Letter from Mayors to U.S. DOT on Carbon Performance Standard


The Honorable Anthony Foxx
U.S. Department of Transportation

Dear Secretary Foxx:

On behalf of the millions of people living in America’s cities and towns, I urge you to include a greenhouse gas (GHG) performance standard in the proposed congestion and air quality rule for surface transportation. 

Cities represent the future of America.  By 2050, nearly 70 percent of the world’s population will live in cities.[1] While strong urban centers provide many important benefits, cities also face unique challenges. Despite accounting for just 2 percent of landmass, cities produce 70 percent of the world’s CO2emissions.[2] This sad reality jeopardizes the health of urban residents. Carbon emissions from vehicles, and other related pollutants released by the combustion of fossil fuels from driving, lead to significant health problems. For instance, smog, which worsens a host of respiratory and cardiovascular illnesses, is formed when pollution from cars and trucks reacts with sunlight. Carbon pollution, in particular, exacerbates this problem by raising global temperatures thus speeding up the requisite chemical reactions, leading to greater smog formation and more illnesses.[3] While harmful for all residents, the effects of carbon driven smog formation disproportionately impact vulnerable populations, especially children and the elderly.

We must act now to safeguard public health and protect our planet, and that starts with reforming our transportation system to better account for the impact our transportation projects have on climate and health. Currently, 26 percent of U.S. greenhouse gas emissions come from the transportation sector, and 84 percent of emissions in the transportation sector come from tailpipes. Including a carbon emission performance standard in the proposed congestion and air quality rule must be part of the solution, and is a key component of President Obama’s plan to tackle climate change. 

Your department has already been a leader in developing regulations and programs to boost the fuel economy of the nation’s vehicle fleet, reducing greenhouse gas pollution that puts our cities, economy, and transportation infrastructure at risk. Now is the time to build on that track record by using your administrative rulemaking authority to include carbon emissions as an air pollutant in the proposed performance-management rule for congestion and air quality developed pursuant to MAP-21. 

Specifically, the proposed rule should require that states and Metropolitan Planning Organizations (MPOs) set targets for reducing carbon emissions and develop implementation strategies to achieve those targets as part of their long-range transportation plans. This rule should require that local transportation agencies report on those strategies in each update of their transportation improvement program. This will help generate smarter transportation policies in and around America’s cities, lowering GHG emissions and making cities cleaner and healthier.

Several MPO and state planning programs assess GHG emissions and include strategies for reducing them, most notably in California. But without a uniform standard, it will be challenging for federal, state, and local agencies faced with limited revenue, increased congestion, and growing demands for transportation to make informed, rigorous, and transparent long-range plans that tackle climate change. 

The inclusion of a standard in the proposed congestion and air quality rule is an essential step for U.S. DOT to fulfill its pledge to “take actions to ensure that Federal transportation investment decisions address potential climate impacts in statewide and metropolitan transportation planning and project development processes as appropriate in order to protect federal investments.”[4]

Relevant federal statutes, SAFETEA-LU and MAP-21, along with applicable legal precedent fully support the inclusion of GHGs as an “air pollutant” in this instance. In 2007, the Supreme Court in Massachusetts v. EPA, found that the Environmental Protection Agency can regulate greenhouse gases, such as CO2, from vehicles as “air pollutants” under the Clean Air Act. U.S. DOT is free to apply the same meaning to the term “air pollution” as used in 23 USC § 134(a).

Therefore, I strongly urge you to support including a carbon performance measure in the new rule. 






[1] World’s Population Increasingly Urban With More than Half Living in Urban Areas, United Nations. Accessed at:


[2] How Cities Can Save Trillions, Curb Climate Change, and Improve Public Health, World Resources Institute. Accessed at: http://www.wri.org/blog/2014/09/how-cities-can-save-trillions-curb-clima….

[3] U.S. Global Change Research Program, Climate and Health Assessments Key Findings. Accessed at: https://health2016.globalchange.gov/air-quality-impacts#box-248

[4] U.S. Department of Transportation Climate Adaptation Plan 2014, U.S. Department of Transportation. Accessed at: http://www.cakex.org/sites/default/files/documents/2014-%20DOT-Climate-Adaptation-Plan.pdf