## 6 Risk Evaluation  
The risk evaluation applies the event tree for the collision event. The basic structure of the event tree is based on the MEPC report [31] and is used for the calculation of PLP. The assumption of property loss is based on Table 6 and the event tree for a collision is presented in Figure 13. Values in Table 6 are based on a total loss of a new ship, in this case a Panamax size, and divided in bands according to a damage extent. The similar approach was used in the IMO Formal Safety Assessment [23].  
The main branches of the collision event tree have four main levels. At the first, the ship is considered as moored or sailing (stuck or striking), the second is the area of the accident (terminal area, congested waters, open waters, or limited waters), the third is the loading condition (loaded or in ballast), and next is the accident magnitude where the hull could be breached or not. Double hull penetration or single hull ship type are also considered. The probability of each branch is partially obtained from the MEPC report but modified with the statistical data from the Port of Koper and the police port. The initial collision probabilities for two ports have been previously calculated in paragraph 3 and used in the event tree. The final probabilities of each branch and the risk are calculated and further used for the design of the risk curve. The collision risk is here presented with the F-N curve for a panamax ship. The PLP risk for larger ships could exceed the tolerable risk mainly because of the higher ship value, which is why the average ship size is considered.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Panamax** & **\% Damage Extent** \\ \hline
**Property** & \\ \hline -\(\,\upepsilon\) & 0.00\% \\
74,193.00 \(\upepsilon\) & 0.10\% \\
185,484.00 \(\upepsilon\) & 0.25\% \\
370,968.00 \(\upepsilon\) & 0.50\% \\
741,937.00 \(\upepsilon\) & 1.00\% \\
1,854,843.00 \(\upepsilon\) & 2.50\% \\
3,709,687.00 \(\upepsilon\) & 5.00\% \\
11,129,062.00 \(\upepsilon\) & 1.00\% \\
18,548,437.00 \(\upepsilon\) & 2.00\% \\
22,258,125.00 \(\upepsilon\) & 30.00\% \\
37,096,875.00 \(\upepsilon\) & 50.00\% \\
51,935,625.00 \(\upepsilon\) & 70.00\% \\
74,193,750.00 \(\upepsilon\) & 100.00\% \\ \hline \hline \end{tabular}
\end{table}
Table 6: Ship size characteristics and consequence bands for Panamax ship size.  
Figure 14 shows the economic aspect of the risk where the PLP graph above shows that the property losses, due to collision accidents, do not produce relevant economic risk to the port. It should be noted that risks should be considered together, especially those which are directly related with the cost benefit. The second is the risk curve for the police port that is lower than the Port of Koper only because the initial probability is lower than that calculated for the Port of Koper. Considering that the probability of mooring failure during the collision in port influences the risk curve in the range of 0.1 to 10 M EUR damage, the findings mean that the mooring break of a ship should be considered in the risk assessment, although in the analysed port the risk in both cases is within the acceptable area. The presented results quantitatively suggest the importance of a proper mooring arrangement assuming the probability of a collision in a terminal area.  
Considering the findings from Section 5, the approaching speed to a terminal basin should be about 2 to 3 knots and the approaching angle towards a moored ship not more than 30\({}^{\circ}\). Exceeding these values, the moored ship would break the mooring ropes and move from its mooring position. The F-N curve where the mooring failure is not considered shows that the accident with the same probability  
Figure 14: Collective risk level for an average ship size in port for collision event.  
Figure 13: Ship collision event tree (part).  
of collision could result in property loss that is 8 M EUR higher than when the mooring failure is considered.