Table 1

Summarising the interactions between reactive and proactive measures

Type of navigational aid
Reactive measuresProactive measures
Local and organisational conditionsAnalysis of many incidents can reveal recurrent patterns of cause and effectIdentify those conditions most needing correction, leading to steady gains in resistance or fitness
Defences, barriers and safeguardsEach event shows a partial or complete trajectory through the defencesRegular checks reveal where holes exist now and where they are most likely to appear next