ABSTRACT
This chapter shows that collecting and analysing small failures is worthwhile and can be used to help prevent more serious accidents and incidents. The assumption of the predictive validity of near misses was first posited by H.W. Heinrich and is generally known as the 'common cause hypothesis'. The use of near misses to aid the decision-making process is based upon the assumption that near misses and more serious accidents have the same underlying causal patterns. Heinrich used his ratio triangle to suggest that a reduction in 'no injury' incidents would lead to a reduction in minor injury incidents and in major injury incidents. The existence of a ratio relationship between major injury accidents, minor injury accidents and 'no injury' accidents says nothing about causation. The chapter illustrates the use of ratio data to test the common cause hypothesis. Proximal causes of events are defined as causes associated with frontline operators.
