"In Emergency, Please Use the Elevators" -- A Sign in the Future?

Summary of learning from Human Movement in Fire and Related Emergencies workshop held at Engineer’s Australia, West Perth, 10 December 2008

The above instruction in the title of this article makes no sense to high rise safety traditionalists, but there is a paradigm shift sweeping the Globe in the science of tall building emergency egress (TBEE), headed by the research of Jake Pauls, CPE. It appears both elevators and stairways have relevance and applicability in TBEE, breaking a generations-old rule.

The role of human behaviour in TBEE is now being considered and foremost experts on the topic are not just fire safety engineers, but ergonomists, psychologists and risk consultants.

One of the key findings in this area, particularly on the back of the September 11 World Trade Center disaster, is we must ‘carefully confirm the relevance of prevailing data’[1] we’ve always assumed to be correct. 9/11 smashed a lot of the theory regarding TBEE. For instance, descent speeds down stairways were actually only half that which were designed, and the ability to get people out of buildings was significantly overestimated.

One major reason for this has been stairway design, including stair width. The predominant stair width of 1,120 mm (44”) is the alleged cause of much of the flow rate problem. It is recommended that stair width be 1,420 mm (56”) to significantly increase flows during emergencies. This 27 percent increase in width delivers a 38 percent increase in flow rate, suggesting the optimal result for a Level of Service[2] at “Level E”.[3] It is alleged that even increasing the width of stairways to 1,220 mm (48”) brings significant improvement (but 1,420 mm is optimal).

As a rule-of-thumb a 1,000 mm stair width will allow sixty (60) people to flow through per minute, or one per second.

Another major reason for the gross overestimation of TBEE effectiveness is due to our physical size, fitness and fatigue factors; obesity is rapidly becoming an epidemic that is having a direct impact on TBEE.

Sixty to seventy (60-70) percent of Americans are overweight and thirty (30) percent are obese, and Australia is not far behind in second place, followed by Canada, the UK, France and Japan. With large people, not only is there less room, the added factors of lack of fitness and fatigue come into play. In extreme cases, there have been stories of three or four fire fighters required to move one person to safety.

Obesity is not only a public health crisis. Such is the extent of this problem, grossly overweight people are now surpassing the mobility impaired as the major issue in overall TBEE.

A further problem relating to obesity is larger people have a greater propensity for slips and falls down stairs.

Another issue is the factor of “human sway.” Until recently, human sway[4] was not considered. Ironically, we sway more as we slow down. This means as the flow down stairways slows down due to congestion, there is the compounded effect of more sway reducing the available space.

“Traffic lanes work for cars, not for people,” was cited. People also don’t adhere to the rules of neatly uniformed road traffic. Not surprisingly, studies indicate human behaviour during evacuation is hard to predict.

Six (6) percent of people have major difficulty using stairs, besides there are practical difficulties in evacuating tall buildings, including the time required. It takes approximately ten times longer to walk down the stairs of tall buildings than it does using an elevator.

British Standard BS 5588:1999 is cited as a remarkably relevant document regarding its benchmark standards, but it has only been adopted in the UK, Hong Kong and Singapore. The rest of the world lags behind this Standard regarding stairway design, complete with lobby and dedicated fire elevators.[5]

Elevators, together with stairways, are now being considered in both phase one and phase two of TBEE’s. Phase one is the initial evacuation of the residents of buildings and phase two is the staging and mobilisation for fire crews in rescue and recovery of remaining evacuees.

The Eureka Tower in Melbourne is a building employing a “Life Safety Strategy”[6] with combined elevator/stairway methodology for TBEE, with two staging areas, at the 52nd and 24th floors.

In brief

Whilst it is not yet considered as recommended that elevators be used during multi-storey evacuations, there is a paradigm shift occurring and strategies for the combined use of elevators and stairs could become the norm in years to come.

Use of elevators for evacuating residents of buildings (phase 1) and staging and mobilisation for fire crews in rescue and recovery (phase 2) is already in place in some countries, including one example cited above in Australia.

This information has relevance to anyone who regularly inhabits buildings of any more than a few floors to one as high as 200 storeys tall.

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ENDNOTES:
[1] This was a refrain repeated during Mr. Peter Johnson’s presentation.
[2] The concept of Level of Service (LOS) was developed by John J. Fruin, Ph.D. LOS “is a measure-of-effectiveness by which traffic engineers determine the quality of service on elements of transportation infrastructure. Whilst the motorist is, in general, interested in speed of his journey, LOS is a more holistic approach, taking into account several other factors.” See http://en.wikipedia.org/wiki/Level_of_service for further information.
[3] “Level E” flows are the most efficient rate of flows for high density traffic whether pedestrians or vehicles. At “Level F” for instance, the congestion slows the rate of flow.
[4] “Human Sway” is said to be the swaying effect of a person moving their weight from one foot to another requiring increased space particularly at the shoulders. This significantly decreases overall flows due to the impact on limited space and other people.
[5] Reference was made to parts 5 and 8 of this Standard titled: Fire precautions in the design, construction and use of buildings.
[6] Part of the strategy is “to protect in place,” ensuring a self-sustaining ‘safety in design’ as part of TBEE.