Über die Autorin bzw. den Autor

Terje Aven is Professor of risk analysis and risk management at the University of Stavanger, and a Principle Researcher at the International Research Institute of Stavanger (IRIS). Having worked in both industry and academia, he has participated in, and led, many safety and risk related projects, winning several awards for both research and teaching. He has published numerous papers in international journals, and has authored several books.

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Everyday we face decisions that carry an element of risk and uncertainty. The ability to analyze, predict, and prepare for the level of risk entailed by these decisions is, therefore, one of the most constant and vital skills needed for analysts, scientists and managers.

Risk analysis can be defined as a systematic use of information to identify hazards, threats and opportunities, as well as their causes and consequences, and then express risk. In order to successfully develop such a systematic use of information, those analyzing the risk need to understand the fundamental concepts of risk analysis and be proficient in a variety of methods and techniques. Risk Analysis adopts a practical, predictive approach and guides the reader through a number of applications.

• Provides an accessible and concise guide to performing risk analysis in a wide variety of fields, with minimal prior knowledge required.
• Adopts a broad perspective on risk, with focus on predictions and highlighting uncertainties beyond expected values and probabilities, allowing a more flexible approach than traditional statistical analysis.
• Acknowledges that expected values and probabilities could produce poor predictions - surprises may occur.
• Emphasizes the planning and use of risk analyses, rather than just the risk analysis methods and techniques, including the statistical analysis tools.
• Features many real-life case studies from a variety of applications and practical industry problems, including areas such as security, business and economy, transport, oil & gas and ICT (Information and Communication Technology).
• Forms an ideal companion volume to Aven’s previous Wiley text Foundations of Risk Analysis.

Professor Aven’s previous book Foundations of Risk Analysis presented and discussed several risk analysis approaches and recommended a predictive approach. This new text expands upon this predictive approach, exploring further the risk analysis principles, concepts, methods and models in an applied format. This book provides a useful and practical guide to decision-making, aimed at professionals within the risk analysis and risk management field.

Aus dem Klappentext

Everyday we face decisions that carry an element of risk and uncertainty. The ability to analyze, predict, and prepare for the level of risk entailed by these decisions is, therefore, one of the most constant and vital skills needed for analysts, scientists and managers.
 
Risk analysis can be defined as a systematic use of information to identify hazards, threats and opportunities, as well as their causes and consequences, and then express risk. In order to successfully develop such a systematic use of information, those analyzing the risk need to understand the fundamental concepts of risk analysis and be proficient in a variety of methods and techniques. Risk Analysis adopts a practical, predictive approach and guides the reader through a number of applications.
 
* Provides an accessible and concise guide to performing risk analysis in a wide variety of fields, with minimal prior knowledge required.
* Adopts a broad perspective on risk, with focus on predictions and highlighting uncertainties beyond expected values and probabilities, allowing a more flexible approach than traditional statistical analysis.
* Acknowledges that expected values and probabilities could produce poor predictions - surprises may occur.
* Emphasizes the planning and use of risk analyses, rather than just the risk analysis methods and techniques, including the statistical analysis tools.
* Features many real-life case studies from a variety of applications and practical industry problems, including areas such as security, business and economy, transport, oil & gas and ICT (Information and Communication Technology).
* Forms an ideal companion volume to Aven's previous Wiley text Foundations of Risk Analysis.
 

Professor Aven's previous book Foundations of Risk Analysis presented and discussed several risk analysis approaches and recommended a predictive approach. This new text expands upon this predictive approach, exploring further the risk analysis principles, concepts, methods and models in an applied format. This book provides a useful and practical guide to decision-making, aimed at professionals within the risk analysis and risk management field.

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Risk Analysis

John Wiley & Sons

Chapter One

This chapter presents a selection of methods that can be used when carrying out a risk analysis. These methods are described in detail in the literature and in a number of textbooks within this professional field (Modarres 1993, Rausand and Hyland 2004, Bedford and Cooke 2001, Vose 2000, to mention a few). In this book, we present a short summary of the most fundamental methods, partly based on Aven (1992).

6.1 Coarse risk analysis

A coarse risk analysis (often also referred to as a preliminary risk analysis) is a common method for establishing a crude risk picture, with relatively modest effort. The analysis covers selected parts of, or the entire, bow-tie (see Figure 1.1), i.e. the initiating events, the cause analysis and the consequence analysis. The analysis team typically consists of 3-10 persons.

