sonROAD18 is a road traffic noise emission model developed on behalf of the Federal Office for the Environment (FOEN). It is based on the formalism of the European model CNOSSOS, but uses the SWISS10 vehicle categories and thus represents the current vehicle fleet in Switzerland. In addition, emission values for buses and trams as well as agricultural vehicles are available. The emissions of an individual vehicle are characterised by means of the radiated sound power in one-third octave band resolution and as an A-weighted sum level. In addition, a directivity term accounts for the decrease in emission strength towards high elevation angles. In contrast to the previously used model StL-86+, sonROAD18 also covers the low speed range and allows predictions down to 20 km/h. The figure shows as an example the speed dependency of the sound power level for four vehicle categories. Besides total noise, the two components propulsion and rolling noise are shown.