Road Capacity as a Fundamental Determinant of Vehicle Travel

Abstract

Reducing vehicle miles traveled (VMT) is a central plank of climate policy in California. VMT, however, has proved stubbornly resistant to policies to reduce it. While urban growth has become more compact and public transit service levels have been maintained or increased, these positive trends have not translated into less driving. This report argues that substantial reductions in vehicle travel in congested urban regions can only be achieved through reducing road capacity. It may be difficult to achieve substantial reductions in vehicle travel by relying solely on public transit, walking and cycling, and land use planning for compact, mixed-use development without an equal emphasis on limiting road capacity expansions, and even reducing current capacity.

About the Project

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.