Analysis of National County-Level Heavy-Duty Freight Truck Emissions

A national level travel demand model for heavy freight trucks was created to determine the effects of these vehicles on national air quality. A commodity-based freight flow model was created from various data sources to estimate national county-level freight flows. The flows were then converted to truck trips through the use of payload factors determined from the VIUS database. Finally, the truck trips were assigned to a national highway network and heavy freight vehicle VMT was determined on the county level. The model performance was evaluated against both the results for another national level model, the Freight Analysis Framework, and against actual vehicle count data. The estimated truck activity characteristics were then input to a freight truck emissions model to evaluate the air quality impacts of freight trucking. The model represents a new method for the development of freight truck travel demand models by using actual truck travel characteristics to fit the results of the gravity model procedure. This represents a useful advance in working around the lack of trip distribution data in the field of freight activity and air quality modeling.