Vegetation is known for enhancing air quality. However, vegetation on urban roads can either increase or decrease exposure to pollutants. The health of pedestrians and cyclists is particularly of great concern since they are directly exposed, unlike drivers. Dispersion of air pollutants is necessary to reduce roadside exposure to air pollutants on urban roads. The local meteorological conditions, street geometric characteristics, and vegetation characteristics influence the dispersion of pollutants on roads. There is a lack of framework for planning urban road vegetation to disperse air pollutants. This study summarized the interrelationship between the local factors on the effect of street vegetation on the dispersion of air pollutants. A conceptual framework was given for planning urban roadside vegetation to reduce roadside users' exposure to air pollutants. Findings from this study clarify the task of planning urban road vegetation to disperse air pollutants.