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 increases in functional safety failure rates.  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 reports on a method to determine the portion of failure rate estimated from field failure data which is attributable to human factors as opposed to inherent to the safety device itself.  The method is explained and examples of the application of the method are provided.