The bowtie method
The bowtie method is a risk evaluation method that can be used to analyse and demonstrate causal relationships in high risk scenarios. The method takes its name from the shape of the diagram that you create, which looks like a men’s bowtie. A bowtie diagram does two things. First of all, a bowtie gives a visual summary of all plausible accident scenarios (called top event) that could exist around a certain hazard. Second, by identifying barriers the bowtie displays what a company does to control those scenarios. However, this is just the beginning. Once the barriers are identified, the bowtie method takes it one step further and identifies the ways in which control measures fail. These factors or conditions are called escalation factors. There are possible barriers for escalation factors as well, which is why there is also a special type of barrier called an escalation factor barrier, which has an indirect but crucial effect on the main hazard. By visualising the interaction between barriers and their escalation factors one can see how the overall system weakens when barriers have escalation factors.