The methodology is used to identify and assess critical tasks. Its implementation involves five (5) phases.
- Identify Critical Tasks Performed
- Analyze each Critical Task to the Appropriate Level of Detail
- Qualitatively Assess Risks Associated with Critical Tasks
- Identify Risk Control Strategies
- Incorporate the Results of Applying the Methodology into the Safety Case
1) Identify Critical Tasks Performed on an Installation
The result of performing this stage is a list of critical tasks requiring further analysis.
The activities required to develop this list are as follows:
- Review the generic critical-task inventories to identify which tasks are performed on the installation.
- Review the non-critical tasks in the generic task inventories to identify where tasks are performed on the installation which, for whatever reason, have a higher
criticality than that considered at the generic level. - Identify tasks perform<id on the installation that are not covered by the generic task inventories. Apply the criticality diagnostics questions to these tasks to identify those that should be included in the list of critical tasks requiring analysis.
2) Analyze each Critical Task to the Appropriate Level of Detail
Each task identified as critical in stage 1 will be analyzed using HTA. However, the level of detail of this analysis will be kept to a reasonable minimum based on the
depth of analysis tool developed for this methodology. For the generic critical-tasks the level of analysis required will have already been determined. Other tasks
performed on an installation and identified as critical will be analysed using the tool.
The Depth of Analysis tool gives three options:
- Low criticality level analysis means that only the top level of the HTA is performed. This identifies what subtasks are performed but does not go on to describe how they are performed. This is the default level of analysis for all critical tasks.
- Medium criticality level analysis means that the first level of the HTA is re-examined to determine which of the sub-tasks are most critical. Only the most critical subtasks are analyzed further.
- High criticality level analysis means that the whole task is analyzed in detail.
The output from this stage of the methodology is set of analyzes of all the tasks identified as critical in the first stage.
3) Qualitatively Assess Risks Associated with Critical Tasks
At this stage, each of the critical tasks is examined to determine what types of errors may occur, their likely consequences, and possible opportunities for recovery. This is based on the task analyses developed in stage two hence the detail at this stage depends on the results of the depth of analysis .assessment for each task.
The output from this methodology stage is a qualitative assessment of risk associated with each of the tasks identified as critical. This provides useful input to stage 4 of the methodology. It also provides information about human errors that act as accident initiators and the actions performed that allow recovery and mitigation. The results of this stage should be used during other risk analyses performed for safety cases.
Finally, it will also provide insight into activities performed on an installation that may have been overlooked during the first two stages of the methodology. This may prompt a reassessment of some tasks.
4) Identify Risk Control Strategies
Having identified the risks associated with tasks, it is necessary to identify appropriate methods of preventing human errors and supporting recovery so that those risks are minimised. The main options available include hardware modification, the provision of written instructions, the design of information systems interfaces, task-specific training, and competency assessment.
5) Incorporate the Results of Applying the Methodology into the Safety Case
The overall aim of the methodology is to ensure that human factors are adequately covered in safety cases. The methodology thus guides the review team in the
identification of information to be included in the safety case.
Source: https://www.hse.gov.uk/research/otopdf/1999/oto99092.pdf