A threshold model of discretionary travel behavior

Abstract

These remarks are addressed to certain problems raised by Horowitz in his review paper on travel demand theory. The objective of these remarks is to sketch an alternative modeling approach. In particular, a model of discretionary travel behavior is proposed in which trip decisions for individuals are modeled by a simple type of satisficing utility model. The statistical population of such trip decisions is then assumed to satisfy certain independence conditions over space. In the presence of these conditions, the main result of this modeling approach is to show that an exact distribution theory for observable trip frequencies can be obtained. In particular, observable frequency levels are always poisson-distributed, with mean frequencies representable by a classical gravity model. Thus, these models not only provide a simple linkage between micro-and macro-behavior, but also permit the analysis of total frequency distributions (i.e., total travel demand) as well as relative frequency distributions of discretionary travel behavior. These results are developed in section 2, and discussed briefly in section 3. For paper by Horowitz see IRRD 287445.