The virtual victims appear as particles that reflect an average person's speed, size and desired distance from others. Under normal circumstances, a crowd exits a theater or stadium in an orderly and coordinated fashion 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 violating personal space. As a result, 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.
One solution is to build a partial barrier in front of the exit, the researchers said. It could absorb pressure from the crowd that can become strong enough to crush a person, break a brick wall or bend steel. As the world becomes more crowded, such simulations will grow more important for architects, event planners and police. This year, eight people were killed in July at a rock festival near Copenhagen, and a dozen died the same month after a World Cup match in Zimbabwe. Ten years ago, more than 1,400 pilgrims were killed inside a tunnel leading to Mecca.