A system, method, and safety unit provide safety assurance for a multiple redundant system controlling a plant or complex. A unit active line (UAL) status indicates the presence of at least one redundant active unit within the system. A safety verification line (SVL) status verifies the powered down status of all redundant units not active within the system. A safety unit is associated with a vital supervision card (VSC) and vital power bus and the safety unit controls switchable connections from the vital power bus to the UAL and the SVL. Based on verification of UAL and SVL status, system control includes energizing the UAL.