Division 2.2 Calculation

The probability of the potential accident outcome is the numerical value resulting of the following steps:

Step 1: A sum of all the barrier weights (1 to 5) laid down in the table in section 2.1.1 of all the assessed barriers that were scored either ‘Stopped’, ‘Remaining known’ or ‘Remaining assumed’. The ‘Failed’ and ‘Not Applicable’ barriers shall not be counted for the final score, as those barriers could not have prevented the accident. The resulting barrier weight sum is a numerical value between 0 and 18.

Step 2: The barrier weight sum corresponds to a barrier score between 0 and 9 as per the following table, covering the full range between strong and weak remaining barriers.