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Defence in depth

Additional factors - summary


The criteria address the wider issues of human performance and safety management.

There are three areas that need to be considered: common cause failures, procedural inadequacies and safety culture issues.

To increase the rating, there has to be a real indicator of an issue with the safety culture.

The basic rating can be uprated by a maximum of 1 level.

Care must be taken not to double count.

There is an upper limit to the rating under defence in depth.

An event should be rated at the maximum level only for a 'near miss', i.e. one further failure would have led to consequences for people and the environment.