A NEW PARAMETER ESTIMATION METHOD FOR UNCONSTRAINED GRAVITY MODELS

— Understanding of gravity models with respect to analytical aspects of entropy maximizing formulas —

Abstract

In this paper, unconstrained gravity model for urban trip pattern is formulated according to the entropy maximizing framework. It is reduced by maximizing the occurence probability of trip pattern subject to the total trip cost, which is the mixture of Wilson's and Sasaki's entropy models. Some characteristics useful to understand the structure of the gravity model were found by a precise observation on an analytical aspect of the model. A new method for parameter estimation for the gravity model is also proposed in our study: parameters for the unconstrained gravity model are estimated only by solving a non-linear equation witch is reduced from constraints of the entropy maximizing problem, and the uniqueness of the estimator has been veriaed mathematically.