Air Quality Planning Program


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SCAG’s Air Quality Planning Program coordinates with various air quality and transportation stakeholders in Southern California to ensure compliance with the federal, state, and regional air quality requirements.  Federal Clean Air Act Section 176© (42 U.S.C. 7506(c)) requires transportation conformity to ensure that federal funding and approval are given to highway and transit projects that are consistent with (“conform to”) the air quality goals established by a state air quality implementation plan (SIP). Conformity, to the purpose of the SIP, means that transportation activities will not cause or contribute to new air quality violations, worsen existing violations, or delay timely attainment of the national ambient air quality standards (NAAQS).​

As the federally-designated Metropolitan Planning Organization (MPO) for the six-county Southern California region, SCAG is required by law to be responsible for the transportation conformity determination on the Regional Transportation Plan/Sustainable Communities Strategy (RTP/SCS) and the Federal Transportation Improvement Program (FTIP).  SCAG is also responsible for preparing the regional transportation strategy and control measures portion of the Air Quality Management Plan (AQMP) for the South Coast Air Basin. In addition, SCAG provides the socio-economic growth forecast and transportation activity projections to all the air districts in the SCAG region. 

Resources & Links

U.S. Environmental Protection Agency

U.S. Department of Transportation

California Air Resources Board

California Department of Transportation

  • Air Quality Analysis and Coordination
    The Caltrans Headquarters Air Quality Branches manage Department air quality analysis and Transportation Conformity policy, assist Caltrans District Office Environmental and Planning staff with regional and project-level air quality issues, consult and coordinate with State, Federal, and regional air and transportation planning agencies, build and maintain air quality analysis tools and guidance, and manage research studies related to transportation air quality issues.

Air Quality Districts

Universities and Research Centers

Non-Governmental Organizations

  • Surface Transportation Policy Partnership
    Surface Transportation Policy Partnership (STPP) is a diverse, nationwide coalition working to ensure safer communities and smarter transportation choices that enhance the economy, improve public health, promote social equity, and protect the environment.
  • Coalition for Clean Air
    Coalition for Clean Air is dedicated to restoring clean, healthy air to California by advocating for effective public policy and practical business solutions.
  • Environmental Defense Fund
    Guided by science and economics, the Environmental Defense Fund aims to find solutions to the most serious environmental problems.
  • American Lung Association, State of the Air
    The American Lung Association aims to protect people from air pollution impacts that lead to lung disease and other related harmful effects.

What’s New

Proposed rules, revisions, approvals and determinations.


Greenhouse Gases

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Greenhouse gases (GHG) are gases that trap heat in the atmosphere including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases.  The effect of each gas on climate change depends on how much of the gas is in the atmosphere, how long the gas stays in the atmosphere, and how strongly the gas impacts global temperature. Read more about Greenhouse Gas Emissions on the EPA website.