When hazards are identified it is beneficial that the resultant set of hazards and actions can be prioritised. This enables separation of those issues that need to be dealt with immediately from minor issues that can act as a distraction. To enable the prioritisation, risk ranking is used.
Unfortunately, many practitioners employ flawed ranking schemes, such as the five by five matrix. The problems with this are best illustrated with an example.
The five by five matrix is a system that has two elements; one aspect looks at the frequency of the occurrence of hazards, the other looks at the potential consequences. Each are scored between 1 and 5. For frequency, a 5 would refer to hazards that occur perhaps a hundred times per year. For consequences, a 5 would refer to a hazard that has the potential for multiple fatalities. A hazard that has a rating of 5 for each of the frequency and consequence ratings would be considered as intolerably. If a SPAD were ranked, then it would be rated as having a frequency and consequence rating as 5 - there are hundreds of SPADs per year and they have the potential for multiple fatality accidents. However, the vast majority of SPADs do not result in any accident; therefore the risk rating applied is too high.
Sotera adopts a system that overcomes that issue by having a third component to the rating that investigates the likelihood that the hazard actually results in the stated consequences. This gives consistent and realistic risk ratings.