Some Problems of Calibrating the Lowry Model

Abstract

This paper describes some problems encountered in developing and calibrating a version of the Lowry model in the Central Lancashire and Nottinghamshire-Derbyshire subregions. The formal structure of the model is presented first, and this provides the background to a discussion of the problems involved in estimating the model's parameter values, and in choosing sensitive and meaningful statistics to measure the model's goodness of fit. It is shown that statistics such as R2 measuring the fit of the distributions of population and employment, are extremely insensitive to changes in the parameter values, and that the most sensitive and useful statistic for calibration is the mean trip length. Certain shortcuts in calibrating the model are also suggested by these results and these can be used to get good first approximations of the parameter values.