EcoWatch: Have you noticed more two-wheelers on your commute, especially if you live in a city? According to the U.S. Census Bureau, the number of Americans who travel to work by bike increased an incredible 60 percent over the last decade, making it the largest percentage increase of all commuting modes. People choose to bike for many reasons (it saves money, its good for health), but here are six big reasons more Americans are leaving the car keys at home: 1. Cities are wooing millenials. The Pew Charitable...