The influence of road infrastructure and traffic on soil, water, and air quality.

Polluting substances are spread as a consequence of the construction and use of roads. This article provides a summary of the substances with which traffic pollutes the environment on a local, regional and global level. The mechanisms of dispersion of pollutants to soil and groundwater are described. Based on environmental quality requirements established in rules and regulations in the Netherlands, the paper discusses mitigating measures necessary to limit the distribution of pollutants along highways. Most of the data in this article come from original research carried out by or by order of the Road and Hydraulic Institute. For comparison, other data from the Netherlands have been included. It is shown that source-oriented measures (volume and technical) will have more effect on environmental quality than measures with regard to treating runoff. The use of porous asphalt instead of nonporous asphalt on highways in the Netherlands has environmental benefits. The article also pays attention to combined use of the roadside verges for treatment of runoff using ecological engineering techniques in the form of natural processes in helophyte filter systems in combination with enhancement of ecological values along highways.