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simulating the influence of depressed roadways.
Figure 1
compares the modeled
concentration gradient with newly-collected independent wind tunnel data.
Fig. 1.
Comparison of normalized ground-level concentrations downwind of a depressed
roadway from wind tunnel observations and algorithm predictions
3. Conclusions and Future Directions
As this work continues to build on our understanding of the relationships between
mobile emissions and adverse health effects and begins to yield tools to assess
roadway impacts and mitigation strategies, it should inform decision making
within EPA and Federal Highway regulatory programs such as the National
Environmental Policy Act, the Conformity rule, and enforcement of the NAAQS.
Additionally, programs within the Departments of Health and Human Services,
Education, and Housing and Urban Development and the Centers for Disease
Control and Prevention will benefit from this research in developing guidelines for
the location of schools, hospitals, and residential housing.
Future plans related to research on dispersion near roadways include the
following: (1) continued improvement of line-source type algorithms for the
AERMOD and hybrid modeling for regulatory applications; (2) further wind
tunnel studies and possible tracer studies to examine boundary layer characteristics,
wind direction and atmospheric stability influences; (3) collaboration with other
EPA laboratories and the FHWA on field campaigns in Las Vegas, Detroit, and
Raleigh to better understand the relationship between traffic emissions and roadway-
related air pollution concentration gradients; (4) computational fluid dynamics
modeling of near-road dispersion to complement wind tunnel and tracer studies;
and (5) use of the improved near-road dispersion models to support planned
environmental health studies in Atlanta as part of an air pollution exposure and
health study with Emory University.
Acknowledgments and Disclaimer
We greatly appreciate collaborations with A. Vette
(EPA/NERL), R. Baldauf (EPA/NRMRL), C. Bailey and R. Cook (EPA/OTAG), and A.
Venkatram (U. Calfornia-Riverside). Although this paper has been reviewed and accepted for
publication by the U.S. Environmental Protection Agency, it does not necessarily reflect its
views or policies.
