
Ants show that emergency exits can work better when they’re obstructed - leakybucket
http://nautil.us/issue/13/symmetry/want-to-get-out-alive-follow-the-ants
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Kenji
That's interesting. I once took a sociology class about the behaviour of
panicking crowds and we covered exactly this phenomenon, that is, if you put a
pillar in front of the emergency exit (without completely blocking it, of
course), panicking people can get out faster. It seems counterintuitive but
it's been shown numerous times.

~~~
mantrax5
It basically reduces deadlock chance.

When you have one exit and it's blocked due to many people attempting to fit
at once, the entire queue is congested.

That barrier turns one exit into two exits (even if it's backed by only one
real exit). If one is congested, people can still flow through the other one,
and vice versa.

This explains why the evacuation rate is roughly twice faster.

If the barrier is designed to even more virtual exits, it'll be even faster.

And there's an even faster way, that requires no architectural changes, but
people will have to be trained in it so well, that they'd follow it even in
panic.

And this would be some heuristic which orders people in an unambiguous way, so
only one person is attempting to exit at a given moment.

I don't know, left to right order, split in rows, people holding hands... Some
creative solution is required to decide what that heuristic would be.

Queues have no congestion, so they'll represent the fastest possible rate of
evacuation through a single exit.

~~~
greenyoda
_" And this would be some heuristic which orders people in an unambiguous way,
so only one person is attempting to exit at a given moment."_

Given how badly people behave at four-way stop signs (where there's an
unambiguous ordering algorithm that most drivers seem to ignore), I don't
think there's much hope for a heuristic ordering working well for panicked
crowds at emergency exits.

~~~
YokoZar
Are you sure it's unambiguous? Four way stops have both a "whoever was here
first goes" rule and a "we arrived at approximately the same time so the
person on the right goes" rule. That alone adds ambiguity, as they're not well
defined.

But it gets worse than that, as pedestrians have priority and can break up the
established order. If it's "my" turn, but a pedestrian blocks only my way,
someone else can rightly cross out of turn, but then once the pedestrian is
clear when does it become my turn again?

~~~
farmfood
I moved to the US four years ago from the UK, and I think four way stops are
wonderful. I've yet to experience the disorder suggested. I grip the wheel,
narrow my eyes and approach with extreme caution. I like think everyone else
does too.

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caio1982
I remember watching once a TV show (perhaps in the old days of Discovery
Channel) about experiments with obstacles put in front of elevators, so people
wouldn't clutter in front of it and IIRC they have found the same thing back
then. I wish I had magic skills to find a video of that show.

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brc
It would seem to me that the visual obstruction of the column causes as much
as the physical obstruction. An interesting twist on the experiement would be
to construct a clear obstruction that people could see through - and see if
that impeded the flow because of impatience at being nearly outside.

Also I wonder if a fake wall with 5 exit doors in it (close to each other),
that obscured the one _actual_ exist would speed up flow - presuming people
selecting the general area of the exit first, then the detail of the exit
point second. If there were 5 single doors it would separate the flow to the
actual choke point, but without producing the same type of barricade.

If this research turned out to be widely applicable, I wonder if placing
airline staff in front of a door would speed the exit of people through it?

I also suspect there is an optimum shape for the obstruction, and I expect
that it isn't round.

All interesting stuff.

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CaptainZapp
That's actually pretty much common knowledge with experts studying people
flows and emergency evacuations.

If you're interested in the subject The New Yorker has a fascinating read on
the subject (CRUSH POINT - When large crowds assemble, is there a way to keep
them safe? [2011]) which makes this argument. (Warning! It's long)

~~~
kahirsch
[http://www.newyorker.com/reporting/2011/02/07/110207fa_fact_...](http://www.newyorker.com/reporting/2011/02/07/110207fa_fact_seabrook?currentPage=all)

~~~
CaptainZapp
Thanks.

Hanging my head in shame for the omitted link.

Sorry for the oversight, since it's a really interesting read.

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andygates
Interesting application. The idea's not new: wasn't the central thingy in the
concourse in Grand Central Station found to have exactly this effect? Without
it, people dither and take longer to cross a clear space - paradoxical, but
that's science for you.

~~~
chinpokomon
Precisely what I was going to comment about. I think that leverages similar
principles although the application is slightly different.

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gjjhjjjhhh
Simulate the scenario with water in a pool with a tiny pipe opening at the
bottom if the pool leading down. The water will shoot out with a high velocity
this means the pressure in the pipe will be higher than pressure in the pool.
If you apply this analogy to people and exits, it means that the people
directly in the exit hallway( the pipe ) will experience a high change in
speed, and since people aren't fluid, friction, thus making their escape more
difficult.

~~~
skj
The pressure in the pipe is the same as the pressure in the pool.
Additionally, the meter^3/minute is the same in the pool in the pipe, but the
with the pipe, the meter^2 is much smaller. So, to keep the same rate of
fluid, the meter/minute (speed) has to be much higher.

~~~
billly
[http://en.wikipedia.org/wiki/Bernoulli's_principle](http://en.wikipedia.org/wiki/Bernoulli's_principle)
Where velocity increases, pressure decreases.

