Today’s automotive industry is moving toward electrification to comply with the increasingly stringent emission limitations but also to succeed in a market more fuel saving-oriented, in a scenario like the depicted one, hybrid electric vehicles (HEVs) represent a suitable solution to satisfy all these new needs. HEVs allow to exploit benefits of electric vehicles without losing the advantages of conventional internal combustion engine ones, but electrification introduces a major level of complexity in first step design and calibration of the hybrid systems. Numerical simulation becomes then fundamental for designers to be able to estimate which could be the best solution, avoiding time-demanding and expensive experiments; the aim of this thesis work was the design and analysis of vehicle models for simulation, both backward and forward.