Heterogeneity in the Relationship Between Vmt and the Built Environment: A Quantile Regression Approach

Vehicle miles traveled (VMT) is a primary policy variable because it is strongly correlated with greenhouse gas emissions and the density and diversity of urban environments. Policies that increase density and diversity of land use are believed to decrease VMT presumably by replacing it with nonmotorized travel. This causal inference has not been conclusive and may create further disparities by gentrification and an increase in long-distance travel for lower-income commuters. In this paper, we explore the heterogeneity in the relationships between personal level VMT and the built environment, accessibility to opportunities and open spaces, and people’s socio-demographic traits across various levels of travel demand. The present research first develops opportunity-based measurement of residential land-use indicators at the US census block level for the whole California. This is followed by a Latent Profile Analysis using the land-use indicators to identify distinct land use patterns for all the census blocks in California delineating residential built environment characteristics. Using the data from the 2012-2013 California Household Travel Survey, we estimate quantile regression models to understand the heterogeneity in the relationships between VMT and residential built environment characteristics and people’s socio-demographic traits. The results indicate different sensitivity to land use at various travel intensities implying different response to land use policies.