In a big crowd, as at the hajj, danger can come on quickly
By MALCOLM RITTER

NEW YORK (AP) — When too many people are squeezed into too small a space, the situation can turn dangerous very quickly, experts say. And that, they say, may be key to understanding the deaths of more than 700 pilgrims on the outskirts of Mecca.

"It's largely a physical phenomenon, not a psychological one," says Dirk Helbing, a professor of computational social science at ETH Zurich, who has studied crowds and disasters.

When the density is too high, movements of a body "transfers forces to other bodies. These forces can add up and create uncontrollable movements in the crowd," he said Thursday.

"As a result ... people might fall on the ground and might be trampled by others" or die of suffocation as others fall on top of them, he said.

And it can happen fast. Even a small incident like two people starting a fight or trying to walk against the crowd can quickly snarl a free-flowing crowd in large-scale congestion, he said. As more and more people pour in, the density builds up, setting the stage for lethal turbulence.

So "a small problem turns into a big problem that is not controllable anymore," Helbing said. A large crowd can "get out of control very quickly."

Even for those who stay on their feet, the pressure of the surrounding bodies builds up "and people can't breathe," said Keith Still, a professor of crowd science at Manchester Metropolitan University in England.

"People don't die because they panic. They panic because they are dying."

Still, who has worked on hajj crowd management with security officials in the past but had no direct knowledge of this year's situation, said Thursday's disaster in Saudi Arabia appeared to result from too many people jammed into a space too small to hold them.

"Every system has a finite limit, the number of people who can go through it," Still said. "When you get above that number, the risks increase exponentially."

At the hajj, he said, "it just looks like the system has gone beyond its safe capacity."

The Saudi Interior Ministry has said the crush appeared to result from two waves of Muslim pilgrims meeting at an intersection. King Salman has pledged a speedy investigation to improve crowd management.

One effective strategy for crowd safety, Still said, is a hold-and-release approach. People are stopped temporarily from following a route and then let go in pulses. "That creates space," Still said.

Helbing said the hajj is "one of the most difficult mass events to organize," in part because some pilgrims aren't registered for the event and so don't adhere to assigned camps or official schedules, and the hajj attracts people of many origins and languages.

The last such hajj incident was nine years ago near the same site.

"When such an event has been safe for a number of years, that's not a reason to relax and take things easy," he said. "There is always a kind of a critical threshold. If your system happens to get beyond that threshold, then things get uncontrollable."


-- (c) Associated Press 2015-09-25

Why worry? was it not the will of allah?

I was told that if you die during Ramadan, you automatically go to heaven. Is the same true of those at the Haj?

they can finally make some place for refugees, right ?

So many sick Muslim haters posted stupid comment over people's death. Hope they get the same sort of death with in their loved ones only then they will realize that Any death is sad.

quite often a single posting is sufficient to recognise the character of a poster

they can finally make some place for refugees, right ?

Far be it from me to normally spring to the defense of the Saudis, but I believe from more than one source that they have been a victim of what is best described as "Yellow journalism". According to this article the Saudis are actually educating 100,000 Syrian children in their schools. This would extrapolate to the total number of Syrians there being greater. What their long term status is I know not but in the interests of fairness I thought I'd better share this.

http://www.huffingtonpost.com/anhvinh-doanvo/europes-crisis-refugees_b_8175924.html

However, a look at Saudi Arabia's UNHCR page has a few curious footnotes that Western publications are conveniently omitting. The UNHCR counts refugees by noting only those "persons recognized as refugees under the 1951 UN Convention/1967 Protocol, the 1969 OAU Convention, in accordance with the UNHCR Statute, persons granted a complementary form of protection and those granted temporary protection." Saudi Arabia, Kuwait, Qatar, and the UAE are not parties to any of the UN protocols on refugees, and so through this technicality, they, along with most of their refugees, are excluded from many refugee counting mechanisms.

Edited September 25, 201510 yr by Steely Dan

quite often a single posting is sufficient to recognise the character of a poster

So very true ...

Guess my friend should never have screamed out that there were free bacon sarmies at this side of the intersection?

Those chaps just loooove bacon.

Unbelievably sick post from a troll removed.