the subject here went off from the main OP's subject but I actually found it a wonderful info and discussion here. On top of that 80% that's living in urban areas most of the cities in the states are not that bicycle friendly and have alot of cycling infrastructure like Portland and New York has been increasing bike lanes all over town. The cities actually have to make an effort to show that cycling is safe before you get the majority to even think of hopping on a bike to work. I'm betting alot of people don't actually like sharing lanes with a car in busy downtown traffic and feel uncomfortable about it. When I rode with some friends all the way downtown they found it a bit of a rush and scary when riding and keeping up with the mess in the downtown core areas. I found it fun as hell cause they're all gridlocked but me!