The progressive tightening of European CO2 emission regulations for light-duty vehicles is driving the automotive industry towards the electrification of conventional powertrains. In this context, mild hybrid systems represent a cost-effective and technically viable solution to improve vehicle efficiency without requiring major changes in overall architecture or the use of large and expensive battery packs. Among the available layouts, the P1 configuration, where the electric machine is mechanically coupled to the internal combustion engine through a clutch or directly to the crankshaft, offers a good balance between complexity, performance, and potential fuel savings, especially for light commercial vehicles (LCVs). This thesis presents the development of a P1 mild hybrid system model, along with its implementation into an existing Simulink model of a light diesel commercial vehicle.