bowtieanalyses

BowTie analyses, or Bow-Tie analysis, is a risk assessment method that visualizes how a hazard can lead to adverse consequences and how this risk is controlled by preventive and mitigative barriers. The approach combines concepts from fault tree analysis and event tree analysis into a single diagram, centered on a top event or hazard and flanked by cause pathways on the left and consequence pathways on the right.

The diagram comprises three main elements. On the left, threats or initiating events that could cause the top event are linked to preventive barriers designed to stop the progression toward the top event. In the center is the top event itself, representing the point at which control is lost or a critical incident occurs. On the right are the possible consequences and the mitigative barriers intended to limit severity or prevent escalation. Barriers are typically categorized as preventive or mitigative and are assessed for effectiveness, reliability, and monitoring. Residual risk is considered after barrier performance.

Developing a Bow-Tie analysis involves several steps: defining the hazard and top event, identifying credible threats and potential consequences, listing and evaluating protective barriers, and assessing barrier effectiveness and gaps. The method is often used to support risk communication, barrier management, and governance in high-hazard industries such as oil and gas, chemical processing, aviation, healthcare, and nuclear power.

History and use: Bow-Tie analysis emerged in the risk management community in the late 20th century, with adoption by several industries to provide a clear, visual representation of risk pathways and controls. Its strengths include intuitive visualization, explicit linkage of causes, controls, and consequences, and facilitation of barrier improvements. Limitations include a qualitative emphasis, potential oversimplification of time dynamics, and dependence on the accuracy and completeness of input data.