Commodity interaction in Freight movement models for Greater Sydney

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 based freight model which incorporates models of commodity production and consumption. We identify the key factors driving the consumption and production of each commodity together with their elasticities. To be suitable for forecasting and policy testing, the estimated models are transformed into linked logit models that allow for important policy measures such as accessibility and commodity generation powers 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 others commodities. When built into an integrated transport and land use model system, this capability adds a richness to the way in which freight movements influence and hence impact on the performance of the entire transport network, for both passenger and freight