We probably already knew this, but in case we didn't: The American Heart Association says "the simplest, positive change you can make to effectively improve your heart health is to start walking." For starters, they suggest exercising 150 minutes a week.
For the US.... Per this recent report's charts/data...Fort Worth is one of the most dangerous cities for pedestrians and bicyclists. Austin faired much better! Boston proved to be the safest for both according to their metrics.
Visit the results here.