From Nature:
The annual pilgrimage of Muslims to Mecca in Saudi Arabia, known as the Hajj, has on occasion been marred by deaths from trampling in the huge crowds that gather for the rituals. But scientists studying how pedestrians move around think they have made such crowd disasters much less likely.
In 2006, 362 people died in the crush that developed in the town of Mina, where pilgrims gather to perform a ritual stoning of pillars representing the devil as part of the Hajj. This year’s ritual, which happened in late December and early January, went off without incident. Although there have been plenty of other accident-free years, this time the reason owes more to sound planning than to luck, says Dirk Helbing of the Dresden University of Technology in Germany. Hebling and his coworkers used the science of crowd dynamics to introduce a raft of new crowd-control measures.
“This Hajj, in contrast to many previous ones, was very safe, without any panics or incidents, even though it was expected to be the most critical ever and there were about 800,000 more pilgrims than the expected 3 million,” he says. “This great success was due to a completely different organization of pilgrim flows.”
More here.