Crowd control

September 11, 2001. In the Twin Towers of New York City’s World Trade Center, intense fires are burning in and above the impact zones struck by hijacked airliners. People evacuating from the 110-story towers realize they are in danger, but they are not in a blind panic. They are not screaming and trampling one another. As they descend the densely packed stairwells, they are waiting in line, taking turns and assisting those who need help. A few office workers hold doors open and direct traffic. Thanks to the orderly evacuation and unofficial rescue efforts, the vast majority of people below the impact zones get out of the buildings alive.