Friday, August 21, 2009

For a Quick Exit, Just Block the Fire Door



Most fire codes require that the pathway to an emergency exit be kept wide open, but according to researchers in Japan, placing an obstruction next to an exit may actually help crowds of people to get out of a room more efficiently.

Researchers found that when people bottleneck near an exit, they start to jostle each other for position. The jostling acts much like friction, slowing down the rate at which people can exit. Introducing a strategically-placed obstacle near the exit can reduce the number of people pushing for the exit, speeding up the rate at which people can pass through.

"We found that we can evacuate faster if we put an obstacle at the suitable position in front of the exit," said Daichi Yanagisawa, who lead the study from the University of Tokyo in Japan.

The researchers started their study by having large simulated crowds of people bottleneck around small exits, and then introduced obstacles that everyone would have to avoid in order to reach the exit. Most of the time, the obstacles reduced the number of people able to exit per minute. Surprisingly, they found more people could escape in less time if an obstacle was placed about 30 degrees to either the right or left side of an exit door.

"Contrary to our intuition, the obstruction by the obstacle increases the pedestrian outflow in a certain case, since it decreases conflicts among pedestrians," Yanagisawa said.

Researchers found that having an inanimate pole take up the space of a person reduced the number of time-consuming conflicts between people near the exit. Similarly, the pole's placement slightly off to one side of the doorway reduced the time it took for a person coming from the other direction to turn toward the exit.

To test their results, the researchers went to the studio of a local TV station and watched 50 volunteers exit through a narrow door. They found that the crowd of real people closely mirrored the researcher's previous computer predictions. Likewise, when they placed a pole to one side of the exit, the people were able to exit faster than when there was no obstruction at all.

Yanagisawa's team was the first to put this into mathematical terms.

"I believe that our work will help design better and more efficient fire escapes since our model gives us the value of pedestrian outflows based on both theoretical and experimental study," Yanagisawa said.

During the experiment, the team also found that people exiting in a single-file line were by far the most efficient. Yanagisawa said that the next step is to program models of people intelligent enough to self-organize into a line.

Mike Lucibella
Inside Science News Service



Research to appear in the journal Physical Review E

18 comments:

  1. This is like the games where you throw the balls from the top and they start moving left/right when hitting obstacles giving time for few balls to exit through the bottom. If you throw all the balls without obstacles they would block the exit at the bottom.

    I hope this research gets more popular and applied on each emergency door.

    Nice.

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  2. fire exits and drills are a special case because people make an honest effort to exit, rather than simply enjoying their day and wandering where they please. Is there a way to use obstructions to speed up diabetic gawkers and confused, unmotivated tourists that stall at the tops of staircases? After you solve that maybe you could model people intelligent enough to think of the 200 people on the same train car behind them.

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  3. I wonder if this same logic can get applied to car traffic to help reduce traffic conjestion around exits? Traffic still suffers from the "unmotivated tourist" (or the lost tourist), but it's certainly noticable around construction areas where everyone has but one option... Very interesting article!

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  4. I am surprized this was not expected. You see the exact same result when a lane on the freeway is closed. If it is easy for drivers to drive all the way to the choke point before merging, they slow down traffic right at the choke point. If they are forced to merge farther away from the choke point, everyone can get up to speed through the narrow part of the freeway.

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  6. Actually after reading a book called "Traffic" the most efficient way to use a highway is to drive all the way up to the choke point. Studies were done, and more cars pass per hour if all lanes are used to the maximum extent.

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  7. > Is there a way to use obstructions to speed up diabetic gawkers and confused, unmotivated tourists that stall at the tops of staircases?

    Sure. Start a fire.

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  8. how many people would be saying "oh, seriously?!" if the conclusion was that an obstacle actually decreases the time in which people escapes?

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  9. This worked in Japan because they know Pachinko. Try this in the US.

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  10. This isn't new: University of Greenwich UK showed similar results at least 10 years ago.

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  11. I'm pretty sure I read an article on the same topic - with the same conclusion - while I was in highschool.
    That's 20 years ago ...

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  12. Very little is completely new in science. It's a progressive discipline, with most research building on previous work. In fact, I would be extra cautious about believing any truly unprecidented discovery or advance.

    I'm sure similar studies to this one have been done many times. I'd have to read the paper, and the previous work cited at the end of the paper, to understand what's different about this experiment. Regardless, it's an interesting bit of science because it makes you question the common wisdom of designing emergency exits. Anything that makes you think is good, IMHO.

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  13. This experiment may have been done before, but, as the article reports: "Yanagisawa's team was the first to put it in mathematical terms."

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  14. I remember these things being discussed 20 years ago when virtual reality was a hot buzzword in the media. Fire safety researchers were using VR then as a tool to watch in human terms the mathematical models of the day, they too found that certain obstacles could be designed in so people go through faster - it had to do with cutting down the number of people you had to think about in the crush, divide the crush up into two or three streams and people go through that more quickly.

    The way this new research is reported suggests it's more like water flowing through a hose - constrict the end of the hose and the water, which has to flow through at the same volume rate, comes out quicker but that doesn't deal with the psychology of crowds. Need to read the paper itself and try and ignore the journalistic soundbites.

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  15. I saw nothing in the study that added a full panic element to the excercise. What if the room were on fire and the people were exiting for thier very lives. You can not simulate that fight or flight. I wonder if the results would be the same.

    FF

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  16. This interesting blog made it on our "Building Code Discussions Group" (BCDG) where 1000's worldwide come together to interact regarding building, fire and related topics!
    http://bcodes.infopop.cc/eve/forums/a/tpc/f/804093073/m/372101613

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  17. "I saw nothing in the study that added a full panic element to the excercise. What if the room were on fire and the people were exiting for thier very lives. You can not simulate that fight or flight. I wonder if the results would be the same."

    If you set every object's only goal to exit...
    You might increase their "desire" to exit, which may mean increasing the amount they will push other particles out of the way to get to the exit. This may serve to increase "friction", making overall exit slower. However the addition of the pole should make it quicker to exit than if there were no pole, regardless of the amount of panic.

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  18. Would this idea be problematic for wheelchair users?

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