Mitigating roadside air pollution: A critical review of strategies and research practices

Abstract

Traffic-related air pollution remains a major public health concern, particularly near highways. While emission reduction at the source is essential, roadside mitigation strategies can help reduce local exposure. This review provides a comprehensive assessment of mitigation strategies for open-road environments, including solid, vegetative, and combination barriers, as well as filtration systems and purifying asphalt. A total of 82 studies (2000-2024) were analysed, focusing on pollutant reduction, underlying mechanisms, influencing factors and research methodologies. Solid barriers generally provide the most consistent reductions, while combination barriers show the greatest long-term potential. Emerging technologies such as filter systems and photocatalytic materials remain promising but require further optimization. This review critically examines the methodologies used across studies and identifies key limitations that hinder comparison and optimization. We outline research priorities among which standardized protocols, long-term monitoring, integrated experimental–modelling approaches, and interdisciplinary exposure-based assessment frameworks.

Keywords: Traffic-Related Air Pollution, roadside mitigation, dispersion, deposition, air quality management, green infrastructure