Taking the panic out of a stampede

Scientists from Hungary and Germany believe they can use the laws of physics in a computer simulation to predict and prevent crowd panic.

When crowds of people stampede, such as ten years ago when more than 1,400 pilgrims were killed inside a tunnel leading to Mecca, they are usually explained in terms of psychology.

The computer models from the Institute for Economics and Traffic at Dresden University of Technology rely on distances, sizes and velocities instead of emotional states. The results, however, are simulations that are similar to the panic caused in a stampede of humans.

The computer models reflect the conditions of a room from which people are trying to escape but cannot use or see exits. The virtual victims appear as particles that replicate an average person’s speed, size and ideal distance from others.

Under most circumstances, a crowd exits a venue in a controlled manner because everyone is moving at a leisurely pace and at an adequate distance from one another, the researchers said.

But when the speed of the individuals increases in a panic, they bump into each other, creating friction and violation of personal space. Consequently, almost everybody moves less quickly.

Eventually, solid arch-shaped barriers of people clump around the exits and even fewer people can pass to safety. Victims collapse and are trampled, creating further obstacles for the others.

“People want to leave faster, but the result is that they are leaving slower and then the tragedy begins,” said Dirk Helbing, a professor at the Institute for Economics and Traffic at Dresden University of Technology.

One solution, said the researchers, is to build a partial barrier in front of the exit that would absorb the sort of pressure exerted by a crowd in panic situations.

The researchers also used their simulation to devise strategies for surviving crowd panic. In the case of a burning theatre where smoke obscures the exits, just acting alone or following others can be deadly, they said.

The new computer models are especially useful because they consider individual actions within the group, said David J. Low, a civil engineer at Heriot-Watt University.

Most modern buildings are designed assuming crowd flow through exits like fluid through a pipe, said Low.’This traditional approach assumes that the crowd is made up of identical, unthinking elements,’ he said. ‘A fluid particle cannot experience fear or pain, cannot have a preferred motion, cannot make decisions and cannot stumble and fall.’