Dispersion modeling of traffic emissions in cities

Traffic emissions have a strong impact on air quality in cities. Modeling of dispersion of traffic emissions requires information about the road network, the diurnal and weekly cycle of traffic density, vehicle speed and category, as well as emission factors for the different vehicle categories and typical driving patterns. Furthermore, urban morphology data are important input information for dispersion modeling of traffic pollutants. The release of traffic pollutants takes place within the urban canopy, and their transport and mixing are thus strongly affected by the complex flow patterns in the vicinity of buildings. The paper presents an overview of different modeling studies dealing with the impact of traffic pollution on urban air quality and discusses the type of input data required depending on the resolution of the simulations. The availability of these data and the need for improving databanks providing such information will also be addressed.