An existing full car dynamic model (HVOSM.VD2) was expanded previously to enable simulation of electric, hybrid electric, and fuel cell vehicles with integrated vehicle stability systems. A prototype range extending series hybrid electric vehicle was constructed with independent front wheel drives. A hybrid vehicle stability assist (VSA) algorithm was developed to perform proportional control of yaw rate through left/right distribution of front motor torques while simultaneously blending anti-lock braking and traction control with electric drive within hybrid system power limits. The new model, Hybrid Electric Vehicle Dynamic Environment, Virtual (HEVDEV), was validated and used to simulate the Hybrid VSA safety system in the prototype. Skid pad testing was performed to validate HEVDEV simulations of steady state turning behavior. Further simulations using proportional control of differential front wheel torque predicted stable Hybrid VSA performance during step-steer and braking-in-a-turn dynamic maneuvers within hybrid drive-train power limitations. This study focuses on system transient behavior during step steer inputs using more power intensive PID control algorithms, several front to rear weight distributions, and recent trends in HEV and Fuel Cell component specifications. Conclusions are made about component specifications for successful Hybrid VSA systems in future Plug-In hybrid electric (PHEV) and Fuel Cell (FCV) Vehicles.