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Multi-Factor Causal Chain
Any accident can be seen as a chain of events, one link or event logically tied to the next. An accident is the result of a series of events overloading the chain. Many of the factors may well have been present in the system for some time. In the case of a ship, the links may extend to the time of its design. It includes the ship’s operation over many years, during which unsafe procedures may have been adopted or management decisions have been taken, which adversely affected the vessel in the given conditions at the time of the accident.
Links before the casualty are those acts of omission or commission by those on the ship at the time of the incident. Following the incident, there is a period when the vessel recovers from the situation (it refloats after the grounding, the fire is put out, etc.) – or the ship is lost. Since an accident is the result of a series of events, concentrating on only one element during the investigation may result in overlooking underlying causal factors.
Herald of Free Enterprise, a Ro-Ro ship which capsized on 6 March 1987.
In the case of the Herald of Free Enterprise, active and latent failures resulted in the capsizing of the vessel. The active failures resulted in not ensuring that the bosun closed the door and the bow door was left open. Examples of possible shortcomings were:
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Management refused to install warning lights for the bow doors.
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Work schedules for officers and crew.
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Hours of work.
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Change in route from the one for which the vessel was designed.
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The need to ballast and deballast to adjust the vessel’s trim.
Case Study: Herald of Free Enterprise Errors
Factors That Create Accidents
There are active and latent errors, which can combine to create accidents. Active errors arise from the interaction of individuals with the system that is being operated and the environment. Active errors can be seen as those actions taken by a ship’s crew immediately before and at the time of the incident.
Latent errors are the result of decisions or conditions at several levels involving design, management procedures, training, maintenance schedules, etc. The nature of latent factors underlines the often artificial distinction between ship/mechanical failures and human elements. It is based on three interrelated levels or conditions of decision-making, “fallible decisions,” “line management deficiencies,” and “psychological precursors.”
Organisation flow chart.