Risk analyses are widely used tools for supporting decision making. Nonetheless, many criticisms have been raised against the discipline of risk analysis, e.g. technical analyses having a narrow focus, poorly examined claims of the ability of accurately measuring risk and lack of standards for quality assurance and risk analysis evaluation. In response to these criticisms, calls have been made for increased focus on these and other foundational issues, both in the general risk analysis discipline and in the various application areas.

This thesis answers these calls for research addressing the underlying concepts and principles of risk analyses, which are approached through applications focusing on the accidental risk of maritime transportation. Focusing first on a set of foundational issues underlying waterway risk analyses, it is established that many different definitions, perspectives and scientific approaches co-exist in the application area. Through two case studies of reliability of maritime risk models, previous research claiming that risk models provide unreliable decision support, are confirmed for some maritime applications, thus confirming the need for focusing on risk related principles.

Subsequently, a set of principles is presented, addressing concepts and terminology, risk and prediction, risk model use and the consideration of uncertainty and bias. A framework is introduced to communicate the scientific principles adhered to in a specific risk analysis.

Following this, the principles are translated in two risk analysis frameworks:​ one for policy-oriented and one for operational risk analysis;​ the first leading to a quantitative and the second to a qualitative risk characterization. In both, risk is understood as a concept referring to the possible but uncertain occurrence of a situation where something of human value is at stake.

Risk models are used as putting forward an argument based on available evidence, as a tool for communication between stakeholders and as a platform for thinking. Uncertainties and value-laden biases are assessed, and some tools for communicating these are introduced. Both frameworks are illustrated by extensive case studies. The first concerns accidental risk of oil spills from tanker collisions in the Gulf of Finland. The second focuses on a risk-informed shipship collision alert system.

A final issue addressed in the thesis concerns the evaluation of a risk analysis, i.e. principles and criteria for establishing credibility. An integrated framework for this is developed, addressing model use, model plausibility, value-related validity and process-related validity. Specific evaluation criteria are proposed and a selection of these is applied in the presented case studies.