Air Quality

Why Air Quality Matters

The quality of the Atlanta region’s air impacts public health and overall quality of life. Because vehicle emissions are a significant contributor to air pollution, air quality is a major consideration in the region’s transportation planning.

The Atlanta region must meet the continuously tightening air quality standards set by the Environmental Protection Agency (EPA). These standards focus on two primary pollutants: ozone, a gas that forms in the atmosphere from tailpipe emissions, smokestacks and other sources; and particulate matter, tiny bits of particles in the air produced by car and truck exhaust, power plants, manufacturing facilities and other sources. ARC uses a variety of tools to understand air quality in the Atlanta region.

Air Quality and Transportation Planning

The Atlanta Regional Commission (ARC), the federally designated Metropolitan Planning Organization (MPO), is responsible for developing a  Regional Transportation Plan (RTP) and Transportation Improvement Program (TIP) to meet state and federal air quality standards.

The RTP, a long-range blueprint that guides future transportation investments, includes transportation projects that mitigate congestion or provide alternative mobility options to achieve these air quality standards.

The TIP, the short-term blueprint that guides current transportation investments, allocates federal funds for use in the construction of the highest-priority projects in the RTP.

The Conformity Determination Report (CDR) is a required document that accompanies the RTP and TIP. The CDR demonstrates that the projects contained in the RTP and TIP conform to air quality standards. Whenever major changes are made to RTP or TIP project lists, a new CDR must be produced.

The U.S. Department of Transportation (USDOT), along with the EPA, reviews the RTP to determine whether it conforms to air quality standards. If it does not, federal transportation funds could be withheld from the region.

Air Quality and Transportation Policy

The Transportation & Air Quality Committee (TAQC) is a 35-member body that serves as the transportation policy committee for the ARC Board and represents a 20-county area. TAQC meets monthly at the Atlanta Regional Commission.

View upcoming Transportation & Air Quality Committee meetings.

What is Ozone?

Unlike other gaseous air pollutants, ground level ozone is not directly emitted by a source. Ozone is formed when volatile organic compounds (VOCs) and nitrogen oxides (NOx) react with extreme sunlight. Sources of VOCs and NOx include coal-fired power plants, gas stations, natural sources and gasoline-powered vehicles.

ozone graphic

In the short term, ozone can impact the respiratory system, causing irritation to the nose, throat and lungs. The long-term effects of ozone can be compared to repeated sunburns and can lead to permanent scarring of lung tissue, loss of lung function, and reduced lung elasticity.

Ozone Monitoring and Standards

In Georgia, the ozone monitoring season runs from March 1 to October 31, when temperatures are highest. However, ozone can be a problem year-round for sensitive populations. The Georgia Environmental Protection Division (EPD) collects ozone monitoring data in Georgia and establishes emissions budgets for the Atlanta region to attain EPA standards.

EPA’s current standard, set in 2015, for 8-hour ozone is 0.070 parts per million (ppm). A 7-county area of the Atlanta region is currently classified as a “marginal nonattainment area” per the 2015 ozone standard. To understand ozone levels in the Atlanta region, see the Environmental Sustainability page on ARC’s DASH.

What is Particulate Matter?

Fine particulate matter (PM) is a term for particles and liquid droplets suspended in the air. PM originates from a variety of sources including diesel trucks, power plants, wood stoves and industrial processes. Health risks range from mild respiratory and cardiovascular issues to premature death from heart and lung disease.

Particulate Matter Monitoring and Standards

In December 2012, EPA set a new annual standard of 12 micrograms per cubic meter, tightening the previous 1997 standards of 15 micrograms per cubic meter. By meeting the 2012 standard, the Atlanta region also satisfies the 1997 standard. To understand how transportation impacts PM levels in the Atlanta region, see the Atlanta Roadside Emissions Exposure Study (AREES) on ARC’s DASH.

Tools for Air Quality

Atlanta Roadside Emissions Exposure Study (AREES)

AREES spatially depicts air quality throughout the 20-county Atlanta region, focusing on particulate matter concentrations resulting from the transportation system.

Congestion Mitigation and Air Quality (CMAQ) Calculator

In an effort to standardize best practices in evaluating CMAQ projects, the ARC developed a modular CMAQ emissions calculator. The tool highlights changes in NOx, VOC, PM2.5, and greenhouse gas emissions and, where applicable, vehicle hours of delay and vehicle miles traveled. It calculates benefits for 14 types of strategies including, but not limited to:

  • Transit enhancements,
  • System operations strategies,
  • Alternative fuels,
  • Demand management strategies, and
  • Bicycle and pedestrian investments.

To learn how the CMAQ Calculator is applied in the TIP Project Evaluation Framework, see the Transportation Improvement Program on ARC’s DASH. The calculator is currently calibrated only for the Atlanta region but can be customized and adopted for other regions throughout the country.

Disclaimer: The calculator was developed by Texas A&M Transportation Institute, using data and input parameters specifically tailored to the Atlanta Region for use by the Atlanta Regional Commission (ARC); any subsequent use of the Calculator by anyone other than ARC shall be at the sole risk of the user.

CMAQ Calculator Download

Motor Vehicle Emissions Simulator (MOVES)

The Motor Vehicle Emissions Simulator (MOVES) is the U.S. Environmental Protection Agency’s (EPA) tool for estimating emissions from highway vehicles. MOVES has been used in Georgia since 2010 and for all Atlanta area conformity determinations since 2013. MOVES2014 was used to support The Atlanta Region’s Plan, which was adopted in February 2016.