Here is a post talking about the World Health Organization putting together a body of evidence that cities that invest in active transportation maintain healthier citizenry.

Every year, 1.2 million people die in traffic crashes each year. And physical inactivity is responsible for 3.2 million deaths and 19 million healthy life years lost annually.

Dr. Carlos Dora continues to describe the problem:

Contrary to popular belief, more road space actually leads to more congestion, not less. This creates a “vicious cycle,” Dora said. He gives the example of parents who fear that their children will be hurt on their walk to school, so they drive them by car, instead, but this makes congestion even worse, and children become even more physically inactive and obese, thereby exacerbating the public health problem.

via Transport and Health: Measuring the Link | TheCityFix.com.