risk analysis is carried out to provide answers to the three questions in the definition of risk. Risk analysis and risk assessment are further defined and discussed in Chapter 3. The first question “what can go wrong?” clearly shows that we focus on scenarios that give “negative” consequences – even if risk refers to both gains and losses in economic theory.
Remark 2.1 (Positive and negative consequences)
Observe that classifying a consequence as positive or negative represents social judgments and cannot be derived from the nature of the accident scenario (Klinke and Renn 2002). This implies that consequences can be regarded as positive by some people and negative by others. Examples include terrorist attacks or other cases where someone wants to cause harm. The terrorists aim to cause as much harm as possible to get attention. For them, it is therefore a positive consequence. For most others, it is seen as negative.
Remark 2.2 (Danger)
The word danger is used in our daily language, both as a noun and as the associated adjective dangerous. Standards for risk assessment very seldom use the noun danger, but the adjective dangerous is commonly used in expressions such as dangerous chemicals, dangerous behavior, and dangerous activity. We follow the standards and refrain from using the noun danger in this book.
2.2.1.1 Expressing Risk
The answer to the first question in Definition 2.1 gives a set of accident scenarios
provides a name, a precise definition, and a description of potential accident scenario
is an estimate of the likelihood (e.g. frequency) of accident scenario
is a multidimensional vector of the potential types of harm/damage to all relevant assets caused by accident scenario , with associated probabilities, that is, the consequence spectrum for
The risk
If all relevant accident scenarios
The risk – defined by answers to the three questions – may be presented as in Table 2.2 , where the first column lists the accident scenarios
Table 2.2 Risk related to a system (example).
|
|
Accident scenario |
Frequency |
Consequence |
| 1 | Gas leak in area 1 | 0.01 | Consequence spectrum 1 |
| 2 | Falling load from crane 2 | 0.03 | Consequence spectrum 2 |
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|
|
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2.2.2 Alternative Definitions of Risk
Many alternative definitions of risk have been suggested in the literature. Among these are the following:
1 (a) “Effect of uncertainty on objectives” (ISO 31000). This definition is different from the one used in this book. Events are not mentioned in the definition and it also encompasses both positive and negative consequences.
2 (b) “The possibility that human actions or events lead to consequences
