Risk ranking matrix

Using a tool such as a qualitative risk ranking matrix can be very useful in identifying low-risk buildings. For those events that have potentially major or catastrophic consequences to buildings and their occupants, however, a qualitative risk matrix may not always be an appropriate final evaluation. For events that are potentially major or catastrophic, regardless... 

Risk indices are single numbers or a tabulation of numbers that are correlated to the magnitude of the risk to people. Some risk indices are relative values with no specific units. The limitations on the use of indices are that they may not be an absolute criteria for accepting or rejecting the risk. Risk indices also do not communicate the same information as individual or societal risk measures. An example of risk indices is a risk ranking matrix. Table 6-4 (modified from CCPS, 1992) shows how severity and likelihood are combined to obtain risk indices. An example risk matrix is shown in Figure 6-3 (RRS, 2002). 

In this particular risk ranking matrix, the risk level is not inversely equal, i.e. C4 PI do not carry the same risk as P4 Cl. Generally it is considered the risk is higher when the consequences are more severe rather than when frequency is greater). 

Once the specific issues and scope of the analysis are defined, a semi-quantitative risk assessment may be conducted using either risk indexing or a risk ranking matrix. The risk indexing and risk matrix techniques should be built on the information from the earlier analyses. Each level of risk analysis should not be considered a separate effoit, but a continued understanding of the transportation issue. Additionally the information gained from these activities can be used to update the qualitative analysis, especially benchmarking comparisons. 

Table 3.3-3 presents the risk ranking matrix used to compare all hazards and accident scenarios identified in the PHA and FMEA. A discussion of each risk measure is also provided. The risk ranking results serve as the basis for determining if a more detailed, quantitative analysis of specified hazards or accident scenarios is required. 

In this particular risk-ranking matrix, the risk level is not inversely equal, i.e.,... 

Prioritize toe significance of toe event using a risk-ranking matrix (see below). 

The following example of a basic priority risk-ranking matrix system is provided to display one tool for determining whether the change or trigger event is simple - and able to use a short form PSSR - or more complex, thus in need of a long form PSSR. 

To comply with item 6, operators have to identify the major hazards they face, estimate the frequency and consequences of each risk, combine the frequency and the consequences in some kind of risk-ranking matrix, and finally set some criteria for determining which are the high-priority risks. Some operators chose to identify the risks by the outcomes, such as a derailment or a collision, while other operators chose to identify the root cause of the risk, such as brake failures, defective vehicles or track-circuit failures. 

Each cell in tlie matrix (Table 18.4.2) is assigned a risk ranking as indicated by the letters. In this approach, an A level risk corresponds to a very severe consequence with a high likelihood of occurrence. Action must be taken, and it must be taken promptly. At tlie other end of the scale, a E level risk is of little or no consequence witli a low likelihood of occurrence, and no action is needed or justified. For example, a level C risk might warrant mitigation witli engineering and/or administrative controls or may represent risks tliat are acceptable with controls and procedures. 

The reason this rather small-scale accident is mentioned next to the two large-scale accidents noted above is that this minor case presents a potential risk. Recalling the risk assessment matrix (Figure 4.2), it is not hard to imagine that such a small-scale accident could have had very serious consequences, ranking it as a potentially extremely hazardous case. In this context, even a small-scale accident could have the potential of an environmental disaster. 

Once the hazards have been identified, and their causes, consequences, and frequencies discussed, the team should risk rank each identified hazard scenario. If a risk matrix is used then the estimated risk values for the two scenarios are B and C, respectively. 

Having an accepted and well-understood risk assessment matrix makes reaching consensus easier to assess the severity of consequences, determine event probability, define the risk, and rank risks in priority order. 

Semi-quantitative techniques, consisting of index and matrix methods. Examples are Dow Fire and Explosion Index, Mond Index, and Pipeline Index for risk ranking of different facilities of the same type, and the matrix method for risk ranking of potential hazardous events that a given facility or organization can face. 

A number of qualitative hazard identification methods are available to the risk analyst. Some of the more popular ones are discussed here. Further detailed information can be found in CCPS (1992). These methods become more powerful tools if they are coupled with the matrix-based risk-ranking scheme previously described. 

The issues raised in a Road Safety Assessment could simply be ranked as low, medium or high risk. A more objective method would be to use a Risk Assessment Matrix such as that shown in Table 9.1. A risk score of 1-3 is low risk, 4—9 is medium risk, and 12—16 is high risk. 

Definition of hazard, risk discussions on likelihood, consequence risk — register, matrix, ranking. Consequence ranking, preliminary hazard analysis tolerance point—ALARP refreshing on mathematics, fault tolerance, plant ageing, and basic functional safety fail safe operations in plants. 

RISK REGISTER, RISK MATRIX AND RISK RANKING... 

Risk Register, Risk Matrix and Risk Ranking... 

From Clause 4-3.3 it is clear that the most common form of qualitative risk analysis is the risk matrix and risk ranking (Chapter I). Generally, preliminary hazard analysis (Clause 4.0 of Chapter I) is done to obtain rough knowledge about the risk profile for... 

From these data a risk matrix as discussed in Chapter I (Table 1/3.3.2-5) is produced. The risks are ranked as detailed as in Chapter I. After risk ranking, safety measures as discussed in Clause 1.7.5 shall be applied. 

---