Instructions on how to use the bowtie models
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 controls can be populated on either side of the model showing:
|Left hand side of the model shows||Right hand side of the model shows|
|Preventative measures which eliminate the threat entirely or prevent the threat from causing the top event recovery||Measures which reduce the likelihood of the consequence owing to the top event being "live" or mitigate the severity of the consequence|
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 as part of an effective SMS.
An everyday example bowtie is available to navigate to demonstrate this explanation. Further guidance is provided on “the bowtie elements”.
Webviewer requires Microsoft Silverlight to operate. This is a free add-on which is available online. If this is unavailable to you, please contact your own IT department for assistance.
Webviewer allows you to navigate around the bowtie in an interactive way. On the left hand side of Webviewer click on the bowtie file.By clicking on the model this bowtie will appear in the Webviewer window allowing you to navigate. Bowtie navigation can be enhanced by using the toolbar. You are able to zoom in and out of the bowtie, make the bowtie full screen, expand levels to easily view the content of the model, chose the display profile (to see the “additional information” on the threats and controls (e.g. effectiveness etc)) and save the bowtie models to your personal computer
Click the button on the toolbar that has four arrows to display a full screen view of the webviewer.