Risk Assessment, 2nd Edition

9 Bow‐Tie Analysis Methodology

Georgi Popov¹ and Bruce Lyon²

¹ University of Central Missouri

² Brown & Brown

OBJECTIVES

• Introduction, History, and Overview
• Review Fault Tree Analysis, Event Tree Analysis, and Bow-Tie Analysis Methodologies
• Provide Guidance on the Use of Bow-Tie Methodologies
• Examine the Use of Bow-Tie Methodologies, their Strengthens, and Limitations

9.1 Introduction

Bow‐Tie Analysis is a relatively new and simple tool that is used to analyze and communicate risk pathways and controls in selected hazard scenarios. It is one of many “barrier‐type” risk models available to assist in the identification and management of risk. The “Bow‐Tie” name is derived from the shape of the diagram created in the analysis.

One of the benefits of a Bow‐Tie diagram is that it gives an overview of multiple plausible scenarios and associated controls and consequences, in a single picture that would be difficult to explain otherwise. It helps stakeholders to identify, evaluate, and communicate existing controls for selected hazards in a given scenario. The International Organization of Standards (ISO) 31010 nationally adopted by American National Standard Institute ANSI/ASSP/ISO 31010‐2019 Risk Management – Risk Assessment Techniques standard describes Bow‐Tie Analysis as “a graphical depiction of pathways from the causes of an event to its consequences.”

This chapter will demonstrate the use of the Bow‐Tie method and its applications in OSH risk assessment and risk reduction ...