The EUTRM is a demand driven model that can compute GHG emissions in five-year intervals, except for 2015-2030 where every year is modelled. Transport and freight demand are based on purchasing power parity (PPP) adjusted GDP, which is determined by historical and projected gross domestic product (GDP), population, and fuel price for each country. All transport demand is then met with the required transport capacity, whether it be through the sales of passenger cars, buses, and motor bikes for passenger transport activity, or the sale of trucks for freight or additional trains. The relationship between freight transport and GDP has been observed historically, and this assumption is carried forward in time (passenger transport demand shows a slight decoupling with GDP). Thus, an increase of per capita GDP over time will result in an increase of demand for transport and freight. In lieu of policy decisions, this new demand is only met by increasing the fleet size with new vehicle sales. The EUTRM is initialised and calibrated with historical data, whereby for the example of trucks, the vehicle stock and number of new vehicles (both in number and in category), mileage, fuel consumption, and load factor are considered. Vehicle renewal/purchasing is based on retirement curves and freight demand. Exogenous inputs in the model are GDP, population, and fuel price, from which future transport demand can be projected. Only policy decisions will change mode specific parameters. Thus, in the case of trucks, these can include policy driven modal shift (moving freight from road to rail), engine technology uptake (hybrid, electric, hydrogen), and fuel efficiency (efficiency standards). Similarly for cars, passenger activity can be shifted to buses and to walking and cycling, and demand can be reduced through fuel or congestion taxes. Therefore, the strength of the EUTRM is in its ability to combine multiple policy decisions and show their effect on the business-as-usual (BAU) case, and to quantify the relative importance of policies on GHGs. To get more details in the model, the user guide produced by Cambridge Econometrics can be found here. However, over time T&E regularly improves the model in-house.