What is “safety” and is there “optimal safety” in engineering?

In this section a definition of the term “safety” based on freedom of resources is introduced. Such freedom of resources can also be used for the definition of the terms “danger” and “disaster”. Additionally, the terms “safety”, “danger” and “disaster” can be correlated to time horizons of planning. The introduced relationships will then be used for the discussion whether “optimal safety” is achievable or not. Currently, “optimal safety” is being intensively discussed in many disciplines such as the field of structural safety. Considering the definition of “safety”, this paper will show that “optimal safety” is rather a theoretical issue and cannot be achieved under real world conditions. This statement fits very well not only to considerations in the field of system theory, but also to empirical observations. It is suggested that the term “optimal safety” is introduced as an assurance measure for engineers rather than for the public. As a solution the concept of integral risk management is introduced. One of the properties of this concept is the possibility of continuous improvement and therefore no optimal solution is claimed.