Design of road-side barriers to mitigate air pollution near roads

Abstract

We quantified the effects of the use of solid barriers on the dispersion of air pollutants emitted from the traffic of vehicles on roads located over flat areas, aiming to identify the geometry that maximizes the mitigation effect of air pollution near the road at the lowest barrier cost. Toward that end, we systematically used the near road CFD (NR-CFD) model that simulates the physics occurring in the atmosphere in a small computational domain (<1 km long) by numerically solving, via computational fluid dynamics (CFD), the equations that describe the dynamics of the atmosphere in the near surface layer (ASL) (<250 m high). Results from the NR-CFD model were highly correlated (R2>0.96) with the SF6 concentrations measured by the US-NOAA in 2008 downwind a line source emission, for the case of a 6m near road solid straight barrier and for the case of without any barrier. We considered the effects of different geometries, sizes, and locations. We observed that, under all barrier configurations, the normalized pollutant concentrations downwind the barrier are highly correlated (R2>0.86) to the concentrations observed without barrier. Best cost-effective configuration was observed with a quarter-ellipse barrier geometry with a height equivalent to 15% the road width and located at the road edge, where the pollutant concentrations were 76% lower than the ones observed without any barrier.