Human error in bowtie

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How human factors & human error can be taken into account in the bowtie method

Human factors & human error can negatively influence safety in complex industries, activities and processes. This means that human factors & human error need to be considered in bowtie risk assessment; otherwise you are lacking and ignoring crucial information. In this section, a common pitfall with the inclusion of human factors & human error into the bowtie method is discussed and useful guidelines are proposed in how human factors & human error can be effectively included in bowties.

In bowtie risk assessments, human factors & human error can be found in two places:

  1. Threats: human factors or human error appear as a threat in a bowtie when the human act or condition is able to directly cause a top event (see Figure 1).
  2. Escalation factors: human factors or human error can appear as an escalation factor in a bowtie when the human act or condition can defeat or reduce the effectiveness of a barrier (see Figure 2).
Figure 1. Relation of human factors & human error with threats
Figure 2. Relation of human factors & human error with escalation factors

There is a common pitfall for including human factors & human error into bowties for both the threat and escalation factor element. The common pitfall is that human factors or human error is described in generic terms, such as ‘Human factors’, ‘Human error’ or ‘Operator error’. Ultimately they might be true, but it does not add a lot of context or extra information to the bowtie. Moreover, the generic terms for describing human factors & human error often results in the identification of generic barriers and recommendations such as ‘Training’ and ‘Procedures’ (see Figure 5). Therefore it is useful to define which specific human act or condition can impact the bowtie scenario to add value to the bowtie. This pitfall can be circumvented by describing the human act or condition that could cause the top event (for threats, see Figure 3) or by describing the human act or condition that defeats or reduces the effectiveness of the barrier (for escalation factors, see Figure 4).

Including and describing more specific human factors & human error with the guidelines outlined in this section, will help to identify specific barriers and recommendations to improve safety (see Figure 5). Also, this approach facilitates risk communication since the information is more explicit which makes it easier to comprehend (see Figure 5).

Figure 3 – Improving the bowtie risk assessment by describing the human act or condition that could cause the top event instead of a generic term
Figure 4 – Improving the bowtie risk assessment by describing the human act or condition that could defeat or reduce the effectiveness of a barrier instead of a generic term
Figure 5 – The impact of using the guidelines in this section (making it easier to identify specific safety measures & the diagram is easier to understand)

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