The Science, and Art, of Navigating a Crowded Sidewalk

If you've ever tried to navigate the sidewalks of SoHo on a busy weekend, it may seem like the maddening pedestrian behavior is chaotic and irrational. To the contrary, however, humans behave like other animals in crowds, according to a natural logic. And the science of pedestrian movement can help explain how the sidewalk animals are behaving. With the help of Fred Kent, from the Project for Public Spaces, who learned his craft from the eminent urban sociologist William H. Whyte, Horowitz describes the three primary rules that guide pedestrian movement.

"First, avoid bumping into others (while staying comfortably close)... A second rule: Follow whoever is in front of you... The final rule: Keep up with those next to you," explains Horowitz.

"These rules of 'attraction' (staying with others ...), 'avoidance' ( ...while not too close), and 'alignment' (going the same direction and speed as those around you) are sufficient to explain all herd, school, flock and swarm behavior — not to mention that of big-brained and busy human pedestrians."