The road and railway modules consist of 2 main parts; the emission calculation and the propagation calculation. The emission calculation is always performed inside the Geo-Database where the vehicle numbers for various vehicle categories, the speed of the vehicles, and the road/rail surfaces are fed into a calculation that results in the emission level. The emission level can be the sound power or a sound pressure level in a given reference distance from the road/rail. Emissions are calculated for every section of the road/rail. Where conditions change in traffic speed, volume or surface type, a new emission value is computed.