[HN Gopher] Emergence of collective oscillations in human crowds
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Emergence of collective oscillations in human crowds
Author : shalg
Score : 82 points
Date : 2025-02-09 01:20 UTC (21 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| nacho-daddy wrote:
| 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 out. 18 seconds could save your life.
| trimethylpurine wrote:
| I like your summary. Thanks!
| diegoperini wrote:
| Beautiful. Thank you.
| cmehdy wrote:
| 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..
| vxxzy wrote:
| I don't recall where, but for some reason I remember learning
| that if people start to bump into you too many times, that's
| a warning shot to get out. It was something like "bumps per
| second".
| wongarsu wrote:
| 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 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
| xeonmc wrote:
| > 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?
| thfuran wrote:
| Non-cat fluids don't usually spontaneously draw knives
| and start cutting themselves apart.
| alwa wrote:
| Is there anything to the notion that you might prefer to be
| batted around in the "soft body" portion of the dense-crowd
| "fluid" rather than pinned between several tons of soft
| bodies in motion and a hard limit? You seem rather more
| crushable than an individual molecule might be...
|
| (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.)
| metalman wrote:
| .,.......except at a Greatfull Dead concert where this
| phenominon is called the "seeing the gears" or "have you seen
| the gears" nobody gets crushed, everybody gets....where they
| need to be plus up in the stands, are human waves of people,
| who are also bouncing a multitude of beach balls around, some
| of which are giant, some of which are not filled with air
| everybody steping to the groove.....except the spinners, who
| are another phenominon, the tapers huddled, but looking for any
| likely person at all to spell them bobby just played the
| grammys......
| patcon wrote:
| Of note: If that 18 second rule became known to a significant
| number of people, the dynamic will change
| alwa wrote:
| I read it kind of quickly, but didn't their analysis suggest
| that the 18s period in question may have been specific to the
| Plaza Consistorial--that is, that the specific oscillation
| period may depend on the size (and possibly shape) of the
| confinement area?
|
| > _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._
| qwertox wrote:
| The article contains a link to a YouTube video of the Loveparade
| 2010. It's pretty long and only at the end the oscillations are
| very noticeable (18:33 [0]).
|
| 21 people died and at least 652 were in part seriously harmed.
|
| [0] https://youtu.be/QpzISdBE3dA?t=1113
| kanavs wrote:
| Interesting work! It is interesting how a lot of the models in
| physics and outside of it comes down to variations of harmonic
| oscillators (in this case macroscopic chiral oscillators). I am
| curious is the chirality gets imposed by the location and the
| architecture. Another interesting bit to explore would be how the
| agency (in my head agency is loosely defined as the number of
| possible actions you can take) of each individual gets contained
| as the crowd gets dense. If there is a way to define agency
| mathematically, it would be interesting to look at the
| correlation between agency and crowd density (my guess is inverse
| correlation) and then come up with strategies to increase the
| agency.
| silver911r wrote:
| I noticed a similar phenomenon while driving on the highway.
| Vehicles on the other side of the road seem to group up and
| travel in clusters. Like traffic naturally oscillates into these
| packets?
| jampekka wrote:
| This is a well known phenomenon in traffic engineering and can
| be modeled with e.g. fluid dynamics.
|
| https://en.m.wikipedia.org/wiki/Traffic_wave
| silver911r wrote:
| I had heard of traffic waves in congestion, but this
| phenomenon happens on open roads. I often notice vehicles
| forming packets when there isn't traffic. Like natural
| clustering? If I drive the speed limit, cars will start to
| bunch up behind me, even when there is an open lane. Then, a
| driver will speed up in the passing lane, but when they reach
| me, they often slow down slightly or a lot and ride next to
| me without passing.
| jwlit wrote:
| There's a good site all about that: http://trafficwaves.org/
| jrootabega wrote:
| The traffic waves mentioned in the other replies are not the
| same as clumping. People clump up while driving, even on the
| emptiest of highways, because they are bad drivers. This was
| happening long before automatic braking, but that has made it
| more common.
| taurknaut wrote:
| How is clumping indicative of bad driving?
| jrootabega wrote:
| 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
| 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...
| greentxt wrote:
| Stay in the far right lane unless passing. Don't
| tailgate. Those 2 rules would solve a lot of problems if
| they were enforced. Instead, there is heavy enforcement
| of the speed limit, which in and of itself isn't a safety
| concern.
| therein wrote:
| In the Bay area, what I noticed is, unnecessary clumps
| almost always get nucleated by a Tesla going lower than
| the speed limit on the left lane and then a tall vehicle
| behind them.
|
| 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.
| tristor wrote:
| Because it indicates that they are not driving to the
| conditions of the road and being attentive.
| greentxt wrote:
| Left lanes are for passing. If you are in the left lane and
| not passing, guess what.
| jrootabega wrote:
| I agree that clumps usually end up blocking passing
| lanes, but they're also bad when in any lane(s).
| greentxt wrote:
| A clump == blocking the passing lane. They are
| definitionally the same.
| taurknaut wrote:
| I think about a large cluster of cars, say 6-12 cars,
| going roughly the same speed. Nothing about that entails
| blocking multiple lanes, certainly not densely enough to
| preclude someone from passing.
| pglevy wrote:
| Guess what... Sometimes I need to take a left exit. And
| there will frequently be a bunch of clumping chumps doing
| 20 over in the left lane. So I get over when I can.
| lubujackson wrote:
| There is very specific clumping behavior on the I5 in Northern
| California I've noticed. It is a long, 2 lane highway often
| used by truckers. It tends to be fairly congested but not ever
| backed up.
|
| 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.
| jrootabega wrote:
| In my experience, anywhere there is heavy semi truck traffic
| will have significant problems once there are enough cars
| around ("enough" being far less than it should be). 2 lanes,
| 3 lanes, 4 lanes, hills, it's all bad. But yeah, only 2 lanes
| per direction makes it comically awful. Happens on sections
| of I-81 too.
|
| 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.
| nthingtohide wrote:
| I recommend William Bialek's lectures who deep dives into how
| maths can be applied to messy macro-world of biology, neurons,
| cells, birds, so on and so forth.
|
| Precision and emergence in the physics of life with William
| Bialek
|
| https://www.youtube.com/watch?v=c1hd5El2gqc
| fecal_henge wrote:
| Why are they showing power spectra with +- frequencies?Beyond
| looking pretty it is wasteful of figure real estate.
|
| Just to add, this paper has nice figures generally!
| deadbabe wrote:
| Most dangerous crowd I've been in was in 2021 at Astroworld,
| several people died from being crushed, it felt like there was no
| escape.
| paulorlando wrote:
| I used to have a view from about 3 stories up of one of the
| densest crosswalks in Hong Kong. As the crowd of people crossed
| the street in two directions, they would organize into 7 rivers
| of flow (3 one way, 4 in the other). The rivers were surprisingly
| consistent over the months I watched this.
| xeonmc wrote:
| All systems with finite speed of information propagation will
| produce oscillatory phenomena emergently.
|
| Nature is short-sighted <=> Nature is governed by differential
| equations/local behaviour
| TeMPOraL wrote:
| Now I wonder if there's some insight to be gained from looking
| at the crowd behavior in the frequency domain, i.e. through a
| Fourier transform?
| alwa wrote:
| What cool work! I wish I had this transformative sensation more
| often: of the quick, clear shift in my thinking after someone's
| careful study of a familiar problem results in convincing models
| simple enough for a non-expert to wrap their mind around.
|
| 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.
|
| https://www.newyorker.com/magazine/2011/02/07/crush-point
|
| https://archive.is/b1Flz
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