Protection of pedestrian zones and residential areas from vehicle emissions by trees and shrubbery planting technique

The article describes the results of in-situ observations and physical model experiments for dispersion of automobile exhaust pollutants by planted areas in urban streets and roads. Structure and composition of protective planting is defined for better dispersion of car emissions. In the "road-shelterbelt-building" system, if the belt height is about half the height of the building, the most effective dilution of pollutants along the building facades and at the pedestrian ways is observed. As the belt height approaches the height of the buildings, the air in yards of the buildings is still cleaner because of the longer way the pollutants have to travel, but then they accumulate within the street space. The shelterbelts for the densely built-up stretches of heavy-traffic streets should be of permeable structure to prevent pockets of stationary air; this ensures the necessary air interchange at the pedestrian ways and also more even pollutant dispersion at the building facades. Guidelines are provided for linear and strip protective/decorative plantation structuring for bringing the environmental discomfort factors in residential areas down to the environmental standards.