What if cities trying to reduce air pollution and traffic made bicycles available for free on their streets? Some European communities have been trying this out for years. There's even one car-dependent suburban Atlanta community that's had a program like this. The typical setup is simple: The bikes, which are usually painted bright yellow to deter people from stealing them, can be picked up and dropped off at various locations around town on the honor system. Now The San Francisco Chronicle reports that that city is in the process of setting up a free bike-sharing program. Other cities that have expressed interest in doing the same include Washington D.C., Portland, Ore., Chicago and New York. Clark thinks this is a really great trend that could help increase the life expectancy of our population. Our average lifespan is about 79 years, a figure that's lower than in other nations around the world because of our sedentary lifestyle. Bike-sharing programs are one way to encourage people to get moving.