This is used to influence requirements to drive control strategies and safety attributes in the form of safety design features or safety devices to prevent, eliminate and control (mitigation) safety risk. In the distant past hazards were the focus for very simple systems, but as technology and complexity advanced in the 1970s and 1980s more modern and effective methods and techniques were invented using holistic approaches. Modern system safety is comprehensive and is risk based, requirements based, functional based and criteria based with goal structured objectives to yield engineering evidence to verify safety functionality is deterministic and acceptable risk in the intended operating environment.