Often the coarse risk analysis is performed by dividing the analysis subject into sub-elements and then carrying out the risk analysis for each of these sub-elements in turn. This applies regardless of whether the analysis focuses on a section of a highway, a production system, an offshore installation or other analysis subjects. Checklists may be used as a tool for identifying and analysing hazards and threats for each sub-element to be analysed.

The form used to document the risk analysis is often standardised. An example of an analysis form for a risk analysis of a road tunnel is shown in Table 6.1. We see from the table that the risk is described by using categories. The categories cover possible undesirable events, along with the probability and expected consequence if such an event should occur. We see from the table that, in the case of a bus fire, we expect that there will be 10 people killed. The number can be 0, 1 or 30, but the expectation is 10.

In stating probabilities, terms such as often and seldom should be avoided as they are open to different interpretations. A better alternative is to say directly what we mean, for example, 10-50% probability that an event will occur within the period of 1 year. Some people will perhaps say that it is difficult for the analysis group to express that there is a 1-10% probability or a 10-50% probability, for example. The answer to this is "yes," it can be difficult to assign probabilities. However, it does not help "hiding" behind expressions such as "often" or "seldom" without explaining what one means by these terms. Also, the consequence categories should be precisely defined, rather than using terms such as high, low, etc.

A coarse risk analysis is often combined with other analysis methods. The coarse analysis identifies the most important risk contributors, and then the causal picture and/or the consequence picture can be assessed in detail using more detailed analyses.

Example: workplace accidents

The working environment committee at the Packing Factory Ltd has found that in the bag department, which has about 90 employees, the number of injuries is too high. The committee therefore decides to implement some injury preventive measures to reduce the injury rate in the department. It is, however, not clear where such measures should be directed and which measures would most effectively prevent injuries. Opinions in the working environment committee differ widely.

In the bag department, production is a series production of large, multiple-ply paper bags. Each production line comprises several machines. The raw material is paper rolls. The main operator task in the department is to monitor and adjust the machines. Some operators deal with manual handling of products. It is the operators who are operating the machines that are most exposed to injuries.

The working environment committee instructs the safety delegate of the company to work out a basis for decisions on preventing measures. The safety delegate is familiar with risk analyses and he uses such an analysis to establish the desired decision basis.

By means of the risk analysis, the safety delegate will identify possible injuries that might occur in the department, where they might occur, possible causes and the severity of the injuries. Table 6.2 presents a summary of the analysed hazards. With respect to probability/frequency, the following classification is used:

1. very unlikely: less than once per 1000 years (yearly probability 1:1000);

2. unlikely: once per 100 years (yearly probability 1:100);

3. quite likely: once per 10 years (yearly probability 1:10);

4. likely: once per year;

5. frequently: once per month or more frequently.

Also for the consequences five categories are used:

I does not result in injuries II minor injuries III major injuries

IV death or total disability

V death or total disability for several persons.

The starting point for the hazard identification was the injury reports for the whole department for the last 9 years. Data on near misses were also available. In addition, the system description was studied to identify other hazards. For the hazards based on the injury reports, the classification is based on this statistics. For example, two injuries caused by crushing in the cutting machinery are registered. This gives a classification "likely." Judgement has been used for the hazards that are not based on the injury statistics.

In Figure 6.1 the hazards have been placed in a consequence probability diagram. The consequence categories are marked along the horizontal axis with consequences increasing to the right. Similarly, the frequency/probability is marked along the vertical axis, with frequency increasing downwards. The following conclusions are drawn:

highest risk: hazard number 14, which equals "paper roll falls from tackle;" other contributors to high risk are: events that include crushing and catching in the machinery.

The events with the lowest risk are numbers 9 and 15. Thus, in general, for this type of consequence probability diagram, the events with the highest risk are those in the bottom right corner, whereas the events with the lowest risk are placed in the upper left corner. We should, however, be very careful when drawing conclusions from the matrix since it is based on a rough classification.

Note that hazard 15 (paper fire) has low risk in relation to personnel. If we focus on material assets or economic values, this hazard would contribute much more to risk.

Based on the risk analysis, the safety delegate can now identify and rank measures to prevent accidents, as a basis for the decision-making on which measures to implement.

6.2 Job safety analysis

A job safety analysis is a simple qualitative risk analysis methodology used to identify hazards that are associated with a work assignment that is to be executed. A job safety analysis is usually checklist-based. Normally, the persons planning/executing the work assignment are part of the analysis team. By carrying out a job safety analysis, we ensure:

It is clarified whether the work assignment is a "standard" operation that can be carried out according to procedures and normal practice or if it is a non-standard case that requires special measures or studies. The latter case may...