Land Use and Vehicle Miles of Travel in the Climate Change Debate
In this paper, Marlon G. Boarnet, Douglas Houston, Gavin Ferguson, and Steven Spears analyze the nonlinear relationship between land use and VMT and related thresholds. Based on a travel diary survey in the greater Los Angeles area, the authors estimated the effects of regional employment accessibility on VMT in different locales. They divided their sample into quintiles. For households in the third and fourth quintiles of employment accessibility, they estimated that the elasticity of VMT with respect to employment accessibility is -0.83 (based on a spline regression) and -1.16 (based on a stratified sample). These results are as much as three to four times larger than those predicted in other studies. This suggests that policy makers should focus on employment accessibility at the metropolitan level, instead of neighborhood population density, when designing their public transportation and CO2 emissions policies.
Although the authors found that easy access to rail does not have a significant impact on VMT, living near a bus station does reduce automobile use. Locating near a freeway also reduces VMT, but this effect is confined to households that are within 10 miles of a freeway. Based on these results, the authors argue for a transport–land use policy that focuses on employment subcenters. It should link residences to job centers through a combination of various transportation infrastructures. They caution, however, that such a policy in some places will yield a stronger reduction in VMT than in others, because the relationship between transport–land use planning and VMT is nonlinear.
This paper was presented at the Lincoln Institute’s Land Policy Conference of 2010 and is Chapter 7 of the book Climate Change and Land Policies.