Modelling the impact of human fatigue on the risk of shipping accidents

Human fatigue is influencing the risk of maritime accidents. A ship`s bridge sailing in trafficked waters is a multi-causal and complex system. Decisions made on the bridge may have invisible and delayed consequences. This article explains how and why accident investigation reports can be used to construct easily updateable quantitative risk assessment models which take human factors into account. The article then makes use of the Barrier and Operational Risk Analysis (BORA) method to illustrate an example by conducting a case study of the effect of human fatigue on maritime groundings. The case study indicates that lowering the probability of human fatigue and alcohol misuse on board does not decrease the probability of grounding as much as lowering the probability of barrier failures (lookouts, watch alarms and VTS radio calls). Less than adequate scores on human fatigue, safety climate and manning levels have a stronger effect on the probability of grounding then adequate scores.