Abstract: A hybrid electric propulsion system for a vehicle. The system includes an internal combustion engine (12); a flywheel (14) operatively connected to the engine (12), the flywheel (14) having a horizontal rotation axis parallel to a rotation axis of the wheels of the vehicle, the flywheel (14) having a main disk being rotatable in an opposite direction (RFES) with respect to a rotation of the wheels (RT) of the vehicle when the vehicle is travelling forward so as to inhibit a rollover effect of the vehicle when the vehicle is turning; an electric generator (18) operatively connected to the flywheel (14); an electric motor (22) operatively connected to the electric generator (18); and a controller for controlling operation of the engine (12), the flywheel (14), the electric generator (18) and the electric motor (22).