The bowtie method: A review

The bowtie method is becoming more popular, but it lacks a consistent approach. This article reviews the available literature and identifies the different approaches that are taken. There are two main types of bowties. Quantitative bowties and Qualitative bowties. Most Quantitative bowties use a fault tree together with an event tree and barriers to calculate risk. The ORM bowtie can also be considered a Quantitative bowtie, although its structure is different from a fault and event tree. Qualitative bowties use simpler cause-effect scenarios with barriers to communicate the risk to an audience. It is proposed to allow these variations of the method to exist and be used when applicable. It is also proposed that people using the bowtie method give an additional qualification as to whether they're using a qualitative or quantitative variant.