31–40 of 43 posts
Earlier quoted context omitted.
How is clumping indicative of bad driving?
Left lanes are for passing. If you are in the left lane and not passing, guess what.
Crowds of a high enough density push people in orbital waves, with both clockwise and counterclockwise oscillations pulsing at 18 second intervals through the crowd. Monitoring these motions in realtime is possible and may help prevent crowd crush events. Also: At high densities crowds act like sticky springs, with the ground adding the sticky. 18 seconds before the next wave of people crushes you. 18 seconds to get…
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)
Earlier quoted context omitted.
Two things that would deserve clarification (although outside of the scope of the research here) are: (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..
A naive application of fluid dynamics would suggest that the answer to 2 is to go perpendicular to the flow until you reach a wall, then go against the flow towards an exit. 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…
Hypothetically, how would the dynamic change if it were a crowd of cats instead?
Earlier quoted context omitted.
A naive application of fluid dynamics would suggest that the answer to 2 is to go perpendicular to the flow until you reach a wall, then go against the flow towards an exit. 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…
> Human crowds have very fluid-like behavior, but of course they don't behave perfectly like a liquid in a pipe Hypothetically, how would the dynamic change if it were a crowd of cats instead?
Crowds of a high enough density push people in orbital waves, with both clockwise and counterclockwise oscillations pulsing at 18 second intervals through the crowd. Monitoring these motions in realtime is possible and may help prevent crowd crush events. Also: At high densities crowds act like sticky springs, with the ground adding the sticky. 18 seconds before the next wave of people crushes you. 18 seconds to get…
Earlier quoted context omitted.
How is clumping indicative of bad driving?
Unnecessary clumps are bad. They make merging and passing harder, desensitize you to nearby cars' presence, cause night vision problems, etc. 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 real…
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.
Nature is short-sighted Nature is governed by differential equations/local behaviour
Crowds of a high enough density push people in orbital waves, with both clockwise and counterclockwise oscillations pulsing at 18 second intervals through the crowd. Monitoring these motions in realtime is possible and may help prevent crowd crush events. Also: At high densities crowds act like sticky springs, with the ground adding the sticky. 18 seconds before the next wave of people crushes you. 18 seconds to get…
> 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.
Earlier quoted context omitted.
Two things that would deserve clarification (although outside of the scope of the research here) are: (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..
A naive application of fluid dynamics would suggest that the answer to 2 is to go perpendicular to the flow until you reach a wall, then go against the flow towards an exit. 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…
(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.)
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.