Courtesy of an excellent Nancy Folbre post:
Increased bicycle use is practical and feasible, especially if it can be combined with effective public transportation for long-distance needs. As John Pucher of Rutgers University (dubbed Professor Bicycle by some of his fans) explains, about 40 percent of all automobile trips in metropolitan areas are less than two miles — a distance easily biked.
I will say that I think the current trend in cycling policy in the United States somewhat tends to overemphasize things like bicycle lanes. It seems to me that if cities acting to remove subsidies and mandate for automobile parking, that this would on its own do a huge amount to spur people to rely more on bikes for appropriate trips triggering the all-important safety in numbers phenomenon. Naturally if lots of people are riding bikes around your city, you should make some lanes. But I think that’s a secondary issue.