Ali Mekky

Abstract

This paper is concerned with the evaluation of the Gravity Model (GM concept), and its applications from both philosophical and operational points of view. The main concern will be the model as a simulator for a trip distribu-tion phase of the transportation planning process, although some of the critic-isms apply to the other applications of the model as well.In section 2 the GM will be presented on the basis of an analogy with New-tonian mechanics, statistical mechanics and information theory. The generalised form of the GM and its modal split implications which have been developed in the frame-work of Entropy Maximising (EM) methodology will be described briefly. In section 3 the GM will be evaluated from the philosophical, perform-ance, and operational points of view. EM approach will be considered through-out the work as a methodology which leads to a special case of GM which we shall call Entropy Maximising Gravity Model (EMGM). A derivation of GM without total cost constraint will be developed. Summary and conclusions will be given in section 4.

Ali Mekky, Department of Traffic Research Alexandria Region General Transport Administration, and Economic Academy, Cracow