01127397

Component

Global climate change is an issue that has received much attention in the past few years. Human travel demand, which results in the burning of fossil fuels and emission of greenhouse gases, is identified as one of the major drivers of global climate change. Fuel consumption and vehicular emissions are both highly dependent on the types of vehicles owned or acquired by households and the miles that are accumulated on the vehicles of various types. It is therefore of importance to understand and model the joint choices of vehicle body type and vehicle usage (measured by miles of travel). In this paper, a joint model of vehicle type choice and utilization is formulated and estimated on a data set of vehicles drawn from the 2000 San Francisco Bay Area Travel Survey. The joint discrete-continuous model system formulated in this study explicitly accounts for common unobserved factors that may affect the choice and utilization of a certain vehicle type (i.e., self-selection effects). A new copula-based methodology is adopted to facilitate model estimation without imposing restrictive distribution assumptions on the dependency structures between the errors in the discrete and continuous choice components. The copula-based methodology is found to provide statistically superior goodness-of-fit when compared with previous estimation approaches for joint discrete-continuous model systems. The model system, when applied to simulate the impacts of a doubling in fuel price, shows that individuals are more prone to shift vehicle type choices than vehicle usage patterns. These findings suggest the need to incorporate joint models of vehicle type and usage in travel demand forecasting model systems so that emissions forecasts can accurately reflect changes in vehicle fleet compositions that may result from changes in system conditions. Moreover, the findings suggest that reductions in emissions (and therefore, global warming) and energy consumption are more likely to accrue from shifts in vehicle type choice (towards more fuel efficient vehicles) than from shifts (reductions) in vehicle miles of travel. This finding has important implications for public policy.

01120148

09-2720

English

0000-0002-0715-8121

29p

2009

Transportation Research Board 88th Annual Meeting

DVD

References; Tables (4)

Climate change; Discrete systems; Exhaust gases; Fuel consumption; Global warming; Greenhouse gases; Pollutants; Public policy; Travel by vehicle type; Travel demand; Travel surveys; Vehicle miles of travel

Copulas; Discrete choice models

Environment; Highways; Planning and Forecasting; I72: Traffic and Transport Planning

Transportation Research Board Annual Meeting 2009 Paper #09-2720

TRIS, TRB

Jan 30 2009 7:05PM