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.
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.
"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.
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?
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.
That's not really a great description of what's happening. The group in-front of the exit is moving vary slowly and everyone needs to accelerate before the exit. By limiting things to two lines people are moving faster as they approach the point of maximum contention so they don't need to accelerate as much. On top of this you add delays as people content left right or center at the exit.
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.
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.
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)
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.
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.
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.
