Barriers in emergency exits can boost evacuation rates

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London, Aug 25 (ANI): Putting an obstacle in emergency exits can make people evacuate a building more quickly, according to a study.

In the study, physicists timed a crowd of 50 women as they exited as fast as possible through a door, and then repeated the experiment with a 20-centimetre-wide pillar placed 65 centimetres in front of the exit to the left-hand side.

They found that the blockage improved the exit rate by an extra seven people per minute - from 2.8 people to 2.92 people per second, reports New Scientist.

Daichi Yanagisawa at the University of Tokyo, Japan, who led the research team, explained that the pillar creates a relatively uncrowded area where it's needed most - just in front of the exit.

Usually, the exit becomes clogged as people compete for the small space, which in turn slows the crowd.

Yanagisawa said that the pillar blocks pedestrians arriving at the exit from the left so effectively that the number of people attempting to occupy the space just in front of the exit is reduced.

And, thus, with reduced crowding, there are fewer conflicts and the outflow rate increases.

However, the researchers said that the positioning of the pillar is crucial-when they moved the pillar so that it stood directly in front of the exit's centre, rather than to the left, the outflow rate dropped to 2.78.

That happened because there was a second factor influencing outflow rate, dubbed the turning function.

As pedestrians approach the busy doorway they weave and duck to squeeze through the crowd. With every turn they lose momentum and their walking speed decreases, which reduces the rate of outflow through the exit.

But when the pillar is offset to the left, it increases the turning function of pedestrians approaching the exit from the left.

Although they take longer to reach the exit, the total effect is an increase in outflow rate since those approaching from the centre or the right have a comparatively free and empty route to the exit.

But if the pillar is central, it affects the turning function of most pedestrians approaching the exit.

And as more pedestrians are slowed down because of the obstacle, the total outflow rate drops.

The findings could be used to design better emergency exits, says Yanagisawa.

The study has been published in the journal Physical Review E. (ANI)

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