Computable spatial economic equilibria and freight network modelling

This paper investigates, both from a theoretical and an empirical perspective, the issue of integration between economic models of spatial competition and freight networks’ models. An abstract integrated model should combine assumptions and characteristics of models belonging to different classes: multiregional input-output and spatial computable general equilibrium models, spatial price equilibrium and network equilibrium models. The formulation of an integrated framework is made easier by mathematical similarities in the structure of equilibrium problems, that allows the paper to define a single fixed-point problem which, in turn, can be expressed either as a model of constrained maximization or as variational inequalities or non-linear complementarity problem. The Walrasian and Wardropian theoretical paradigms could then be combined and used as working assumptions in applied models of freight traffic forecast, improving the poor predictive performance observed in currently available models. Actual implementation of an integrated model, however, requires the solution of a number of statistical and computational problems that are not immediately evident from the theoretical formulation. In this paper some of these problems, including scale differences, parameters estimation and solution algorithms, are described and briefly discussed, and some solutions are suggested. The conclusion is that a reconciliation between available data and theory seems possible, although at the price of some unavoidable approximations.