The Effects of Human Fatigue on Risk at Sea
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- Institutt for marin teknikk 
The main purpose of this PhD thesis is to improve the current international knowledge pool regarding the circumstances in which human fatigue develops on board a vessel and its effect on the probability of maritime grounding accidents. The work focuses on personnel on the ship`s bridge and maritime groundings, however, the methods developed and the techniques shown are relevant to other type of accidents and crews. The thesis reviews the literature on risk modelling, and presents current available methods for developing socio-technical models. The research identifies current challenges for including organisational and human factors in a risk model. In doing so, important fatigue related factors are identified and quantitative links between fatigue and the probability of groundings are shown. The main contributions of this thesis are: - Providing an overview of knowledge gaps and challenges in modelling human fatigue in risk models - Development of four models for assessing human fatigue at sea A Bayesian network model CREAM model Regression model BORA model - Identification of factors that influence human fatigue - Assessment of maritime transport stakeholder views on human fatigue - Identification of ways to improve collection and reporting of data from accident investigation for the purposes of better assessing the contribution of Human and Organizational Factors (HOF) The classical Newtonian view of the world, where the system is understood by dividing it into smaller parts and assigning causal links, does not embody human behaviour adequately. A more systemic view, where the complexity and interaction between dependent variables are recognised, is a preferable approach. This thesis suggests Bayesian Networking (BN) as a convenient tool for modelling socio-technical systems. BN allows one to take into account the many interactions in complex systems. It also allows reasoning in both directions. The BN model developed in this thesis (Article II) indicates that a bridge management team where at least one member of it is fatigued, has a strong negative effect on the probability of grounding. Although Article II does not claim any “true numbers” for probability of grounding or the probability of any of the fatigue related factors included in the model, the BN model still gives valuable information about the relative changes and relations. Fatigue in bridge personnel increased the probability of grounding with 16%. The marginal probability of having a fatigued bridge management team in a random ship is conservatively calculated to be 23%. The stepwise method for building BN introduced in the thesis is transferable to other transport modes. In short, the method uses accident investigation reports to generate Human and Organizational Factor (HOF) data. The HOFs are then structured using a taxonomy (HFACS in our case) and finally a BN is made. The maritime transport sector (MTS) is concerned about high human fatigue levels among seafarers. High human fatigue levels are linked with raised probabilities of less than adequate human performance, of which the consequences may be great, e.g. groundings, collisions and oil spills. It has not been uncommon that accidents occur when officers are in a fatigued state. Proper psychological functioning of seafarers is crucial for the overall safety and reliability of ships. The research in this thesis indicates that the various stakeholders appreciate the importance of having a non-fatigued crew, however, at the same time their perception is that anti-fatigue measures cost more than they generate in benefits. This report of the stakeholders’ belief may be an indication of lack of interest and motivation to implement fatigue reducing measures on board. The belief that fatigue measures are non-effective could have an important part to play. The thesis concludes that the most important fatigue related factors are: Efficiency pressure, LTA (Less than adequate) Manning, Shift scheme of 12 hours on duty followed by 12 hours off, assuming adequate manning (12-12), LTA BRM (Bridge Resource Management) application, LTA Quality control and Variable working conditions. The research conducted in this thesis has been limited to large ships having a minimum of seven crew members (except of article I, where the minimum crew members were set to four) on a voyage lasting at least one day or more. The limitation was used because it was assumed that the circumstances in which fatigue occurring in these ships are basically different from that in other types of ships, for instance fishing vessels or supply ships. The conclusions regarding the effects of fatigue on the probability of grounding can therefore not be generalised without constraints. Different taxonomies and structures exist today for structuring the HOFs. Most taxonomies available are developed with the nuclear or aviation industry in mind. The maritime transport system is different and should therefore have its own specially tailored and reviewed taxonomies of HOFs. This is an important work for the future. The research has also limited itself to looking at fatigue`s effect on accidents. Human performance in post -accident events, given a fatigued state has not been looked into. Limiting damage is an important part of an overall risk analysis. Further work should also devolve into that phase, i.e., the influence of HOF in postaccident scenarios.