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 (Rausand and Høyland 2004, Bedford and Cooke 2001, Vose 2008, 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 a relatively modest effort. The analysis covers selected parts of, or the entire, bow-tie (see Figure 1.1), that is, 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 by 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 ...