2006 Outstanding Dissertation – Xinyu Cao

Suburban sprawl has been widely criticized for its contribution to auto dependence. Numerous studies have found that suburban residents drive more and walk less than residents in traditional neighborhoods. Accordingly, smart growth programs have been advocated as a means to reduce auto travel.

However, most studies have established only an association between the built environment and travel behavior, but not a causal relationship. Their connection may be more a matter of residential choice than of travel choice. For example, residents preferring walking may selectively live in walkable neighborhoods and thus walk more. If so, the effects of land use policies may be overstated.

Using data collected from 1682 respondents living in four traditional and four suburban neighborhoods in Northern California in 2003, this dissertation explored this causal link by employing a quasi-longitudinal research design and controlling for residential self-selection (namely, residential preferences and travel attitudes). Specifically, we investigated the influence of the built environment on various measurements of personal travel choices including uses of different modes (driving, transit, walking, and biking), trip frequencies for different purposes (overall travel, nonwork travel, shopping travel, and strolling), auto ownership, and vehicle type choice.

The results showed that residential preferences and travel attitudes have pervasive influences on all measurements of travel choices. The results also provide some encouragement that land-use policies designed to put residents closer to destinations and provide them with alternative transportation options will actually lead to less driving and more walking.

Taking the evidence from all our analyses together, however, neighborhood design appears to have a stronger influence on walking than on driving. In other words, the residential environment promoted by smart growth programs may be an effective strategy to encourage walking but have less effect on driving, especially after attitudinal predispositions are accounted for. Given that walking is an inadequate substitute for driving, the smart growth movement seems to be more of a solution to public health problems than to transportation problems. Even so, it will give residents a choice to drive less and walk more and this choice is highly valued by a large proportion of respondents in our data as well as in other studies.

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