Cell phone cameras reveal how people got crushed in a crowd

crowdby James Cridland

The physics of crowds can kill
[Via Boing Boing]

Almost two years ago, 21 people died when they were crushed to death in the crowd at the Love Parade music festival in Germany. Now, scientists have been able to pinpoint exactly what lead to those deaths. Here’s a hint: It wasn’t a stampede, there’s no evidence of intentional pushing, and it doesn’t look like mass hysteria had anything to do with the deaths. So how did those 21 people die? Physics. (Via Jennifer Ouellette)

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This is probable the fist major crowd disaster where all the tools of social media were brought to bear to get video, use GPS, get timestamps, use Google Earth to pinpoint the video locations, etc. Almost all of the data was crowdsourced and produced by volunteers.

The researchers were able to examine YouTube videos of the disaster with geolocation of where they were taken. (You can see this and watch the linked videos, although some of them are quite harrowing.)

The people were not crushed by stampede or mass movement. There was no mass pushing or movement towards alternate exists. They were killed by a crowd quake, a very different phenomenon than panic running.

They appear to have been at a pressure point of the location – a right angle turn – where the waves of movement tended to push the people closer and closer together.

At a critical point a large number of them became ‘jammed’ with little to no room between them. At this point, any shock to the system was transmitted throughout the system, just like it was one big block of people. You can see the shockwaves rippling through these groups in some videos, even while other people just meters away are not moving at all.

And this jam persisted, even when there was lots of empty space perhaps 10 meters away (this video shows the area where most of the deaths occurred) . In some of the videos, you can see people in the open spaces having to physically pull people away from the jam – it could not unjam itself. Even 10 minutes later, with most of the area cleared and rescue vehicles appearing, there is still a large clump of people unsuccessfully trying to unjam.

And the change from laughing with friends to fearful for one’s life happens very quickly.

It is obvious that a mass stampede is not what created this. It is almost like a phase shift that happens with non-Newtonian Fluids showing rheopecty features – they start as a liquid but when put under stress become more and more solid.

I’ve been in situations like this. Places so close together that the entire group could only move as one, without any of us doing anything but trying to stay upright. The lucky thing was that the mass was not near a wall and was able to move as one though open space and thus dissipate. But these poor people ran into an unyielding wall.

It appears that often in these large crowds semi-solid masses of people can lock together and become very hard to unlock. Forces that his this mass are transmitted through it in ways that can very hazardous to the people in the masses. One thing this analysis may show if how to predict better how this mass might form and how to most rapidly dissipate it.

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