Comparison of Commodity Flow Forecasting Techniques in Montana

Abstract

Two methods for developing commodity flow forecasts at a substate level of geography are described. The first process is a simplified method that relies entirely on the commodity percentage increases provided at the state level in the FHWA freight analysis framework database. The second method uses a combination of substate employment data and input-output analysis to distribute the forecasted growth for each commodity to each zone in the study area. The differences between these two methods are shown geographically and in table form at the county level of detail. Additionally, a chi-squared goodness-of-fit test is used to determine whether the two forecasting methods are statistically different for inbound, outbound, and internal flows. Most of the analysis was taken from the commodity flow freight forecast created for the Montana Department of Transportation highway reconfiguration study. The results of this comparison are discussed in the context of the transportation planning decisions that potentially are improved by using the enhanced rather than the simplified forecasting method.