Americans walk less than the citizens of any other industrialized nation, says Tom Vanderbilt. In this file photo from last summer, pedestrians and a cyclist cross the Brooklyn Bridge in New York City. Chip Somodevilla/Getty Images hide caption

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According to the Pedestrian Aggressiveness Syndrome Scale, if you find yourself "feeling stress and impatience when walking in a crowded area," you may have sidewalk rage. sculpies/iStockphoto hide caption

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