Look both ways before you cross the street. Especially in places such as Atlanta, Miami, and Tampa - three of the ten most dangerous cities for pedestrians, according to a recent study by the Surface Transportation Policy Project. Walking is 36 times more dangerous than driving. In 59 percent of cases, pedestrians are killed while trying to cross in the middle of the street because they couldn't find a crosswalk. Lack of crosswalks is just one factor that makes these city streets so mean. Others include too few sidewalks, and wide streets that allow cars to travel at high speeds. The study also found that this disinclination to walk is contributing to Americans' health problems. Over the past 20 years, the number of pedestrians has dropped by 42 percent, while the number of overweight Americans has grown by 40 percent. Perhaps they find the couch a safer alternative.