basis and only adds to the societal consequences of such event. To the extent possible such
behaviour should be included in the consequence assessment as a follow-up consequence.
Due to the effects of the perception of risk it is generally observed that different individuals
and groups of individuals have different attitudes in regard to what risks can be accepted,
moreover this attitude to high degree is affected by the characteristics of the associated
adverse events. Risk averse and risk prone attitudes are observed which simply refers to the
effect that risks are assigned different tastes depending on these characteristics. Whereas such
behaviour is a private matter for individuals of society it leads to an uneven distribution of
risks if exercised in the context of societal decision making and this is clearly unethical and
from that perspective also not rational.
The perception of risks may be significantly influenced by information about the risks
themselves. Being provided with transparent information in regard to the nature of exposures,
possible precautionary actions, information on how risks are being managed and the societal
consequences of irrational behaviour reduces uncertainties associated with the understanding
of risks of individuals. This in turn adds to rational behaviour and thereby reduces follow-up
consequences. For this reason schemes for targeted, transparent and objective information of
the stakeholders is a highly valuable means of risk treatment.
4.5 The Procedure of Risk Assessment
The individual aspects of risk assessment as outlined in section 4.4 may be realized to be of a
generic nature in the sense that they apply for any type of engineered facility or activity. In
Figure 4.9 a flow chart for a risk assessment procedure is illustrated. It is seen that the aspects
of risk assessment discussed in section 4.4 may all be allocated to the different activity boxes
of the flow chart. The “definition of the context” box concerns the identification of the
decision maker, the constraints of the decision making and the thorough understanding and
representation of the preferences of the decision maker. The “system definition” box relates to
the representation of the system. Here the main issue is to identify which exposures and
consequences (direct and indirect) will be included in the risk assessment. The “identification
of hazard scenarios” box concerns the understanding and modelling of the causal or logical
interrelations between events which initiating with an exposure event may lead to direct and
indirect consequences. In the boxes concerning “analysis of probabilities” and “analysis of
consequences” the components needed to quantify risk are analysed, i.e. probabilities of
consequence inducing events and their corresponding consequences. Therefore this step in a
risk assessment is also sometimes denoted risk analysis. The step referring to the
“identification of risk scenarios” concerns the ranking of the different hazard scenarios in
accordance with their risk. This facilitates focussing the further analysis on the hazard
scenarios which dominate the risk. The box denoted “sensitivity analysis” refers to an
evaluation of whether a refinement of the modelling of scenarios is required. Typically this
activity is directed on the evaluation of the significance of assumptions made in the course of
the system representation. If the results regarding the quantified risks are very sensitive to
modelling assumptions usually a refinement of the system representation is necessary. Under