Aggregate Freight Generation Modeling: Assessing the Temporal 1 oral Effect of Economic Activity on Freight Volumes using a Two-Period Cross-Sectiona

摘要

The most comprehensive publicly available freight databases are the Commodity Flow Survey (CFS)and the FHWA’s Freight Analysis Framework (FAF). These two data sources contain the volume andmovements of freight at high geographic levels, such as state or metropolitan areas. Due to thedifficulty in obtaining freight data at lower geographies various practitioners and researchers havebeen suggesting to estimate freight models based on aggregate data.Following these recent practices, a methodology to estimate a nationwide production and attractionmodels for U. S. domestic trade of goods is presented. To this end, a CFS’s data set provided by U. S.Census Bureau and composed of two-nonconsecutive year period (2002 and 2007) of movement ofgoods between states by 27 industry sectors was used. The state payroll by industry sector, obtainedfrom the County Business Patterns of the U. S. Census, was the variable used to estimate freightgeneration models. The main objective of this paper is to analyze the temporal stability andpredictability of the proposed aggregate models.The results indicate that the payroll alone explains a significant portion of the freight production andattraction at the state level. However, such simplification in the model process did not result inreasonable predictions of freight for a future year horizon. It is recommended that additionally time19dependent factors (e.g. productivity) affecting freight demand should be considered in the modelingprocess.