21 people died and at least 652 were in part seriously harmed.
18 seconds before the next wave of people crushes you. 18 seconds to get out. 18 seconds could save your life.
> To address the role of confinement, we perform an additional series of measurements after the festival opening, when a security team splits the crowd into two halves (Fig. 3e and Supplementary Video 4). We find that the two decoupled crowds still oscillate but at a higher frequency. We measure the shortest dimension of the crowds before and after the festival opening, and the extent of the region of space where the 2010 Love Parade crowd featured chiral oscillations (Methods). Figure 3h shows that the velocity spectra of these markedly different crowds peak at the same value when rescaling the frequency w by the inverse of the confinement length L. This result strongly suggests that the period of the emergent oscillations depends on confinement, and is not an intrinsic 'material' property.
(1) When is it time to leave? At what threshold? Is it around an arm's length of free space between people?
And (2) Where to go? Straight line towards an exit? Perpendicular to the crowd? Exactly against the flow? Along the flow but towards edges? Probably depends on a lot of parameters..
In the middle of a crowd/fluid your motion is determined by the humans/molecules around you. The closer you get to a wall, the fewer particles have an influence on you. Just make sure it's not a wall people are moving towards.
Not sure if anyone has studied how well this holds up to humans. Human crowds have very fluid-like behavior, but of course they don't behave perfectly like a liquid in a pipe
Maybe giant inflated or crushable areas around an exit that could take up slack?
maybe tie the crush event with something else, like opening extra doors, turning on lighted warning signs or illuminating exits?
Meaning that, if you notice the frequency by which people shift their weight and move -- its likely in that window, assuming other externalities (bathroom, heat, thirst, anger, etc -- the physiological cycle of body comfort may be in that area of 18 secs)
If this interests you, some prior context on “crowd crush” might too. John Seabrook, writing in the New Yorker in 2011 (in response to the “Black Friday” crushing deaths at US Wal-Marts), engagingly profiled examples from the past few decades of this category of disaster (in the US and Europe). Along the way he traces a few shifts in thinking about such crowd behavior, from “mob psychology” to Paul Wertheimer‘s colorful observational studies to Dirk Helbing’s fluid-dynamical modeling.
Precision and emergence in the physics of life with William Bialek
Nature is short-sighted <=> Nature is governed by differential equations/local behaviour
Just to add, this paper has nice figures generally!
What I see every time I drive it is a new clumping behavior that emerges: some big rigs tend to drive quite slow but do that thing where they want to pass someone going 54 and they are going 55 so it takes ages and the traffic in the left lane gets longer and longer, leaving a gap in the right lane.
At thing point, some drivers say "fuck it" and zip down the right lane and aggressively merge back in to shorten their wait getting around the blockage. As you are likely driving this route for hours (SF to LA) you see it happen more and more often and it becomes more and more prevalent. I find it exhausting because there is no way to veg the whole drive unless you are the slowest car out there because at best someone is going to jab in front of you at the last second and you have to mash you brakes to avoid them.
The interesting thing is that this is always how the traffic flows on this road, and nowhere else. It must be a precise combination of traffic levels, lanes available, traffic mix, differring speeds and even average distance travelling, so people notice and feel compelled to respond to the pattern.
I think the specific pattern you're talking about happens because when a truck is passing slowly but infrequently, it makes some sense to be polite and line up behind it. When trucks are passing so frequently, and so incredibly slowly, being polite is useless. There needs to be a zipper merge happening behind the truck being passed. But the left lane people feel they've paid their dues by waiting in line, and half the right lane people don't even care. The right lane people also stay so close to the truck in front that they can't safely merge left at highway speeds anyway. People also tend to not fill back in to the right lane between truck passes. I'm not sure that would even help, but it does make people who do seem like cheaters to the people who refuse to.
(edit: “crowd crush safety expert” Paul Wertheimer, who came to some notoriety through studying mosh pits from within them, apparently suggests—at least in situations where the crowd is moving toward a clear focal point—you’re right: he recommends the edges
https://www.cnn.com/2021/11/13/us/how-to-stay-safe-at-concer...
That said I note that the authors of TFA draw a distinction between dense-crowd situations undergoing unidirectional flow and the steady, confined dense crowd whose behavior they describe.)
Hypothetically, how would the dynamic change if it were a crowd of cats instead?
A good driver will first notice they are in an unnecessary clump, and a bad driver probably won't.
A good driver will try to minimize the the time they spend relatively motionless to other cars (other than behind them at a safe follow distance). A bad driver either doesn't realize as in the previous point, doesn't care, or actually prefers it as some kind of crutch. Sometimes the leader of the clump ends up that way because they will speed up whenever those behind them try to pass. Sometimes the rear of the pack is a driving zombie who will close any distance between them and the car in front, but will never choose to pass. And so on...
The tall vehicle behind the Tesla will hide the fact that the slow Tesla on the left lane is slow for no reason, people behind the tall vehicle will think there is traffic. And we will all go 55 on the left lane, thinking there is traffic. Until some incline allows people to see that there is no real traffic and then the Tesla gets overtaken and clump is broken.