Overview
California’s climate and sustainability policies rely heavily on accurately measuring and reducing vehicle miles traveled (VMT). Under state law, many development and transportation projects cannot be approved without first estimating and mitigating their VMT impacts. Yet the methods currently used to produce these estimates are often imprecise, inconsistent across agencies, and insufficiently grounded in the latest data and research. Such inaccurate VMT accounting means the state may be failing to reduce driving as much as its policies intend, and potentially spending resources inefficiently in the policy implementation process.
UC ITS aims to improve the credibility and accuracy of VMT forecasts used in project-level environmental review across California. The research focuses on both land development projects and transportation infrastructure projects, using emerging data sources — particularly mobile phone location data — alongside traditional methods to produce more rigorous, transparent, and policy-ready VMT estimates.
- Create an improved VMT measurement framework. Develop and validate a VMT measurement framework that integrates mobile phone location data, administrative odometer records (to the extent they are available), and infrastructure sensors. The framework will produce high-resolution, auditable VMT estimates with explicit uncertainty bounds, thereby addressing limitations of current sketch-level tools, travel demand models, and proprietary commercial data products.
- Evaluate current VMT estimation practices by state, regional and local agencies under CEQA for transportation and land development projects. This includes reviewing case studies, interviewing practitioners in California, and examining VMT reduction policies and methods in other states. The goal is to identify strengths, weaknesses, and gaps in current practice.
- Develop improved VMT forecasts for land development and transportation projects. Estimate causal relationships between land development and transportation projects and VMT levels using multiple methods and data sources, including phone-based, survey-based, and sensor-based measures.
- Design “no-build” counterfactual scenarios for forecasting project-level VMT impacts. Examine how to define the appropriate “no-build” counterfactual scenario — a critical and often underspecified element of current VMT mitigation analysis — for housing and nonresidential development projects.
- Develop new empirical estimates of the VMT effects of non-highway transportation projects commonly treated as VMT mitigation measures. This includes transit investments, active travel infrastructure, or streetscape improvements.
Marta Gonzalez
Associate Professor, UC Berkeley
Susan Handy
Distinguished Professor, UC Davis
Elisa Barbour
Assistant Professional Researcher, UC Davis
Jamey Volker
Professional Researcher, UC Davis
