The role of risk in estimation of safety navigation

The paper presents the method of estimation of safety navigation. The proper criteria, measures and rate will need the estimation of safety navigation. These are very often expressed by risk. Four different definitions are used. The mostly used definition is a combination of accident probability with connection to its results. Probability of accident can be expressed in different manner. Three kinds of them are presented. Also the consequences of accident may be calculated in many aspects. There are necessary activities leading to efforts of unifying of these quantities.