Ultra-safe safety model

The properties of three models of safety the resilience model, the HRO model and the ultra-safe system model. 

The fourth step concerns the ultimate resilience of the resulting model. Safety is often a problem that is even more difficult to control once all the preceding steps have been taken, once the system has become safe or ultra-safe, once the procedures, safety instructions and protective measures have reasonably been followed and adopted by front-line operators, once the management is personally involved in the decisions and fiade-offs in favour of safety, sometimes accepting sacrifices in terms of profitability and once a culture of total reporting is established. In fact no safe system can be completely protected from disasters, and although these are... 

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