From time to time, I feel obligated to return to my central theme - that bicycling is the most efficient form of human transportation ever devised. (I issue an open challenge - if anybody can refute that assertion, please make your information known!)
Here's some scientific geek-talk found in the Bike Cult book:
When one compares the energy consumed in moving a certain distance as a function of body weight for a variety of animals and machines, one finds that an unaided walking man does fairly well (consuming about .75 calorie per gram per kilometer), but he is not as efficient as a horse, a salmon, or a jet transport. With the aid of a bicycle, however, the man's energy consumption for a given distance is reduced to about a fifth (roughly .15 calorie per gram per kilometer). Therefore, apart from increasing his unaided speed by a factor of three or four, the cyclist improves his efficiency rating to No. 1 among moving creatures and machines.
- Stuart S. Wilson, Scientific American (1973)