Publication Detail

NCST White Paper: Cutting Greenhouse Gas Emissions Is Only the Beginning: A Literature Review of the Co-Benefits of Reducing Vehicle Miles Traveled

UCD-ITS-RR-17-38

Research Report

National Center for Sustainable Transportation

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Suggested Citation:
Fang, Kevin and Jamey Volker (2017) NCST White Paper: Cutting Greenhouse Gas Emissions Is Only the Beginning: A Literature Review of the Co-Benefits of Reducing Vehicle Miles Traveled. Institute of Transportation Studies, University of California, Davis, Research Report UCD-ITS-RR-17-38

Traditional evaluation of the transportation system focuses on automobile traffic flow and congestion reduction. However, this paradigm is shifting. In an effort to combat global warming and reduce greenhouse gas (GHG) emissions, a number of cities, regions, and states across the United States have begun to deemphasize vehicle delay metrics such as automobile Level of Service (LOS). In their place, policymakers are considering alternative transportation impact metrics that more closely approximate the true environmental impacts of driving. One metric increasingly coming into use is the total amount of driving or Vehicle Miles Traveled (VMT).

Since passing the seminal Global Warming Solutions Act (AB 32) in 2006, California has enacted two major laws over the past decade that are spurring efforts to reduce VMT: Senate Bill 375 (2008) and SB 743 (2013). SB 375 addresses regional GHG emissions reductions from passenger travel. For each region in the State with a metropolitan planning organization (MPO), the law requires the California Air Resources Board (ARB) to set and regularly update per capita GHG emissions reduction targets for 2020 and 2035. To achieve those targets, SB 375 requires each MPO to adopt a “sustainable communities strategy” (SCS) as part of its regional transportation plan. VMT reductions are a key strategy in SCSs.

Senate Bill 743 (2013) directs the Governor’s Office of Planning and Research (OPR) to revise the guidelines for determining the significance of transportation impacts during analyses conducted under the California Environmental Quality Act (CEQA). SB 743 requires a replacement metric that will “promote the reduction of greenhouse gas emissions, the development of multimodal transportation networks, and a diversity of land uses.” It mandates that “automobile delay, as described solely by [LOS] shall not be considered a significant impact on the environment” under CEQA, except in “locations specifically identified in the guidelines, if any.” VMT is OPR’s currently recommended replacement metric (OPR, 2016).

While state goals for reducing GHG emissions have been one motivation for the shift to VMT measures, reductions in VMT produce many other potential benefits, referred to as “co- benefits,” such as reductions in other air pollutant emissions, water pollution, wildlife mortality, and traffic congestion, as well as improvements in safety and health, and savings in public and private costs. Such benefits may provide additional justification for reducing VMT. In this paper, we review the literature to explore the presence and magnitude of potential co-benefits of reducing VMT, providing California-specific examples where available.