIST has collected fire drill evacuation data in 14 buildings (11 office buildings and 3 residential buildings) ranging from six to 62 stories in height that have included a range of stair widths and occupant densities. A total of more than 22000 individual measurements are included in the data set. This report provides details of the data collected, an analysis of the data, and examples of the use of the data. The intention is to better understand movement during stair evacuations and provide data to test the predictive capability of building egress models. While mean movement speeds in the current study of 0.44 m/s ± 0.19 m/s are observed to be quite similar to the range of values in previous studies, mean local movement speeds as occupants traverse down the stairs are seen to vary widely within a given stair, ranging from 0.10 m/s ± 0.008 m/s to 1.7 m/s ± 0.13 m/s. These data provide confirmation of the adequacy of existing literature values typically used for occupant movement speeds and provide updated data for use in egress modeling or other engineering calculations. (Less)

Dissuasive exit signage for building fire evacuation

This work presents the result of a questionnaire study which investigates the design of dissuasive emergency signage, i.e. signage conveying a message of not utilizing a specific exit door. The work analyses and tests a set of key features of dissuasive emergency signage using the Theory of Affordances. The variables having the largest impact on observer preference, interpretation and noticeability of the signage have been identified. Results show that features which clearly negate the exit-message of the original positive exit signage are most effective, for instance a red X-marking placed across the entirety of the exit signage conveys a clear dissuasive message. Other features of note are red flashing lights and alternation of colour. The sense of urgency conveyed by the sign is largely affected by sensory inputs such as red flashing lights or other features which cause the signs to break the tendencies of normalcy.

Basic Concepts and Modelling Methods

Try to imagine a fire emergency evacuation. What is the first image that you have in your mind? Here there are some guesses. Probably a parent running inside a house trying to rescue her children, but not managing since she is too scared? An old man stuck crying in a corner of a room with flames and smoke all around him? Or a group of people crushing aggressively against each other in order to get out of a building through a very small exit door? Almost surely you have thought about people shouting and screaming for help, without doing any constructive actions. Well, these scenarios represent a significant minority of what a fire evacuation generally is. When we think about a fire emergency, we often think about people losing their rationality, rushing irrationally in search of an exit or searching desperately for help. Nevertheless, researchers generally do not agree with this interpretation. This misconception comes from the public opinion, in which a fire emergency is often linked to the word “panic”. Human behaviour in fire emergencies used in media accounts and survivors’ statement is generally associated with panic behaviour. In contrast with this stereotype, the concept that a fire might cause panic has been abandoned by the scientific community [1]. The definition of panic itself has been largely questioned in several research studies [2, 3]. Feelings such as anxiety and stress may occur during a fire emergency, but they do not generally lead to irrational or anti-social behaviours [1]. Evacuees generally tend to behave rationally, with non-rational and anti-social behaviours occurring in very rare occasions, mostly in very extreme scenarios in which the probability of surviving perceived is extremely low [2]. In fact, most people do not develop shock reactions, and tend to act in accordance to what they think is in their best interest, given the limited understanding they have of the situation.

Variable Message Signs for road tunnel emergency evacuations

This paper investigates the design of Variable Message Signs (VMS) as a way-finding aid for road tunnel emergency evacuations. The use of the Theory of Affordances is suggested to provide recommendations on the design of VMS. A preliminary evaluation of 11 selected VMS systems was performed and 6 of them were further evaluated using an affordance-based within subject stated-preference questionnaire administered to a sample of 62 participants. Results are used to provide recommendations on the characteristics of the VMS systems, such as (1) size of the sign (large or small); (2) use of flashing lights; (3) colour scheme; (4) message coding (i.e., text, pictograms or a combination of them). The best performing VMS features for road tunnel emergency evacuation included the use of larger signs, flashing lights, the combination of emergency exit pictorial symbol in green in one panel and text in amber in the other panel.

Assessment of Total Evacuation Systems for Tall Buildings

This report focuses on the use of egress models to assess the optimal strategy in the case of total evacuation in high-rise buildings. A model case study made of two identical twin towers linked with two sky-bridges at different heights has been simulated. The towers are 50 floor high-rise buildings including both vertical and horizontal egress components, namely stairs, occupant evacuation elevators (OEEs), service elevators, transfer floors and sky-bridges. The total evacuation of the single tower has been simulated employing seven possible strategies. The configuration of the egress components is depending on the evacuation strategy under consideration. The strategies include either the use of only one type of vertical egress components (stairs or elevators), or a combination of vertical components (stairs and elevators) or a combination of vertical and horizontal components (stairs, elevators, transfer floors, and sky-bridges). This report presents the general characteristics of the model case study, i.e. the layout of the building and the available egress components in relation to the strategy employed. The evacuation strategies have been simulated employing a continuous model (Pathfinder). In order to provide a cross validation of the results produced by Pathfinder, a fine network model (STEPS) has been employed to simulate the base case (only stairs available for the evacuation) and one scenario including the use of OEEs. The comparison between the models has been made employing specified calculations, i.e. the configuration of the inputs of the models is based on complete information about the model geometry, occupant characteristics, etc. Results show that the range of variability of the results between the two sub-models for stair and elevator modelling allows performing a relative comparison between the evacuation strategies. Differences are dependent on the modelling approaches and the sub-models for stairs and elevators employed by the models. The relative comparison between the strategies has been made using Pathfinder. Strategies involving the use of Occupant Evacuation Elevators (OEEs) are not effective if not linked to appropriate information to occupants about elevator usage, i.e. the accepted waiting time for elevators is lower than 10 minutes. The strategy employing only OEEs for the evacuation is the most efficient strategy. If occupants use sky-bridges to evacuate the building, evacuation times would be significantly lower than the strategies involving the use of stairs only or a combination of elevators and stairs without appropriate information to the evacuees. (Less)