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Trajectories of Vehicle Ownership and Access in American Households

  • Author(s): Brumbaugh, Stephen
  • Advisor(s): Blumenberg, Evelyn
  • et al.

Most American households rely on vehicles for access to employment and other opportunities, but their levels of vehicle ownership may vary over their life course. In this dissertation, I use sequence analysis techniques and longitudinal data from the Panel Study of Income Dynamics to investigate family vehicle ownership trajectories, differences in trajectories across social groups, and changes in vehicles owned by low-income households.

Chapter 1 examines trajectories of family vehicle ownership from 2001 to 2017. Many households have stable levels of vehicle ownership. "Multi-mobility," or owning more than one vehicle per adult, occurs nearly as often as owning no cars. After establishing a typology of trajectories, I construct a model to predict the likelihood that a household takes a certain trajectory type. In the model, a family's starting vehicle ratio has the most explanatory power.

Chapter 2 examines trajectories of vehicle ownership by income, race, ethnicity, and family structure from 2001 to 2017, and by birth cohort from ages 22 to 30. Most groups show stability in vehicle ownership. Vehicle ownership levels are only slightly less stable in low-income households than in other households, in part because other households sometimes experience multi-mobility.

Chapter 3 investigates changes in vehicle holdings among low-income households from 2001 to 2017. Sport utility vehicles (SUVs) account for an ever-increasing share of personal vehicles, despite policies intended to facilitate purchases of more fuel-efficient vehicles. The average fuel economy for owned vehicles increased for all families, but at a slower rate for low-income families.

Transportation planners and policymakers may consider three types of policies to influence trajectories of vehicle ownership. The first involves policies to reduce vehicle ownership, which may have less effect on travel and pollution than expected. The second involves policies to increase ownership among low-income households, which may face political challenges. The third involves policies to maintain ownership, which may be more politically feasible if framed as efforts to help people stay employed.

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