8. Frequently asked questions

What are the origins of the bow-tie method?

The method in its current form was developed by Shell following the accident on the Piper Alpha oil rig in 1988. The method was subsequently democratized and promoted through its "large-scale" application in the context of the quantified risk analyses (QRA) initiated in the Netherlands and English-speaking countries.

What's the difference between probability of occurrence and frequency of occurrence?

The concepts of probability and frequency are often confused in hazard studies. Thus, the annual probability of occurrence of a hazardous phenomenon or initiating event is often confused with the annual frequency of these same events. Given the low frequency of such events, this approximation may be considered inconsequential.

What's the difference...