Vehicle modelling is a standard procedure employed today by all the major OEMs in order to comply with the market requirements as well as with the several industrial norms, aiming at reducing the number of modifications during the design phase. For these reasons, its implementation on tools such as Simulink® is of fundamental relevance and constitutes the so-called virtual prototyping process. The aim of this thesis is to examine the longitudinal behaviour and optimize the emissions treatment of a vehicle already present on the market, a 2014 remarkable van. In particular, the attention was shifted on the NOx emissions, being the most relevant emission, together with the particulate matter, in Diesel engines such as the one employed on this van.