Finding easy modes of transportation seems to be a basic human need, but finding easy and clean modes is becoming imperative. Traffic congestion, overconsumption of fossil fuels and air pollution are all direct results of automotive lifestyles around the world. The logical alternative is human-powered vehicles (HPVs), perhaps best exemplified in the bicycle, the most basic HPV. New high-tech developments in HPVs are not yet ready for mass production, nor are they able to compete with cars. Pedal-propelled HPVs in the air, on land, or under the sea are still in the expensive, design-and-race-for-a-prize category. But the challenge of human-powered transport has inspired a lot of inventive thinking, both amateur and professional.

Innovative bicycle designs. (McGraw-Hill Inc. Reproduced by permission.)

Bicycles and rickshaws comprise the most basic HPVs. Of these two vehicles, bicycles are clearly the most popular, and production of these HPVs has surpassed production...