A study by Georgia State University shows that trees and bushes near highways greatly diminish air pollution from motor vehicles. Air quality measurements at selected sites with vegetation displayed a 37% decrease in soot and a 7% fall in ultrafine particles compared to non-vegetated locations.

The research highlights that while roadside greenery doesn't solve all pollution issues, it mitigates the severity, particularly given the proximity of 45 million Americans to major highways. The plantings act by trapping particulate matter on their surfaces, but they do not combat carbon dioxide or ozone pollution.

The study recommends urban planning improvements such as expanded public transport and better bike/pedestrian infrastructure as complementary measures to tackle motor vehicle pollution.