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Crowds and bottlenecks - move slowly to evacuate quickly



In crowd bottlenecks, the tendency is for individuals to panic and move quickly to get out of the squeezing crowd. Experiments with humans and sheep show that when a group has to move through a narrow opening, they take longer if each individual tries to move quickly (New Scientist, January 6, 2016). The advice is to move slowly to evacuate quickly through bottlenecks. In other words, individuals should move slowly in order for the group to escape quickly. While this was intuitive, it had not been scientifically tested before.

Bottlenecks are caused when a mass of people, animals, or objects are forced through a small opening (like the neck of a bottle).

Researcher Iker Zuriguel and colleagues at the University of Navarra in Spain conducted a series of three experiments to test evacuation through a narrow exit (such as a doorway or bottle neck), published in Physical Review E, doi.org/bbcq, on December 15, 2015.

In the first part of the experiment researchers enlisted the help of 95 volunteers for evacuation testing. The researchers put the volunteers in a room and asked them to perform three different types of evacuation procedures : (1) avoiding all physical contact, (2) allowing soft physical contact, and (3) allowing gentle pushing.

The results showed that more competition to evacuate meant a slower escape. Hence faster was not quicker – faster was slower. ‘People get stuck in the door,’ said Zuriguel, ‘which can be dangerous.’

The next part of the experiment was conducted with hungry sheep. ‘Sheep are useful,’ said Zuriguel, because they ‘are used to pushing each other just for food.’ Sheep move more quickly in warmer temperatures, so the researchers compared their speed through a doorway (the bottleneck) on warm and cool days.

The result of the sheep experiment was as expected – individual sheep moved more quickly when it was warm, but the flock as a whole was slower to get through the door.

A third experiment with objects showed the same effect. The faster-is-slower (FIS) effect was first predicted by computer simulations of pedestrians through a narrow exit. The third experiment used grains flowing out of a hopper over a vibrated incline.

Previous experiments had not allowed people to push each other. The University of Navarra findings suggest that FIS is a universal phenomenon for active matter passing through a narrow passage. Hence, for the design of emergency exits the FIS method should be reconsidered to – move slowly to evacuate quickly.

https://www.newscientist.com/article/mg22930552-200-dont-shove-sheep-and-humans-show-pushing-slows-evacuation/

Image: Philip Wallick/Corbis


MARTINA NICOLLS is the author of:- The Shortness of Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet (2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).
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