(63a) Improve the Risk Ranking Process by Categorizing and Detailing Consequence and Probability Categories

The Risk Matrix has long been accepted as a valid methodology for converting hazards to risks and then comparing those risks to each other as a relative risk ranking process. Unfortunately, this is usually a very subjective process relying upon the personal expertise and experience of those performing the review to estimate both probability and consequence of each hazard manifesting itself as an unwanted event. In the end, it is not consistently ?repeatable? and/or ?defendable.? That is, it does not ensure that another group of people with essentially the same information would reach substantially the same conclusion?i.e. ?repeatable.? And because it is so subjective, it does not have sufficient technological grounding to allow it to be defended on its technical merits?i.e. ?defendable.?

This paper proposes ways to enhance ?repeatability? and ?defendability? by providing categories for each level of the probability and consequence axes. This takes advantage of the fact that some information is known and other information is not known. Making several smaller estimates (some with known information) allows a better total estimate to be made. To demonstrate the concept, a 5 X 5 matrix example is used that categorizes each consequence level into four distinct types of consequences and provides three potential approaches for estimating probability, depending on the information available. Criteria for each category are also shown, for illustrative purposes only.

As a look toward future developments, the potential advantages of a three dimensional risk ranking tool are also discussed, with potential axes suggested.