The origins of bowtie are to be found in a simplified fusion of fault and event tree
methodologies.
In the 90’s the oil and gas industry founded and developed the practical application of bowtie
as a tool to facilitate a better understanding of how risks were being managed. The benefits of the
methodology have since been recognised in numerous other industries including defence, medical,
financial and the aviation industry.
A barrier-based approach to risk
The aviation community are mostly familiar with Prof James Reason’s model, referred to as ‘Swiss
cheese’ and the bowtie is a barrier-based structure illustrating this approach. This method
is also referred to in ICAO’s Safety Management Manual (SMM) document referencing defensive
barriers in accident causation with ICAO Annex 19 referring to understanding and appreciating
safety risk controls
Bowtie achieves this by not only identifying the controls (or barriers) in place but also
looking at control failure mechanisms (as escalation factors) and in turn how these are managed (as
escalation factor controls). 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 the
aviation industry.
The barrier approach of the bowtie, while most often used as a proactive risk assessment tool,
may also be of benefit for the reactive classification of safety events as evidenced by the
development of the Aviation Risk Management Solutions (ARMS)
Safety Issue Risk Assessment (SIRA) tool.