|Public Risk Perception of Elevator Evacuation in High-Rise Buildings|
Issue 87: Public Risk Perception of Elevator Evacuation in High-Rise Buildings
By Axel Jönsson & Johan Andersson
Evacuation elevators are desirable because the system poses an opportunity to improve the evacuation of high-rise buildings in several ways, such as:
There are, however, unsolved problems with the introduction of elevators as an emergency escape route. One obvious problem is that people, for most of their lives, have been instructed not to use elevators in emergency situations, but in certain high-rise buildings, they are now expected to disregard these instructions.4
This poses some questions about how evacuees will act in such situations. Will the elevator be regarded as a viable option or will everyone use the stairs? If the evacuees regard the elevator as unsafe, what can be done to change this view?
To answer questions like these, it is necessary to examine the factors that affect individuals' decisions when choosing how to evacuate in a high-rise building. Studies imply that risk perception is a key factor when an individual makes the decision whether or not to initiate an evacuation.5 Therefore, it is natural to expect that this factor also influences individuals' choice of evacuation route, i.e., when they choose the stairs or the elevator during a high-rise evacuation. Risk perceived in a situation depends both on the perceived possibility to control the situation as well as the experienced clarity of the situation.6
A study about evacuation of high-rise buildings was performed at Lund University.7 The aim of the study was to identify how the risks associated with elevators and stairs as means of escape are perceived depending on a number of factors, such as floor number and the building use. Since risk perception was also examined. The study also included an evaluation of different technical systems, that have been proposed in earlier studies,8,9 to aid individuals’ perceptions of the elevator as a possible escape route.
The data collection in the study consisted of a questionnaire survey. The questionnaires were distributed in 10 of Sweden’s 30 tallest buildings, and 573 people responded to the survey. (See Figure 1.) The respondents were people who lived, worked or visited the 10 high-rise buildings, and the questionnaire was answered on-site in the building. The questions included topics such as preferred choice of escape route – stairs or elevators – given a specific scenario. Also, the acceptable waiting time for elevators during evacuation was asked.
The results of the study show that the floor number in the building, i.e., the floor where the respondent was located when filling out the questionnaire, was a crucial factor for the risk perception of the different means of escape. A more detailed analysis shows that perceived risks associated with using elevators as a means of escape are generally greater than for using stairs.
Also, the stairs were perceived as less safe to use in an evacuation if the respondents were located on higher floor levels in the buildings. Similarly, the elevator was perceived as safer to use in an evacuation if the respondents were located on higher floor levels. The relative difference between the different evacuation options was greater at the lower floor levels of the building and lesser at the higher floor levels.
The study also showed that the use of the building was an important factor regarding the risk perceptions assocated with the different means of escape. Respondents who answered the questionnaire in an office building perceived greater risks with the use of an elevator as a means of escape than respondents who answered the questionnaire in residences or hotel buildings. Also a similar relationship was shown in the demographic analysis, where older respondents tended to be more reluctant to use the elevator than the younger ones.
Generally the greatest perceived risk in an evacuation scenario in a tall building was the risk of getting stuck in a queue, both when evacuating using stairs or elevators. This was followed by the perceived risk of fire and smoke entering stairwells, when evacuating with stairs, and the risk of getting stuck in the elevator, when evacuating with elevators.
The fact that the respondents rated the risk of getting stuck in a queue as the greatest perceived risk could explain why the elevators were seen as more risky in the office buildings. Since there can be expected to be more people in the respondents’ direct surroundings in an office building, the queuing risk is reasonably seen as greater in these buildings. This can also explain the results showing very low acceptance for waiting times when using an elevator for evacuation. Only 4% of the respondents answered that they would accept waiting longer than five minutes for an elevator in an evacuation situation.
Also the floor level also was a factor regarding the primary choice of escape route. The study showed that the percentage of people who will evacuate using an elevator varies with floor level, and a correlation was developed to approximate this. This correlation, shown in Figure 2, can be used when modeling elevator usage in buildings with the elevator as a means of escape.
The relationship differs from other studies in similar areas.9,10 This could be explained by the way the study was conducted. In earlier studies, the respondents were given both a hypothetical floor level and a hypothetical scenario. The present study was conducted at the respondents’ actual floor levels, even though the use of a hypothetical scenario could not be avoided.
Also, the study showed that information about what happens in the building during an emergency situation has proven to be a factor for the respondents when trying to improve their acceptance of the elevator as a part of the evacuation route. Thus, the study recommends systems that meet the informational needs of the evacuees, e.g. a spoken (voice) alarm with different messages depending on situation, two-way communications in the elevator and the elevator lobby and also education and information about the elevator. A system with a display that shows expected waiting time for the elevator was shown to be the least appreciated system of the respondents. The reason for the low appreciation of this system is probably due to the evacuee’s reluctant attitude towards waiting.
Axel Jönsson & Johan Andersson are with Brandskyddslaget AB
2nd Quarter 2013 -- Evacuation of Tall Buildings -- Bryan Hoskins, Ph.D.
1st Quarter 2011 -- Symposium Highlights Elevator Use in Building Emergencies – Flashpoints department feature
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