Influence of Roadway Emissions on Near-Road PM_2.5: Monitoring Data Analysis and Implications

Sonoma Technology scientists examined PM_2.5 concentrations measured at 48 near-road monitoring sites across the U.S. in 2017, identified roadway contributions to PM_2.5, and forecasted how fleet-turnover could affect near-road concentrations over time. Results will help inform agencies as they identify transportation projects of local air quality concern (POAQC). <br>

This work was completed as part of Sonoma Technology's work on the <a href="/projects/4431">Transportation Pooled Fund.</a href><br>

The results of this study were published in <a href="https://www.sciencedirect.com/science/article/pii/S1361920920306295?via%3Dihub" target="_blank">Transportation Research Part D: Transport and Environment.</a href><br>

The abstract of the article is below: <br>

Transportation projects must undergo a transportation conformity hot-spot analysis if they are designated as projects of local air quality concern (POAQC). We examined concentrations of particulate matter 2.5 µm in aerodynamic diameter or smaller (PM_2.5) measured in 2017 from 48 near-road monitoring sites across the U.S. Annual average PM_2.5 increments, the difference between near-road and background PM_2.5, were between 0.1 ± 0.2 µg/m³ and 2.0 ± 0.2 µg/m³ for sites without noted confounding factor(s). The highest PM_2.5 increment from monitors ten or more meters from the roadway was 1.4 ± 0.2 µg/m³. Using modeled national average exhaust emissions, and associated near-road contribution to PM_2.5, the upper bound of 2.0 ± 0.2 µg/m³ is projected to decrease 30% from 2017 to 2040, for the types of highways assessed here, assuming a roadway with 8% heavy-duty diesel vehicles and constant traffic volumes. These results can help inform transportation conformity POAQC designations.