Risk relative quantification

Because most research effort in the human reliability domain has focused on the quantification of error probabilities, a large number of techniques exist. However, a relatively small number of these techniques have actually been applied in practical risk assessments, and even fewer have been used in the CPI. For this reason, in this section only three techniques will be described in detail. More extensive reviews are available from other sources (e.g., Kirwan et al., 1988 Kirwan, 1990 Meister, 1984). Following a brief description of each technique, a case study will be provided to illustrate the application of the technique in practice. As emphasized in the early part of this chapter, quantification has to be preceded by a rigorous qualitative analysis in order to ensure that all errors with significant consequences are identified. If the qualitative analysis is incomplete, then quanhfication will be inaccurate. It is also important to be aware of the limitations of the accuracy of the data generally available... 

Of course, quantitative risk assessment is still necessary, even when ecological models are used, but in addition to specific, absolute quantifications, a main area of ecological models could be relative risk assessments Which application scheme is more efficient in terms of interest, for example, control efficiency, effects on nontarget organisms, and costs ... 

E. Quantification of Relative Risks from Toxic Chemicals. 394... 

The first step in designing a road safety development index (RSDI) is to come up with a comprehensive set of indicators, which includes as far as possible aU the main parameters in road safely of human-vehicle-road-enviromnent-regulation, instead of considering a few factors such as accident rates per population or per kilometoe driven. In addition, this index should be as relevant as possible for different countries, especially in developing countries. The choice of accident risk and exposure variables is necessary to what is available in international data and what is considered necessary for meaningfiil comparisons. Commonly, frequencies of aimual numbers of vehicles, accidents, injured and killed people are some kind quantification and relatively easy to define and to measure in different countries. But differences in definitions, noncollection of data, non-rehabUity of data and under-reporting are problems for effective measurements of road safety. 

A simplified fire safety evaluation of a building (see Table F.2). It consists of analyzing and scoring hazard and other related risk parameters to produce a rapid and simple estimate of relative fire risk. A detailed fire risk evaluation may not include attributes such as human behavior and attitudes. The structure of a risk index system facilitates quantification and inclusion of such factors. Where a quantitative fire safety evaluation is desirable, detailed fire risk assessment may not be cost-effective or appropriate. Fire risk indexing may provide a cost-effective means of fire safety... 

Semiquantitative methods are used to describe the relative risk scale. For example, risk can be classified into categories such as low, medium, high, or very high. The number of levels of risk can vary from (say) a to b. In a semiquantitative approach, different scales are used to characterize the likelihood of adverse events and their consequences. Analyzed probabilities and their consequences do not require accurate mathematical data. Semiquantitative assessment is useful especially if quantification of risk is difficult. At the same time, qualitative interpretation is too subjective. As already discussed, the risk graph (highly project dependent) discussed in Chapter 1 in conjunction with available guided risk nomogram or LOPA approach, is commonly used for this purpose. Here discussions wiU be mainly on the LOPA approach (LOPA wiU be dealt with separately later). 

Since catastrophe events are, however, relatively rare, there is a pervasive lack of reliable experience data on their likelihood and consequences. Therefore, assessing and pricing catastrophe risk constitute challenges that would persist until the appearance of numerical simulation models during the second half of the twentieth century. Thanks to this innovation, the quantification of probabilities and effects of physically complex catastrophes slowly starts becoming a standard practice. 

An example of seismic risk assessment and prioritization for restoration of damages is presented for the port of Thessaloniki in Greece. In this application, the port facilities are classified into main, important, and secondary through appropriate ranking of the value of the exposed elements, based on various factors that describe the role of each element in the system. In that way, the global value of each element at risk depends not only on its direct specific value or content (physical and human) but also upon its indirect/immaterial value that is represented by the usefulness and relative role in the whole urban system, at a specific time. Three periods are identified in respect to the occurrence of an earthquake event normal, crisis, and recovery. Global value evaluation in different periods could be a powerful tool for the prioritization of pre-earthquake actions and quantification of the... 

The benefits to be gained from risk assessment are not, in any way, dependent on quantification. All the benefits to be derived can be derived by systematic qualitative assessment even the need to prioritise across a range of risks is essentially a relative rather than an absolnte judgement. 

The biological monitoring of lead exposure in paediatric and adult human populations has usually involved one of two approaches (1) measurement of the internal or systemic dose of lead itself in some indicator medium, or (2) quantification of some subcritical effect of lead. The extent to which biological monitoring in humans accurately states both exposure risk and relative health risk remains the subject of much research. Of particular interest are (1) the biokinetic characteristics of the common indicators of exposure, (2) the development and use of kinetic models of lead metabolism, and (3) the relative merits of the use of biological effect indicators versus measurement of the toxicant in some medium. 

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