ABSTRACT
In most high risk systems, standardization in the form of standard operating procedures has been developed with ever increasing detail in order to streamline human action and to reduce its influence as a risk factor. Procedures are often a direct consequence of incidents and accidents, the analysis of which provides knowledge of unforeseen wrongful courses of action against which new rules are developed as a defence. While generally there is an understanding that rules are useful guides for safe behaviour, there is also an increasing concern that too many rules incrementally developed will not make up a good system to help human actors do the right thing, especially in states of abnormal operation where they would need strong, but also flexible guidance (e.g. Amalberti, 1999; Dekker, 2003; Woods & Shattuck, 2000).
