Right-sizing Transportation Infrastructure to Reduce Vehicle Miles Traveled

Research Team: Adam Millard-Ball (lead) and Susan Handy

UC Campus(es): UC Davis, UCLA

Problem Statement: Most of California’s success in reducing transportation emissions over the last 20 years can be attributed to improvements in vehicle efficiency and the adoption of lower-carbon fuels, particularly electricity. California must also reduce vehicle miles traveled (VMT) in order to meet critical climate goals and to enjoy the many co-benefits of reduced driving, such as improved air quality, safety, and public health. Increasing active transportation and transit options are two key strategies that California regions are using to try to reduce VMT, but to date, these projects have not been able to significantly cut VMT. One potential explanation is induced travel demand. Just as adding a highway lane reduces congestion and travel times and thereby induces more people to drive, the same outcome may occur when rapid transit and bike facilities are constructed. As these facilities attract former drivers, congestion is reduced, and more or new drivers backfill the roadway capacity that was freed up.

Project Description: This project investigates two questions. First, to what extent are VMT reductions from transit and active transportation backfilled by induced traffic? Second, is roadway and parking infrastructure the primary, long-run determinant of VMT in congested urban areas? The second question will explore the extent to which infrastructure needs to be sized proportionately to nearby highway capacity if regional and statewide VMT and greenhouse gas reduction goals are to be realized.

Status: In Progress

Budget: $45,000