COMMODITY FLOW MODELING

The project reported on here was undertaken with the primary objective of creating a database of commodity flows into and out of the counties of Indiana and to allocate this commodity traffic to the transportation network of the state. Such a database was to form the foundation for a general transportation model for Indiana that would assist state decision-makers in evaluating the various alternatives for public investment in the transportation infrastructure of the state. The project had two phases. The first phase was completed in 1993. This paper covers the second phase of the project. The organization of this paper follows a classical transportation planning process. It begins with an identification of the study area and the existing transport network, or networks in the present case. This is followed by a discussion of the commodities examined and the commodity traffic generation for the counties of Indiana. The models developed for estimating the production and attraction of these commodity flows are also presented and discussed. Distribution of the traffic from origins to destinations is accomplished using a gravity-type of distribution model. This is followed by the use of a modal split procedure, which allocates traffic to specific modes of transport on the basis of historical (1993) patterns of mode use. The final component of this process is an assignment of the distributed traffic to links of the appropriate modal network. This process was undertaken here for nineteen groups of commodities that include the entire range of manufactured goods, coal, farm products, non-metallic minerals, and waste products. There is also some analysis of mail flows, although much of this is at a rudimentary level of analysis due to a lack of data on these flows. The end result of the above process is a database that can be used to estimate future flows on Indiana's rail and highway networks. This estimation of future commodity traffic flows was accomplished with traffic projections for 2005 and 2015.