This paper shows that the gravity model is not a single model but that there is a whole family of spatial interaction models. The properties of this family are outlined in some detail. Basic concepts of such models can be developed in a variety of ways, and these are illustrated. The paper then outlines a number of other theoretical developments, and is particularly concerned with the disaggregation of such models, with the incorporation of time variables, and with the relation of spatial interaction, to more general, models. Uses of spatial interaction models are outlined briefly and the final section of the paper draws a number of conclusions and presents a summary.

A family of spatial interaction models and associated developments

A relationship between the gravity model for trip distribution and the transportation problem in linear programming

This paper explores the relationship between spatial structure and spatial interaction at the intraurban level. To examine this relationship an experimental framework is designed based on the application of a doubly constrained entropy-type gravity model to journey-to-work data for twenty-four Canadian urban areas. The study demonstrates that distance-decay exponents are strongly influenced by geographic structure and the geometry of origins and destinations. As such, both the influence of map pattern and the friction of distance should be explicitly incorporated into spatial interaction models. The paper also explores the impact of city size and the nature of the economic base of the urban area upon distance-decay exponents. (a) (TRRL)

A.W. Evans

Papers

Some properties of trip distribution methods