Even in a perfectly designed situation, operators will still make occasional errors, just as equipment will have failures. Operator errors may be introduced by poor system/equipment design or by the complexity of operations. Human error assessment refers to the determination of human reliability or performance. As such, it can be used in conjunction with other reliability analyses to determine whether administrative controls to enhance operator performance or hardware changes will provide the greatest improvement in overall reliability/safety.
By conducting human error assessments, one can also obtain a better understanding of whether the human element is performing about as optimally as can be expected, or whether specific design or procedural changes would enhance performance. This evaluation will also make it clearer in reviewing incidents as to whether an operator was negligent or conforming to the standards for the job.
Since formal human error assessment is a complex undertaking, it may be useful to have a company guideline indicating hen it is to be performed. The initiation of human error assessment should be the responsibility of operating management. However, the conduct of the assessment will require the involvement of specialized experts, or other appropriately trained staff, to fully understand and address the human factors issues.
Various detailed sources are available on conducting human error assessments, as are more generalized data bases on human error rates. While the generalized sources may be adequate for overall reliability analyses, key operations and operator vs. automation decisions may warrant or necessitate a human error assessment specific to that particular operation.
In conducting a human error assessment, human factors specialists should be heavily involved. Their analyses should be documented and retained after results are shared with appropriate engineering and operations personnel.
Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety