Researchers say the concept of “sidewalk rage” is real. One scientist has even developed a Pedestrian Aggressiveness Syndrome Scale to map out how people express their fury. At its most extreme, sidewalk rage can signal a psychiatric condition known as “intermittent explosive disorder,” researchers say. On Facebook, there’s a group called “I Secretly Want to Punch Slow Walking People in the Back of the Head” that boasts nearly 15,000 members…

Signs of a sidewalk rager include muttering or bumping into others; uncaringly hogging a walking lane; and acting in a hostile manner by staring, giving a “mean face” or approaching others too closely, says Leon James, a psychology professor at the University of Hawaii who studies pedestrian and driver aggression.