AnalysisWTC escape behavior may lead to changes in building code, work-place rules

Published 17 February 2006

Most of the studies of the 9/11 Twin Towers attack concentrated on first responders operational issues (for example, communication interoperability), and the structural qualities of and building materials used in the towers. As we reported a few days ago, Edwin Galea, a fire safety expert from the University of Greenwich, outside of London, and six behavioral psychologists are now in New York to collect the stories of the people who made it out of the towers. The purpose: The see whether the behavior of people under disaster conditions can yield ideas about building design and work place practices.

Some observations have already been made:

When fleeing for their lives, people in the towers listened to the same line managers who directed their everyday work. So perhaps managers ought to be trained as fire wardens

People report that staircases were littered with high heels, suggesting that women bring sensible shoes to work in case they need to get out fast

High-rise designs assume that people react to an emergency fairly quickly, but in the twin towers some apparently waited anywhere between ten minutes and an hour before leaving

Regulations assume that people evacuate as individuals, but in the WTC many descended in groups — but groups move only as fast as their slowest member

Did employees at strictly hierarchical firms wait for orders instead of just heading for the exits?

Different people perceived risk differently

The most crucial questions relate to what happened on the stairs. This is important because one of the biggest riddle from the WTC stairwells is the question why the evacuation was so slow. Engineers assume that people in a high-rise emergency descend three to four stories a minute, but people on 9/11 managed only half that speed. There may have been several contributing factors:

Density of the crowds

The counter flow of rescuers coming up the same stairwells

The width of the stairs

Lack of light on most floors

Evacuees’ physical condition: A surprisingly high proportion of evacuees were slowed by a disability, bad heart, asthma, bad knees, or obesity

Slow, obese walkers pose major problems in evacuation: They slow down others, they may be too wide to pass, and many exhibit what experts call “exaggerated body sway.” If a large person gets injured in an evacuation, the problems are compounded as they are more likely to block the stairs and require more rescuers to lift them out. Obesity is becoming a major issue in the United States, and if it is the case that people are moving more slowly these days, it means either that buildings have to last longer in a fire (leading to costlier fireproofing), the stairs have to be wider (leading to less rentable space), or there has to be an alternative provided for those too slow to walk down.

-read more in this report; to learn more about Galea study, and to sign up for an interview if you are a WTC survivor, go to University of Greenwich WTC Evacuation Study Web site