Supply and use table based economic indicators in freight generation modelling

Abstract

Freight generation is the corner stone of freight transportation demand models because it is the basis for subsequent steps and of major importance for the quality of demand models. Supply and demand of the economy are the drivers for transportation demand, thus it is state of the art to use economic indicators for freight forecasting. However, the proper transformation of economic activities into freight transportation is still a challenge in freight modelling. In this paper we elaborate the topic of the transformation of economic activity into freight transportation by an approach based on supply and use tables from national accounts. Firstly, the suitability of supply and use tables for the determination of relevant economic activities for the transportation of specific commodities is analyzed. We then scrutinize underlying dynamics of the relationship between the gross value added by economic activities and freight transportation. Lastly, the approach is turned into a freight generation forecasting approach. This approach is based on publicly available statistics (national accounts and transportation statistics) and, thus, does not require expensive or scarce data sources. This approach is particularly useful where neither detailed regional input-output tables nor commodity flow surveys are available. The described approach provides additional insight into the connection between economic activities and transportation, but also provides a reasonably well working approach to demand forecasting for the majority of transported goods and is sensible to changes in economic interaction and outputs. It is useful for aggregated demand models, for instance those scaling existing OD-matrices to achieve the generation step, but also useful for providing marginal totals for more sophisticated models.