Optimisation methods and the classification of city structure: theory and empirical testing

City structure is taken to mean the size and shape of the city and the spatial concentration or dispersal of homes and workplaces. To classify differing structures, a land-use and transport interaction method, based on the classical transportation problem of operations research, is used. The theoretical upper and lower bounds to the amount of journey-to-work travel in the optimal solution leads to the calculation of the urban consolidation index. The behaviour of this index is examined for square and rectangular city shapes of differing sizes and distributions of workplaces. The method is then tested empirically with data on the distribution of homes and workplaces collected for fourteen cities in Australia and East and Southeast Asia ranging in size and land-use density. The relationship between optimisation theory and transport policy is discussed. The approach should prove to be a suitable quantitative method to examine the question of the efficiency of travel in cities both with different concentrations of activity and with different travel behaviour.