Risk analysis : a tool in decision-making

Abstract: In our daily life we are surrounded by different kind of risks and we constantly strive for better methods to quantify and in the prolongation manage these risks. Every activity involves some risks and there are some kinds of risks and some level of risks that we are unwilling to accept. We all like to live a life that is free from risks, but that is impossible.The word risk has a lot of different interpretations. In this thesis we shall let risk stand for the combination of random or uncertain events with negative consequences for human health, life and welfare and for the environment together with some measures of the likelihood of such events. We believe this is the prevailing concept or understanding of risk; as the probability of an event followed by some negative consequences or activities of that event.In risk analysis one tries to recognize the nature of various risks and to assess the magnitude of the risks. In the risk analysis it is very important to know what system to consider and this is not self evident in many cases. The situation is clearly different for planning and/or building a system compared with running the same system in a real time state. The system that is going to be the subject to the risk analysis must be clearly defined and the limitations and the boundaries of the system must be set. It is very important to ensure that all persons involved in a risk analysis have a common understanding of the system being considered, including relevant operations.During the past decades many studies have been carried out on risk related topics and the society has showed a significant interest in the field of risk analysis. Risk analysis is the interdisciplinary field of science that combines results and knowledge of probability theory, mathematical statistics, engineering, medicine, philosophy, psychology, economics and other applied disciplines.In this thesis we will give some examples of different risk analyses carried out basically within two areas. The first part of the thesis (paper 1- paper V) describes different risk analyses carried out in the area of transportation. This is an area with large differences between the different modes of transportation in respect to, for example number of users, number of accidents, magnitude of the accidents and accessible data. The latter part of the thesis (paper VI and paper VII) describes two risk analyses carried out in the field of medicine. Medicine is a science, which has used methods from the area of risk analysis for a long time. The different papers will be used to discuss risk analysis as a tool in decision-making.