Mitigating VMT from Highway Expansion Projects: Early Insights from California

The California Environmental Quality Act (CEQA) requires lead agencies to evaluate the environmental impacts of major projects, including highway expansion projects, and to mitigate those impacts to the extent feasible. In 2013, SB 743 (Steinberg) changed how transportation impacts are evaluated by shifting the performance measure from traffic delay to vehicle miles traveled (VMT), a measure of total driving. This change reflected evidence that the metric of VMT captures the influence that transportation projects have on driving behavior and its related environmental and social impacts, such as greenhouse gas emissions, air pollution, safety, and public health. How have lead agencies implemented the requirement to analyze and mitigate VMT induced by highway expansion projects? To better understand how SB 743 has affected highway expansion projects in practice, we reviewed state regulation and guidance and evaluated the Environmental Impact Reports (EIRs) for the six highway expansion projects that have started the environmental review process since the California Department of Transportation (Caltrans) adopted guidance in 2020 to implement SB 743. In this brief, we focus on how lead agencies propose to mitigate any increases in VMT from each of the six highway expansion projects, including the measures proposed, the extent to which mitigation reduces VMT, the cost associated with mitigation, and sources of funding for VMT mitigation.