The impact assessment is based on the national strategic transport models developed in the Finnish Transport Agency’s methods development programme. The analyses of projected impacts are described in more detail in a separate report. 

The impact assessments use computational models to provide broad and diverse
information about the kilometre tax system and its effects on individual passengers and the transport system as a whole. For this purpose two separate, mutually complementary assessment models have been developed: the individual model and the transport forecasting model. The individual model simulates the choices made by individual people in different parts of the country, while the transport forecasting model assesses the national impacts at the transport system level. The forecasting model therefore is effectively a change model that only predicts changes in the relative proportion of different modes of transport as a result of changes in transport supply and costs. This is the primary objective of the forecasting model because it is easy to change and analyse the model’s description of transport system especially in future scenarios. The individual model, then, is based on small grid cells, allowing local demand to be modelled with much greater accuracy. At the same time, however, it is much harder to provide a detailed description of transport systems. The two-model approach therefore effectively combines the strengths of different methods.