8.7 Quantification

Most research effort in the human reliability domain has focused on the quantification of error probabilities, and therefore a large number of techniques exist. However, a relatively small number of these techniques have actually been applied in practical risk assessments. For this reason, in this section only four techniques will be described in detail. More extensive reviews are available from other sources, e.g. References 5, 6 and 7. Following a brief description of each technique, a case study will be provided to illustrate the application of the technique in practice. As emphasised earlier, quantification has to be preceded by a rigorous qualitative analysis in order to ensure that all errors with significant consequences are identified. If the qualitative analysis is incomplete, then quantification will be inaccurate. It is also important to be aware of the limitations of the accuracy of the data generally available for human reliability quantification.

The various techniques that are available represent different balances in the extent to which they attempt to model the full richness of the large number of factors that are likely to impact on human performance in real situations, or adopt a simplified approach that enables them to be used more easily by analysts without a specialised knowledge of human factors principles.