They were both more prevalent, and presumably, more popular at the Democratic National Convention than they have been this week at the RNC, but that's not their fault. "They" refers to the hundreds of green bikes that have been shipped from across the country by Freewheelin', a non-profit bike sharing organization based in Louisville, Kentucky that collaborated with Humana, a health services company, and Bikes Belong, a biking advocacy group, to set up shop in both Denver and St. Paul for the political conventions in those cities. As long as you have a credit card, you can sign up and take out a bike for free, ride it around as long as you want, and return it to one of several locations before the end of the day. Your card won't be charged a dime.

It's the largest -- and hopefully, most successful -- public bikes program in US history. Similar programs have been attempted in various cities around the world dating back to the White Bicycle of Amsterdam in the 1960s, but most have failed for one reason or another (usually theft).

I took out one of the bikes in Denver, and after a week of chaos and stress, it was just what the doctor ordered. After an hour of biking around an unfamiliar city, feeling truly mobile for the first time in days, I felt like a new man.

And this is precisely what Freewheelin' hopes to accomplish nationwide, and not just at major conventions. The young woman who signed me up explained that the organization is committed to improving both mental and physical well-being through exercise, fighting obesity and diabetes, and making bikes cool again.

Their next step is making helmets cool, too, which aren't required. I asked for one, though, and they were more than happy to provide.