A VEHICLE USAGE FORECASTING MODEL BASED ON REVEALED AND STATED VEHICLE TYPE CHOICE AND UTILIZATION DATA. REVISED VERSION

Household vehicle usage behavior by type of vehicle is modeled in the research reported here. Forecasts of future vehicle emissions, including potential gains that might be attributed to introduction of alternative-fuel (clean-fuel) vehicles, critically depend upon the ability to forecast vehicle miles of travel (VMT) by the fuel type, body style and size and vintage of the vehicle. Households acquire different vehicles to satisfy both the transportation needs and the preferences of the household members. Consequently, vehicle usage by type of vehicle can be considered to be a function of three categories of variables: (1) household characteristics, (2) principal driver characteristics, and (3) characteristics of the vehicle itself. The current model is similar to previous models of vehicle allocation and use in multi-vehicle households in that separate equations with correlated error terms are developed for each vehicle in the household. However, this research differs from previous efforts because there are additional equations for principal-driver characteristics that cannot be readily forecast and need to be solved out of the problem; reduced-form equations needed for forecasting purposes are developed through a structural specification of vehicle allocation to drivers. This research is also unique in that the models use both revealed preference (RP) and stated preference (SP) data simultaneously; the models are estimated with a mix of RP and SP observations.