A Hardware in the Loop (HiL) system was developed to investigate heavy truck instability due to loss of control and rollover situations with and without ESC/RSC systems for a wide range of maneuvers and speeds. The purpose of this HiL model is to examine the safety benefits of the emerging electronic stability systems (ESC/RSC) in heavy trucks that are designed to prevent yaw instabilities (e.g., jackknife) and rollovers. This paper outlines the process for validating the HiL model so that the simulation closely represents the expected outcome for a similar maneuver conducted on a test track. The HiL system was built in a laboratory using the brake system of a truck and the actual stability control system control units supplied from a manufacturer. The dynamics software uses TruckSim, and the simulation results were validated using NHTSA collected field data. The HiL model is being used to examine yaw instability and rollover scenarios that would not be possible to conduct in actual track testing. Driving scenarios were developed through an examination of Large Truck Crash Causation Study (LTCCS) cases. These scenarios were based on realistic events and were developed to replicate typical crash situations. The scenarios use a pathfollowing driver model to drive through curves of various radii, a curve with a reduced radius, and variations of lane change maneuvers that are representative of obstacle avoidance. An overview of the scenario development, HiL system design, and the results of the validation of the HiL model are presented. The results of the validation show that the vehicle dynamics and hardware responses of the HiL are comparable to actual heavy truck test track results and can be helpful in determining the benefits of stability control technologies in varied driving situations