What is bowtie analysis?
The bowtie method comes from the process safety industry and is now used for occupational safety, quality, cyber security and operational risk. Its strength is communication: one diagram shows the whole risk story and the controls that matter, so operators, managers and auditors share the same picture. It complements barrier-focused incident investigation with barrier analysis, and the risk ratings in a risk matrix.
Building a bowtie diagram
- Hazard: something with the potential to cause harm, in normal operation.
- Top event: the release of the hazard, the loss of control.
- Threats: what could cause the top event (equipment, people, environment, materials).
- Consequences: what could result (harm to people, product, environment, business).
- Barriers: the controls on each line, in the order they act.
- Escalation factors: what could defeat each barrier.
Bowtie example
The example analyses a quality risk: the top event "wrong label applied to product" on a packaging line that runs several products. Three threats (leftover labels from the previous batch, a wrong label roll from the warehouse, an artwork error in a new label version) and three consequences (wrong product reaching a patient, a recall, a regulatory observation) are shown with their barriers. Two barriers are weak: the line clearance checklist, which is signed without a physical check, and the first-article check, under time pressure at launch. Those are the controls to strengthen first.
What makes a good barrier?
- Effective: it can stop the sequence on its own when it works.
- Independent: it does not share a failure cause with other barriers on the same line.
- Auditable: its condition can be checked, and someone owns it.
- Specific: "training" or "procedures" alone are usually supporting activities, not barriers.
How to use this Bowtie Analysis tool
- Define the hazard and top event. Click the hazard and the knot to describe the hazard and the moment control is lost.
- Add threats. List the causes that could lead to the top event on the left.
- Add consequences. List what could happen after the top event on the right.
- Add barriers. Use the + buttons to add prevention and mitigation barriers on each line.
- Assess the barriers. Rate each barrier as effective, weak, failed or not assessed, and add owners and escalation factors.
- Export. Export the bowtie diagram and the barrier tables to PDF, PNG or Excel.
Frequently asked questions
What is a bowtie analysis?
A bowtie analysis is a visual risk method that shows, on one diagram, how a hazard can be released (the top event), the threats that can cause it, the consequences that can follow, and the barriers that prevent the top event (left side) or mitigate its consequences (right side). Its shape resembles a bow tie.
What is the top event?
The top event is the moment control over the hazard is lost, before any damage is done: for example "loss of containment", "loss of control of the vehicle" or "wrong label applied". It should be a specific event, not a consequence or a cause.
What is the difference between prevention and mitigation barriers?
Prevention (proactive) barriers sit between a threat and the top event and stop it from happening. Mitigation (reactive) barriers sit between the top event and a consequence and reduce its effect or likelihood. Each barrier should be effective, independent and auditable.
What are escalation factors?
Escalation factors are conditions that can make a barrier fail or degrade, such as time pressure, lack of maintenance or a disabled alarm. They can themselves be controlled by escalation factor barriers. In this tool you can note an escalation factor for each barrier.
How does bowtie relate to fault tree and event tree analysis?
The left side of a bowtie is a simplified fault tree (causes of the top event) and the right side a simplified event tree (outcomes after it). Bowtie trades the calculations of those methods for a clear picture of the controls that everyone can understand.