Because several scenarios are considered in the ARAMIS
audit and, therefore, many barriers are involved, a classification
system has been developed to reduce the amount of
barriers to a limited number of categories that supposedly
have common management influences for all members of
one category but different across categories. This classification
system is based on three barrier characteristics: the
main barrier tasks – detect, diagnose and act – the cognitive
effort to carry out these tasks – skill (s), rule (r) or
knowledge (k) based – and whether the barrier has a control
(positioned in fault tree or left-hand side of bow tie)
or safety function (positioned in both fault and event trees).
Thiswould actually result in 3×3×2 = 18 types, but the distinction
between some types is so small that their categories
have been merged. The 11 resulting types are provided in
Table 1