Why Crowds Can Turn Deadly

A crowd in motion is a pretty remarkable thing. Pedestrians walking down a sidewalk in opposite directions usually manage not to bump into each other. Same for people sharing a crosswalk from opposite corners of an intersection. At a larger event, people will often form what look like neat traffic lanes moving through a static crowd when, say, the port-o-potties are on one end of a festival and the beer stand is on the other. Or think of a time when you’ve tried to cross the concourse to get to the bathroom at a baseball game when everyone else is streaming for the exits. Frogger-like, most of will us move diagonally through the flow of fans such that no one has to stop and no one collides.

All of these patterns are subtle signs that pedestrians in motion behave an awful lot like fluid.