California Air Resources Board

CARB’s policy briefs summarize the best available peer-reviewed research on transportation- and land-use-related strategies that reduce vehicle miles traveled (VMT) and related greenhouse gas emissions (GHG). Each brief applies a social equity and justice lens, recognizing that climate strategies must also support fairness and opportunity in communities.

Page contents

• Overview
  • What you’ll find
  • Using the Policy Briefs
• Transportation-related briefs
• Land Use-related briefs
• Research seminar

Overview

The goals of these briefs are to:

• Strengthen the technical foundation of regional planning
• Identify research gaps and data needs to support SB 375
• Inform improvements to the analytical models and tools used by metropolitan planning organizations (MPOs) and other public agencies

CARB first released 23 policy briefs ending in 2014. A 2025 update built on that foundation with new and revised briefs.

What you’ll find

• Evidence-based insights on how specific policies (e.g., increased land use mix) affect travel behavior
• Equity and justice discussions that highlight potential benefits and risks for low-income communities and communities of color
• Information for planners and policymakers on applying strategies in the context of SB 375 implementation

Using the Policy Briefs

Each brief reports the effect size of the policy – how much it changes VMT or other measures of travel behavior per unit of policy change (e.g., a unit increase in density). Effect sizes can be used to predict the outcome of a proposed policy or strategy and are reported most commonly in relative terms (elasticities) which show a percent change in travel behavior relative to the percent change in the strategy. Strategies with large effect sizes and broader possible reach are the most promising for reducing GHG emissions.

Because the accuracy and precision of the estimated effect sizes vary across studies, each brief discusses the quality of the evidence and methodological issues. It is also important to consider that context matters. For example, micromobility services in dense, mixed-use areas may not yield the same results as those in suburban settings. Each brief also includes more detailed discussions about the applicability of study effects.

Each brief also includes a discussion of each policy’s implications for social equity (fairness that accounts for differences in opportunity) and justice (equity of social systems). Achieving both GHG reduction and social justice is a priority for California’s sustainable transportation future. Transportation and land use policies have the potential to repair past injustices, such as redlining and exclusionary zoning, or may reinforce and exacerbate injustices. While most of the reviewed research studies ignore equity, discussions in each brief serve as a starting point for designing fair, community-centered policies by including available research on the strategy’s implications for social equity, health disparities, and justice and, where available, information on how policies can reduce emissions and advance equity when designed with protections, such as creating transit-oriented development with affordable housing for low income residents. The evidence presented in these briefs does not remove the need for authentic community engagement. The authors of these briefs acknowledge that deeper and broader social injustices that were beyond this project’s scope interlock with the specific concerns and opportunities reported and that these briefs serve as a call for future research to consider those broader injustices and center the perspectives of people most affected by these strategies to fully illuminate their implications for social equity, health disparities, and justice.

Transportation-related briefs

Land Use-related briefs

Research seminar

CARB held a 2025 policy brief update seminar with the research team on May 1, 2025. The seminar discussed the outcomes of the strategies, ease of implementation, how quickly they can be expected to take effect, and equity considerations.

Materials from the seminar are available here:

• Seminar recording
• Seminar presentation
• Seminar written Q&A