The principal transportation mode in the developing world, even in large cities, is still walking because of constraints on the resources needed to operate extensive transit systems. People cover long distances on foot every day and expend human energy that they can hardly spare. Walking under those conditions is an unavoidable burden that consumes productive capability. In North America and Western Europe, however, the attitude and policies are just the opposite: walking is efficient, healthful, and natural. We should do more of it ─ almost everybody agrees ─ and some of the current trends should be reversed. Ironically, among the most popular exercise machines in health clubs and in homes are tread-mills that simulate walking, which could be otherwise accomplished with a transport purpose on the street.