Semi-quantitative risk analysis techniques

One of the major benefits of a semi-quantitative risk analysis is that the technique can be applied and results understood by a wide range of stakeholders in the transportation field. Unlike full quantitative approaches, these types of risk analyses do not require specialized risk management experts. Even with the ease of application, however, personnel involved in these activities need to be knowledgeable in the operations under evaluation and the use of semi-quantitative... 

While qualitative techniques represent a very basic analysis, with little modification, they can be expanded and evaluated in a semi-quantitative risk analysis. Additionally, events and scenarios elevated for further analysis can be further evolved by considering the range of potential consequences (small to large) and/or likelihood (low to high probability of occurrence). 

Similar to the process defined for semi-quantitative risk analysis in Chapter 4, quantitative risk is a function of consequence and likelihood. Decisions are made regarding the resnlting risk level and the need for additional risk mitigation based on a comparison of the resnlts to a set of criteria. The QRA process is illustrated in Figure 5.1. The differences between a QRA and the other simpler techniques are ... 

What is LOPA. LOPA is a simplified semi-quantitative risk assessment technique and a hazard analysis tool, mainly deployed to assess the adequacy of IPLs (a requirement set forth in CCPS document). As LOPA is a semi-quantitative method, it uses numerical quantities to estimate the parameters needed to... 

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. 

Figure 4.1 illustrates the risk assessment process for qualitative and semi-quantitative techniques that can be apphed to transportation safety scenarios. Typically, these will be a scenario and issues developed and escalated for more detailed analysis during the identification and prioritization process described in Chapter 3. 

Any of the qualitative analysis techniques can be applied with the selection based on the change being considered. Again, following the risk analysis protocol, issues that cannot be resolved using qualitative techniques should be escalated for a more detailed risk analysis starting with the semi-quantitative analysis technique described in Section 4.3. 

Once a set of recommendations has been developed, the options must be analyzed to determine the benefits, or essentially the level of risk reduction. The risk analysis method utilized to assess the baseline operational risks should be the same method used to analyze each of the potential risk mitigation options. Therefore, if a semi-quantitative technique was used to assess the baseline risk, then the same assumptions, techniques, and risk evaluation criteria (risk matrix, risk index, etc.) should be used to evaluate the effectiveness of the risk reduction options. 

Based on any unacceptable and unmitigated risk identified during hazard analysis, further risk assessment and risk mitigation techniques need to be applied. LORA and conceptual SIS designs based on Risk Matrix can be employed if a qualitative to semi-quantitative method is preferred. Fault tree and event tree analyses with a robust LOPA can be applied if a quantitative method is essential... 

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