The Development of a New Gravity—Opportunity Model for Trip Distribution

In this paper the development of a new gravity—opportunity model for trip distribution is presented. Wilson's formalism to obtain the gravity model, and Schneider's intervening-opportunities model are used as the basis for deducing the new model. The notational difficulties associated with the amalgamation of the gravity and opportunity models are circunvented via the definition of an intervening-opportunity matrix. The conventional gravity model is shown to be a particular case of the new gravity—opportunity model. The calibration of the new model is reached by using Furness's matrix calibration procedure together with Hooke and Jeeves's nonlinear optimizing method. Finally, a practical application of the model for estimating intermunicipal passenger flows by public transport, in Southern Brazil, is reported.