Impact of viaduct noise barriers on traffic-induced air pollution in a real urban environment: A Hong Kong case study

Source abstract

Roadside noise barriers are typically installed near residential buildings to alleviate traffic noise. However, their influence on traffic-related air pollution dispersion in dense urban environments remains uncertain. This study uses computational fluid dynamics (CFD) simulations combined with local meteorological and traffic data to assess the impact of segmented viaduct noise barriers. Pedestrian-level PM₁₀ (particulate matter with a diameter of 10 micrometers or less) attributable to traffic emissions is estimated in a high-density urban neighborhood in Hong Kong. The results show that while noise barriers can reduce PM₁₀ concentrations in upwind residential areas by up to 28.5%, increases of up to 7.9% may occur in downwind areas under the prevailing wind. The traffic pollutant is generally retained on the viaduct deck and reduced at the pedestrian level. However, barrier-induced flow deflection and localized ventilation changes contribute to pollutant accumulation near adjacent buildings in some regions. The influence range is primarily confined to tens to hundreds of meters around the viaduct, suggesting spatial redistribution of traffic-related exposure rather than uniform air quality improvement. These findings highlight the importance of site-specific airflow analysis when evaluating the environmental performance of noise barriers in high-density urban settings.