Accident Frequency Analysis for the Stad Ship Tunnel
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- Institutt for marin teknikk 
The objective of this thesis is to find a suitable method to update previous risk analyses on the projected fairways of the Stad Ship tunnel, which is planned to reduce coastal traffic exposure to severe weather in the Stad sea. A previous analysis from 2010 carried out by the DNV utilises accident statistics and vessel exposure data to obtain a frequency of accidents for a tunnel case compared to a no tunnel case. Traffic densities are obtained from observing traffic data. It is decided that a new frequency analysis based on a geometrical model and updated traffic data might improve on the assessment in terms of accuracy. Traffic data is obtained from the Norwegian Coastal Administration, and a program is developed to estimate traffic patterns and vessel parameters to calculate collision and grounding frequencies according to the IWRAP method. This is carried out for the current sea route and the planned tunnel route. It is found that the collision and grounding frequencies for the tunnel route are slightly higher than found in the previous assessment, while frequencies for the sea route were significantly lower. Sensitivity analyses show that the model is particularly sensitive to lane positioning, but also that there is a large potential for expanding the model with more accurate representations of traffic patterns off Stad, which are found to be complex. It is concluded that the model is well suited to the enclosed waters of the Stad tunnel fairways, and that the model is useful in defining critical areas in the fairways, which is an advantage over the method utilised previously. It also allows flexibility and the opportunity to investigate scenarios for different vessels and fairway parameters Further work is suggested to improve the accuracy of the model for open seas. To reach a sufficient level of accuracy for modelling the frequency of collisions and groundings off Stad it is suggested that further research is carried out on meteorological effects on traffic patterns and on a vessel s ability to navigate, which are important factors in quantifying the frequency of accidents for this area.