Advanced Safety Management, 3rd Edition

CHAPTER 10THREE- AND FOUR-DIMENSIONAL RISK SCORING SYSTEMS

In all the risk assessment matrices discussed in Chapter 9, “On Hazards Analyses and Risk Assessments,” risk levels are based on the probability of an event or exposure occurring and the severity of harm or damage that could result. Therefore, they are two-dimensional risk scoring systems. For the hazards and risks that most safety professionals encounter, two-dimensional systems will be sufficient. Some risk scoring systems now in use are three or four dimensional.

Safety professionals can expect that variations of numerical risk scoring systems will proliferate. For the knowledge that safety professionals should have, this chapter informs on

• Transitions in numerical risk assessment methods
• Cautions to be considered in using three- and four-dimensional systems, particularly those that diminish the significance of severity potential
• Three- and four-dimensional numerical risk scorings systems
• An extended three-dimensional numerical risk scoring system that includes a method to justify the risk amelioration costs in relation to the amount of risk reduction to be attained
• A numerical risk scoring system developed by this author

TRANSITIONS IN RISK ASSESSMENT

It is typical for engineers to have a passion for quantification and the application of numbers. They become comfortable with statistical measurements. Quantification is stressed in their education. Engineering texts still quote Lord Kelvin who wrote the following ...