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Urban transportation -- United States, Climatic changes -- California, Climatic changes -- Washington, Climatic changes -- Oregon, Climatic changes -- Maryland, Transportation planning


Climate change is increasingly recognized as a threat to life on earth. “Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. Limiting climate change would require substantial and sustained reductions in greenhouse gas emissions” (International Panel on Climate Change, 2014, 8).

The transportation sector accounts for almost one-third of all greenhouse gas emissions (GHG) in the United States. Reducing GHG from transportation rests on the “three-legged stool” of improving vehicle efficiency, reducing the carbon content of fuels and reducing vehicle miles traveled (VMT). But “technological improvements in vehicles and fuels are likely to be offset by continuing, robust growth in VMT” (Ewing et al., 2007, 2). Thus, a crucial strategy in curbing GHG from transportation relies on reducing total VMT by promoting alternative modes of transportation hand in hand with promoting development patterns that support the use of such modes, in addition to pricing strategies (for GHG, parking, gas taxes, tolls, etc.) and lifestyle changes to shift from driving. In developing climate action plans, states have begun to acknowledge the connection between transportation and development patterns.

This project explores the institutional barriers and opportunities for reducing VMT, hence GHG, through improved transportation options and smarter development patterns in four states: California, Maryland, Oregon and Washington. The research team analyzed existing policy frameworks around transportation, land use and climate change, outlining the statutory context around plans and actions within state agencies and metropolitan planning organizations (MPOs). The research team used content analysis to analyze existing plans under these agencies, and conducted interviews with over 40 stakeholders to evaluate strengths and weaknesses of state approaches. The research team assessed the existing policy framework within the case study states and offers recommendations for improving existing frameworks. Finally, lessons learned from these four states can inform other states attempting to reduce GHG from transportation.


This is a final report, NITC-RR-789, from the NITC program of TREC at Portland State University, and can be found online at:

Four presentations associated with this final report are attached as supplemental files.

The Project Brief associated with this report can be accessed at



Persistent Identifier

ClimateChange_PIELC_presentation_Lewis.pdf (396 kB)
PIELC Presentation

Lewis_NextGenSummit_ClimateTranspLU.pdf (1575 kB)
Next Generation Summit Presentation

15_TRB_Lewis_1.7.pdf (961 kB)
TRB Presentation

Lewis_OAPA_Climate_Slides.pdf (3155 kB)