Data on pollution from traffic can help plan mass transit

Vehicles crowd roadways during the morning rush hour in North Raleigh.
Vehicles crowd roadways during the morning rush hour in North Raleigh. News& Observer file photo

As any motorist who travels through the Triangle as part of the daily commute can attest, the Wake County region continues to grow at a fast pace. With this growth comes increased transportation needs, as evidenced by the complex web of interstates and other major thoroughfares that traffic in the Triangle flows through every day.

The Jan. 5 news article “540 loop extension in southern Wake won’t start construction until 2020” outlined the N.C. Department of Transportation’s plan that will guide road construction in the region for the next 10 years, including several widening projects and redesign of major traffic arteries. The Board of Transportation is expected to finalize the plan this summer.

One aspect that it is often overlooked in the development of new road construction projects is the resulting air emissions from the cars and trucks. Air pollution from traffic-related emissions can affect human health in a variety of ways, including increased asthma, decreased lung function and heart disease. In the United States, 1 in 5 people live near heavily traveled roads, which makes understanding the impact of traffic emissions on public health a critical environmental health and medical issue.

Previous research studies on the topic have concluded that air pollution from traffic in the United States was either the largest or second-largest emission sector to cause premature death. However, these studies were limited in their ability to characterize the concentrations of the emissions and their resulting impacts in the immediate vicinity of the highways.

A recent study by researchers at the UNC Institute for the Environment and the UNC Gillings School of Global Public Health builds on these previous studies by utilizing computational models to more closely refine the public health impacts of air pollution. To test this new methodology, researchers estimated the public health impacts of traffic-related emissions in North Carolina’s Piedmont region, which has a population of over 4 million people.

One innovative component of the new methodology allows for the identification of hot spots – where pollution concentrations are highest – near roadways, especially along interstate highways. Not surprisingly, the results show that the most public health impacts from traffic emissions are found in the population centers of Raleigh, Charlotte and Greensboro – the three largest cities in the state. Furthermore, utilizing the new methodology scientists found that previous estimates of the health impacts of air pollution from traffic sources have been underestimated.

The results of this study provide valuable information for state and local policymakers in regards to addressing mobile-source emissions and providing motivation for exploring options for mass transit. In addition, the results of this study can inform state officials as they decide how to allocate millions of dollars for environmental mitigation projects provided to North Carolina as a part of the recent Volkswagen settlement.

The same approach used in this study also can be scaled up for an analysis to provide insights on the impacts of these emissions on a national level.

Although the findings and conclusions of this study are but a small piece of evaluating the impacts of more road construction and increased traffic on public health, the results pave the way for a more robust analysis and understanding. That understanding will inform future policy decisions that should benefit residents of the Triangle, North Carolina and throughout the country.

Sarav Arunachalam is a research associate professor at the UNC Institute for the Environment.