The causality issue has become one of the key questions in the debate over the relationships between the built environment and travel behavior. Although previous studies have tested statistical and/or practical significance of the built environment on travel behavior, few have quantified the relative roles of the built environment and residential self-selection in influencing travel behavior. Using 1,479 residents living in four traditional and four suburban neighborhoods in Northern California, this study explores the causal effect of neighborhood type on driving behavior and its relative contribution to the total influence of neighborhood type. Specifically, this study applied Heckman's sample selection model to separate the effect of the built environment itself and the effect of self-selection. The results showed that, on average, the effect of neighborhood type itself on driving distance was 25.8 miles per week, which accounted for more than three quarters of the total influence of neighborhood type and 16% of individuals' overall vehicle miles driven. These results suggest that the effect of the built environment on driving behavior outweighs that of self-selection. This paper also discussed the advantages and weaknesses of applying the Heckman's model to address the self-selection issue.
Bibliographical noteFunding Information:
Acknowledgements The data collection was funded by the UC Davis-Caltrans Air Quality Project, the Robert Wood Johnson Foundation, and the University of California Transportation Center. The survey was designed by Susan Handy and Patricia Mokhtarian. Thank Ed Vytlacil for his help on technical issues of sample selection models. Comments from two anonymous referees have greatly improved this paper.
Copyright 2009 Elsevier B.V., All rights reserved.
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