Understanding the impacts of traffic on air pollution is essential to improve methodology of assessment of population exposure which is depending on concentrations of pollutants in the atmosphere. However, concentrations are variable in space, and several parameters influence pollutant concentrations: traffic characteristics, meteorological conditions, pollutant characteristics, road structures, topography etc. In order to improve air pollution assessment methodology, we conducted a review that focuses on parameters that affect spatial variations in studying the link between concentrations and distance to the road for traffic pollutants as PM2.5, PM10, NO2 etc. This step enabled the identification of pollutions classification. Then, we identified external factors as meteorology or road structures, barriers etc. that affect concentrations variabilities on the road and on urban area.