Numerous studies have shown
that air pollution increases the risk of different diseases. Moreover, effects
of long-term exposure to air pollution have been proven to cause different
health issues (1, 2). Vehicles
account for a large share of pollutant emissions in urban areas. Vehicles
account for a large share of pollutant emissions in urban areas. Studies have
shown that people living in near-roadway communities (within 100m of the road)
are exposed to the noise and high concentrations, which may be associated with
adverse health effects.
Many studies have been conducted to investigate the
effects of sound wall barriers and vegetation near the roadways on vehicular
pollutant dispersion via experimental or numerical approaches. According to
these studies, sound wall barriers are capable of reducing downwind pollutant
concentrations between 15 and 50%; however, in some specific wind directions,
concentration of pollutants were found to increase compared to cases without
the wall (3, 4, 5).
While studies exhibit
promising benefits from installing near-road barriers, the effects are still
uncertain (6). The effectiveness of sound
walls at mitigating near-road pollution exposure depends on roadway
configuration, local meteorology, and barrier height, design, and endpoint
location. Similar to sound walls, concentrations may be higher behind a
vegetative barrier that is located downwind of the roadway if there are gaps in
the vegetation such as missing or dead trees, or lack of cover from the ground
to the top of the vegetation Models
for quantifying impacts are still under development
EPA and FHWA approved models for air quality
modeling purposes (AERMOD and CAL3QHC/R) currently lack the ability to model
the effects of near-road barriers. This ;
results in reducing the capability of the model in developing feasible solutions to mitigate air pollutant
concentrations in near-roadways areas. Adding a feature to the AERMOD to
consider near-roadway barriers , like what R-Line currently has, enhances the
accuracy of model and will aid in decision making process for EPA, FHWA, and
state DOTs. According to FHWA inventory of noise barrier walls, constructed
noise barrier walls nationwide exceeded 2700 linear miles at a cost of over
$5.4 billion through the end of 2010 (FHWA-HEP-12-044). State
DOT’s will continue to use near-road barriers as an important tool to reduce
the impacts of traffic noise that result from the ongoing improvement of
highways. So it is important to identify the effects on noise barrier on
near-roadway pollutant concentration.
Perry, S. G., Cimorelli, A. J., Paine, R. J., Brode, R. W., Weil, J. C.,
Venkatram, A., … Peters, W. D. (2005). AERMOD: A Dispersion Model for
Industrial Source Applications. Part II: Model Performance against 17 Field
Study Databases. Journal of Applied Meteorology, 44(5), 694–708. http://doi.org/10.1175/JAM2228.1
Wilhelm, M., & Ritz, B. (2003). Residential proximity to traffic and
adverse birth outcomes in Los Angeles county, California, 1994-1996.
Environmental Health Perspectives, 111(2), 207–16.
Baldauf, R., Thoma, E., Khlystov, a.,
Isakov, V., Bowker, G., Long, T., & Snow, R. (2008). Impacts of noise
barriers on near-road air quality. Atmospheric Environment, 42(32), 7502–7507.
Speckart, S. O., & Pardyjak, E. R. (2014). A method for rapidly computing
windbreak flow field variables. Journal of Wind Engineering and Industrial
Aerodynamics, 132, 101–108. http://doi.org/10.1016/j.jweia.2014.07.001
Heist, D. K., Perry, S. G., & Brixey, L. a. (2009). A wind tunnel study of
the effect of roadway configurations on the dispersion of traffic-related
pollution. Atmospheric Environment, 43(32), 5101–5111.