Georgia State University recently published a study revealing that planting trees and bushes along highways significantly reduces the exposure of nearby populated areas to traffic-related air pollution (TRAP).

 
Plants and trees create a vegetative barrier whose large surface area acts as a filter for particulate air pollutants. This is especially important for residential areas near highways, as evidence suggests that motor vehicle pollution is linked with chronic and potentially deadly lung conditions. According to the study, the daily activities of 45 million people in the United States are located within 300 feet of a major highway, regularly exposing them to these particles. After analyzing areas with chain-link fences, solid barriers, and vegetative barriers, vegetative barriers had the most positive impact on air pollution, reducing up to 37% of TRAP. Vegetative barriers also proved most effective when planted downwind of the highway.
Though planting trees and bushes can't address all vehicle pollution factors, lead researcher Roby Greenwald from the GSU School of Public Health said that it can greatly reduce health hazards from particulate air pollution. According to Greenwald, measures to reduce other pollution factors include making more safe and convenient pedestrian infrastructure and public transportation to reduce the need for motor vehicles.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0296885
https://news.gsu.edu/2024/03/18/gsu-study-finds-that-trees-bushes-near-highways-can-significantly-reduce-air-pollution/
https://www.earth.com/news/trees-and-bushes-near-highways-improve-air-quality/#google_vignette