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Quantifying the Impacts of Human Factors on Functional Safety

It is not difficult to think of numerous ways in which human factors might impact functional safety. For example, imperfect repair, improper calibration, faulty installation, etc. can all contribute to decreases in functional safety performance. However, if actions are to be taken to mitigate these impacts then it is essential to have some quantitative measure of the impacts so that the actions’ effectiveness can be assessed. This paper describes how the Site Safety IndexTM (SSI) is used to adjust safety metrics, computed under the assumptions that human factors play no part in safety system performance, to reflect the effects of human factors on safety system performance on a site by site basis. Examples of the application of the method showing the safety performance changes attributable to human factors are provided. 

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