VMT mix modeling for mobile source emissions forecasting: Formulation and empirical application

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Bhat, Chandra R.
Nair, Harikesh S.

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Transportation Research Board of the National Academies


This paper proposes and implements a fractional split model that predicts the VMT mix on links as a function of the functional roadway classification of the link, the physical attributes of the link, the operating conditions on the link, and the attributes of the traffic analysis zone in which the link lies. The fractional split model is an useful formulation for VMT mix analysis because it accommodates boundary values of fractional VMT in a vehicle class, is easy to estimate using commonly available econometric software, and is easy to apply in forecasting mode to predict the VMT mix on each link of a network. The empirical analysis in the paper applies the fraction split model structure to estimate a VMT mix model for the Dallas-Fort Worth metropolitan region in Texas. Results of model evaluation are also presented.


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Bhat, C.R., and H. Nair (2000), "VMT Mix Modeling for Mobile Source Emissions Forecasting: Formulation and Empirical Application", Transportation Research Record, Vol. 1738, pp. 39-48.