Every year, the amount of time Americans spend walking declines. Driving, on the other hand, has slightly but steadily risen in popularity since 2008. During that period, the number of pedestrians killed by people in cars has skyrocketed.

Investigating this disturbing trend is the subject of a report put out by the National Complete Streets Coalition (a program under Smart Growth America) called Dangerous by Design. The coalition releases this report annually, says Emiko Atherton, the coalition director, but what's striking is that "things are just getting worse," she says. "When you look at the numbers, four of the five major metro areas in the U.S. are just growing more dangerous for pedestrians."

Since 2008, the number of people struck and killed by a driver while walking rose by 35%, to 49,340 people in a year. The report authors note that this is the equivalent of a jumbo jet full of people dying each day.