An urban planning project in its various stages of preparation poses problems of choice: these decisions become all the more difficult as the variables that figure in the project become more numerous, diverse in character, and closely interconnected. A tool is needed to allow for estimation of the whole of the consequences of a decision or set of decisions. In this paper, an economic model is developed for comparing 2 urban plans. This is a global model that takes account of the different facilities and sectors of activity of the urban area. It is based on the very broad criterion of social welfare function, a function comprised of individual satisfactions that characterize the economic value to the community of the urban planning project being considered. The first part of the paper is devoted to describing the theoretical methods used to produce a workable expression of the difference in social welfare which appears as the sum of the variations in the overall cost. The second part describes the application of these methods to the actual case of the urban area of Saint-Etienne, France. After defining the solutions to be compared, the values obtained for the principal terms which make up the variation in social welfare are discussed, and the importance of these terms relative to person transportation is shown. The computation of these terms requires complete traffic studies employing traffic generation and assignment models.
Abstract