Marvin Rausand - Risk Assessment

3 (3) Third‐party victims. These are innocent bystanders who have no involvement in the system, for example, people living in the neighborhood of a plant.

4 (4) Fourth‐party victims. These are victims of yet‐unborn generations. The category includes fetuses that are carried while their parents are exposed to radiation or toxic materials, and all those people who will be contaminated in the future by residual substances, including substances that become concentrated as they move up the food chain.

The railway industry sometimes classifies human assets in five categories:

1 (a)Passengers

2 (b)Employees

3 (c)People on the road or footpath crossings of the line

4 (d)Trespassers (who are close to the line without permission)

5 (e)Other persons

In addition to distinguishing between different assets, the adverse effects may also be classified into several categories related to the assets. Some examples are given in Table 2.7.

Table 2.7Some types of harm to different assets.

For harm to people, it is common to distinguish between:

1 – Temporary harm/injury. In this case the person is injured but will be totally restored and able to work within a period after the accident.

2 – Permanent disability. In this case, the person gets permanent illness or disability. The degree of disability is sometimes given as a percentage.

3 – Fatality. The person dies, either immediately or because of complications. The fatality may sometimes occur a long time after the accident, for example, due to cancer caused by radiation after a nuclear accident.

A hazardous event (or end state) may lead to a number of potential consequences , , …, . The probability that consequence will occur depends on the physical situation and whether or not the barriers are functioning. The possible consequences and the associated probabilities resulting from the hazardous event are shown in Figure 2.5.

Figure 2.5Consequence spectrum for a hazardous event.

The diagram in Figure 2.5is called a consequence spectrum , a risk picture , or a risk profile related to hazardous event . The consequence spectrum may also be written as a vector:

(2.8)

In Figure 2.5and in the vector ( 2.8), we have tacitly assumed that the consequences can be classified into a finite number ( ) of discrete consequences. This is often a simplification that we make in risk analysis.

A study object may lead to several potential hazardous events. It may therefore be relevant to establish the consequence spectrum for the study object rather than for a single hazardous event. Each hazardous event then has a consequence spectrum, as shown in Figure 2.5. Combining the consequence spectra for all the relevant hazardous events yields the consequence spectrum for the study object. This consequence spectrum has the same form as for a hazardous event. The consequence spectrum may also be presented in a table, as shown in Table 2.8.

Table 2.8Consequence spectrum for a study object (example).

	Consequence	Probability
1	Operator is killed	0.001
2	Operator is permanently disabled	0.004
3	Operator is temporarily injured	0.008
m	Minor material damage	0.450

The probability associated with each consequence lies between 0 and 1, where means that the consequence is impossible and signals that it will always occur. Both extremities correspond to a fatalistic world view in which the future is conceived of as independent of human activities. According to Rosa (1998), the term risk would be of no use in such a world of predetermined outcomes. At the heart of the concept of risk is thus the idea that the consequences admit to some degree of uncertainty.

In some cases, it may be possible to measure the consequences of a hazardous event to the different assets in a common unit (e.g. in US dollars). Let denote the loss in dollars if consequence occurs, for . The loss spectrum for the hazardous event can then be pictured as in Figure 2.6.