Science is made of facts just as a house is made of bricks, but a collection of facts is no more science than a pile of bricks is a house. Henri Poincare Theaimofthedisciplinesofpraxisisnottheoreticalknowledge. . . . Itistochangetheforms ofaction. . . . Aristotle Transportation systems consist not only of the physical and organizational e- ments that interact with each other to produce transportation opportunities, but also of the demand that takes advantage of such opportunities to travel from one place to another. This travel demand, in turn, is the result of interactions among the v- ious...