Abstract: The training aid described herein is used to train operators of equipment, generally heavy mobile equipment, and comprises a briefcase-sized unit having a connector cable within releasably connects to the control systems and indicators on the vehicle, which have been modified in several ways. The control unit in the briefcase is capable of either simulating one or more abnormal conditions in the equipment by overriding normal readings such as on indicators, meters or alarms, or additionally actual abnormal conditions can be created in the equipment by degrading brakes, the retarder system, hydraulic steering mechanism, or actually killing the engine or the propulsive power of the unit.