Bowtie achieves a good understanding and appreciation of safety risk control by not only identifying the controls (or barriers) in place but also looking at control failure mechanisms and in turn how these are managed. Based on these considerations, insights are gained into the organisation’s risk mitigation strategies and therefore into the appropriate management of safety resources.
The main strength of the barrier approach is as a qualitative tool, which is a practical solution for the challenges of risk assessment in the dynamic operating environments of industry.
The Bowtie model consists of different elements that build up the risk picture. The risk picture revolves around the hazard (something in, around or part of an organisation or activity which has the potential to cause damage or harm) and the top event (the release or loss of control over a hazard known as the undesired system state).
Consideration is then turned to the threats (a possible direct cause for the top event), consequences (results of the top event directly ending in loss or damage) and the controls (any measure taken which acts against some undesirable force or intention).
The Bowtie model explores the escalation factors (the reasoning to why a control may not be defeated or less effective) of all controls allowing the allocation of escalation factor controls. These prevent the escalation factors having an impact on the prevention or recovery controls. Further attributes, such as control effectiveness or criticality can be allocated to the Bowtie model to evaluate the risk picture.