1 (ed. C. Klüppelberg, D. Straub, and I.M. Welpe), 3–35. Heidelberg: Springer‐Verlag.
Note
1 1 System aspects are discussed in Chapter 4.
Chapter 2 The Words of Risk Analysis
2.1 Introduction
In 1996, the prominent risk researcher Stan Kaplan received the Distinguished Award from the Society for Risk Analysis. To express his gratitude, Kaplan gave a talk to the plenary session at the society's annual meeting. In the introduction to this talk, he said:
The words of risk analysis have been, and continue to be a problem. Many of you remember that when our Society for Risk Analysis was brand new, one of the first things it did was to establish a committee to define the word “risk.” This committee labored for 4 years and then gave up, saying in its final report, that maybe it's better not to define risk. Let each author define it in his own way, only please each should explain clearly what way that is (Kaplan 1997 , p. 407).
This quotation neatly summarizes one of the problems with this discipline; there are no common definitions of many of the words that we are using. One reason may be that risk is a concept that many disciplines are concerned about, bringing different starting points, perspectives, and terminologies into the discussion. In addition, risk is a term that is commonly used in everyday language, often without a precise meaning attached to it. This chapter attempts to define the key concepts and words from the point of view of the main objectives of this book, which is risk assessment of technical and sociotechnical systems. This means that other users of risk analysis and risk assessment may choose other definitions, and we briefly mention some of these in this section. We have tried to develop a coherent and useful set of definitions that fits our purpose.
A word of caution when reading about this topic is, therefore, to make sure that you understand what the authors mean, when they use words such as risk, hazard, and accident. Unfortunately, not all authors writing about risk have heeded the advice of Stan Kaplan, explaining clearly how they define the terms. The meaning may therefore be unclear and different from how we define the terms in this book.
When discussing risk and other terms in this chapter, we sometimes use terms before they are properly defined. If this causes confusion or things are unclear, please be patient and read on and things will hopefully become more clear as you progress through the chapter.
2.2 Risk
Bernstein (1998) claims that the word risk entered the English language in the 1660s from the Italian word risicare, which means “to dare.” This tells us something about what risk may mean, but if you ask ten people about the word risk, you most likely get ten different answers. The same inconsistency prevails in newspapers and other media. A search for the word risk in some Internet newspapers gave the results in Table 2.1 .
Table 2.1 The word risk as used in some Internet newspapers (in 2018).
| Ford recalls electric car power cables due to fire risk.Is financial turmoil in Turkey and other emerging economies at risk of spreading?Are there any other legal risks?Investors are willing to take on a high risk.Bridge designer warned of risk of corrosion.Saturday features more widespread rain risk.Multigene test may find risk for heart disease.We could put at risk our food and water supplies.This political risk was described in an intriguing analysis.Because of the risk of theft. | Reindeer at risk of starvation after summer drought.Coalition at risk as talks on refugee policy falter.Seven ways to minimize the risk of having a stroke.Company to close 42 stores, putting 1500 jobs at risk.Death is a risk the drivers willingly take and their loved ones accept.You are putting lives at risk over Brexit.This carries an accident risk of “Chernobyl proportions.”£ 80 billion investment plan at risk. |
In some of the statements, the word “risk” may be replaced with chance, likelihood, or possibility. In other cases, it may be synonymous with hazard, threat, or danger. The situation is not much better in the scientific community, where the interpretation is almost as varying as among the general public. A brief search in risk assessment textbooks, journal articles, standards, and guidelines easily prove that this applies also for the specialists in risk assessment.
2.2.1 Three Main Questions
Risk (as used in this book) is always related to what can happen in the future. In contrast to our ancestors, who believed that the future was determined solely by the acts of God (e.g. see Bernstein 1998), or by destiny, we have the conviction that we can influence the future by analyzing and managing risk in a rational way. Our tool is risk assessment, and our goal is to inform decision‐making concerning the future.
The possibility that events with unwanted effects may happen is an inherent part of life. Such events can be caused by natural forces, such as flooding, earthquake, or lightning; technical failures; or human actions. Some events can be foreseen and readily addressed, whereas others come unexpectedly because they appear unforeseeable or have only a very remote likelihood of occurrence. In many systems, various safeguards are put in place to prevent harmful events or to mitigate the consequences should such events occur. Risk assessment is used to identify what harmful events can occur, the causes of these events, to determine the possible consequences of harmful events, to identify and prioritize means to reduce risk, and to form a basis for deciding whether or not the risk related to a system is tolerable.1
For the purpose of this book, we follow Kaplan and Garrick (1981) and define risk as:
Definition 2.1 (Risk)
The combined answer to the three questions: (1) What can go wrong? (2) What is the likelihood of that happening? and (3) What are the consequences?
The three questions may be explained briefly as follows2 :
1 (1) What can go wrong?To answer this question, we must identify the possible accident scenarios that may harm some assets that we want to keep and protect. An accident scenario is a sequence of events, starting with an initiating event and ending with an end state that affects and causes harm to the assets. The assets may include people, animals, the environment, buildings, technical installations, infrastructure, cultural heritage, reputation, information, data, and many more.
2 (2) What is the likelihood of that happening?The answer to this question can be given as a qualitative statement or quantitatively as probabilities or frequencies. We consider each accident scenario that was identified in Question 1, one‐by‐one. To determine the likelihood, it is often necessary to carry out a causal analysis to identify the basic causes (hazards and threats) that may give rise to the accident scenario.
3 (3) What are the consequences?For each accident scenario, we must identify the potential harm or adverse consequences to the assets mentioned in Question 1. Most systems have safeguards or barriers that may prevent or mitigate harm. The harm to the assets depends on whether or not these barriers function as required when the accident scenario occurs.
A
