Commodity interaction in freight movement models for New South Wales

The continuous growth in urban population has led to intense competition for space among the various actors in the urban system. Planning and managing this competition requires a better understanding of both personal travel and goods movements. Urban planning in the past has however, focused on providing a sustainable and efficient transport system to solve personal mobility challenges with almost total neglect of the goods movement sector. However, with the growing importance of freight to both local and national economies, and also the disproportionate impacts of freight related activities on congestion, pollution, accidents and other road hazards, there is a stronger call for a better understanding of the freight system. Central to freight movement models is an understanding of where the freight commodities are produced and consumed. An important driver in the production and/or consumption of each commodity is the production and consumption of other commodities. In this paper, these important interactions between commodities are captured in a path analysis freight model which incorporates models of commodity production and consumption. We identify the key factors driving the consumption and production of each commodity. To be suitable for forecasting and policy testing, the estimated models are transformed into linked logit models to also allow for important policy measures such as accessibility and commodity generation influences such as population and employment to be estimated. The proposed model has been implemented to generate the amount of commodity of each type produced and consumed in each state of Australia with illustrations of how the production and/or consumption of one commodity triggers the production and/or consumption of other commodities. The study also demonstrates the differential impacts of changes in demographics or employment growth on the consumption and/production of different commodities. When built into an integrated transport and land use model system that accommodates both passenger and freight activity, and includes models that account for spatial dependency (which is not a requirement of the macro level commodity generation stage), this freight generation capability contribute to the way in which freight movements influence and hence impact on the performance of the entire transport network, for both passenger and freight.