Patricia Mokhtarian– Professor, Civil and Environmental Engineering, Georgia Institute of Technology
Giovanni Circella– Senior Research Engineer, Civil and Environmental Engineering, Georgia Institute of Technology and Researcher, Institute of Transportation Studies, University of California, Davis
California has adopted regional plans to reduce greenhouse gas (GHG) emissions through coordinated transportation and land use planning as required by Senate Bill 375 (SB 375, the Sustainable Communities and Climate Protection Act of 2008) and has committed to reducing overall statewide GHG emissions by 40% below the 1990 levels by 2030 through Senate Bill 32 (SB 32, the California Global Warming Solutions Act of 2006). In order to meet both of these goals, significant changes in household transportation choices must be made.
This study analyzed travel survey and attitudinal data to investigate the impact of household demographics, individual attitudes, and residential location on vehicle ownership and usage decisions in California. The researchers identified characteristics of households that voluntarily choose to own fewer than expected vehicles and travel less by vehicle: they tend to be more diverse, have fewer children, and live in rental units in very high density neighborhoods. Individuals with more pro-environmental attitudes and who like transit, biking and walking are more likely to live in zero-vehicle-owning households, while those who like driving and living in spacious homes with large yards are more likely to be in higher-than-expected vehicle-owning households. The research found that local density has non-linear effects on travel behavior: a given increase in density is associated with larger reductions in households’ vehicle miles traveled (VMT) in lower-density neighborhoods than in higher-density ones, and this difference is larger in smaller regions. Among higher-density neighborhoods, however, density increase is associated with larger reductions in VMT for households living in rail-served regions. These results provide useful insights for promoting the adoption of more sustainable travel behavior, and support the State’s efforts to promote infill development and reduce dependence on personal vehicles, including implementation of SB 375.
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