Basic principles for choosing numerical criteria at the safety function level

Safety assessment criteria are generally specific to the industry or activity to which they are applied. The traditional approach to determine appropriate reliability levels is based on the experience. This approach is clearly inadequate when considering the protection required against rare events. In order to avoid the deficiencies of an arbitrary or ad hoc approach, criteria at the safety function level should be related to rational overall safety objectives. The relationship to criteria at the human safety level is explored in this paper, followed by a discussion of the implications of using human safety criteria for this purpose. (author)