Comparison between measured and calculated concentrations of nitrogen oxides and ozone in the vicinity of a motorway

Exhaust emissions from a motorway have been monitored for a year in a joint project by the State of Lower Saxony and Volkswagen. Measurements were performed by the Fraunhofer Institut für Toxikologie und Aerosolforschung in Hannover. As dispersion models alone are unable to reproduce the behaviour of nitrogen oxides and ozone, a simplified air parcel model has been developed. This model includes, in addition to pure dispersion, some basic reactions of nitrogen oxides and ozone, but neglects reactions with hydrocarbons. A comparison with the observed concentrations shows that the model gives acceptable results if some restrictions with respect to meteorological conditions are taken into account.