In the Netherlands there are a number of computer models available for assessing ambient air quality and estimating the impact of specific emission abatement measures. As part of preliminary studies for the government’s Air Quality Innovation Programme, the Ministry of Transport, Public Works and Water Management sought an assessment of the reliability and specific features of these models. This, the resultant study, thus reviews and evaluates the similarities and differences and pros and cons of the computer models most frequently used in the Netherlands to determine air quality in the vicinity of major roads and motorways. The following six models were examined: VLW; CAR-II; the TNO traffic model; the TNO Heaven model; the Urbis (atmospheric) model; and NNM+ (KEMA-STACKS). The substance of this report was written by KEMA, with CE acting as an independent observer to assure the resultant synthesis and analytical conclusions were as balanced as possible. In the course of the project comments were also obtained from TNO-MEP, RIVM and ECN, all of which, like KEMA, have plenty of experience with dispersion models and developed one or more models themselves.