## 2 Risk Assessment Framework  
Several methods of maritime risk analysis dedicated mostly to coastal and open sea areas have been developed [16; 17; 18; 19]. The general risk assessment framework of dangerous cargo terminals located in the vicinity of waterways in respect to possible collision is presented in Figure 2. The overall framework of formal risk assessment for shipping in coastal and open seawaters is presented by [20]. However, in the port area, several differences are observed. Firstly, in port areas, impacts are both generally minor and more likely. Secondly, there are human populations in the port areas that may be threatened by toxic substances released during a collision. The navigation process is also different--usually there are several persons on the bridge performing overlapping tasks (pilot, captain, OOW--officer on watch). The Vanem framework classifies the collision with a moored ship accident as one which could lead to misunderstandings, especially when analysing the causes of accidents. The proposed multi-stage procedure requires applying the following five sub methods:  
1. Expert's method for identification scenario of toxic substance release,
2. Real- or fast-time simulation modelling to find the geometry of collision and highest possible speed of the moving ship,
3. Mathematical models of external and internal ship dynamics,
4. Model of pollution dispersion,
5. Model of consequence to humans, including passengers with consideration of exposure to the chemicals. Figure 1: View of two collision events in a port area, Swinoujscie terminal (**left**) and Port of Koper (**right**). The consequence of the concept applied in this study is related to the accident energy released and with the depth of the moored ship hull penetration. In the presented cases, there is a safety barrier: the ballast tank located on the ship's side denoted by \(d_{b}\). For the purpose of this study, when the potentially catastrophic scenario is taken into account, the risk is calculated as a product of probability and consequences only when the depth of penetration could reach a tank with fuel. Acceptable risk is not specified in Polish or Slovenian legislation for such maritime systems [8; 21]. Moreover, there is not enough operation time of such vessels in the studied area to develop acceptable risk standards based on statistical data as described by [PERSON] [11]. The risk acceptance criteria are therefore calculated based on the potential loss of property [22]. The risk of losing part or all of the port revenue and costs of ship damage or total loss is an economic risk that primarily influences the company policy. The world fleet statistics show that the number of accidents is increasing with the increase in the number of ships sailing. On the other hand, the consequences of accidents are less severe thanks to the continuous maritime standards improvements for ship construction, electronic navigation control, shore vessel traffic services, and more. The risk of property loss is here calculated as:  
\[PLP_{A}=r_{p}\times EV, \tag{1}\]  
where \(EV\) is the average revenue of the port per ship year and \(r_{P}\) is the loss of property for accidents per average port revenue per year. \[r_{P}=\big{(}C_{a\_c}/rev_{a\_y}\big{)}, \tag{2}\]  
where \(C_{a\_c}\) is the average collision cost per ship year and \(rev_{a\_y}\) the average revenue of the port per year. The unit for \(PLP_{A}\) is the ratio of property loss in M EUR/ship year M EUR business economic value. Further, the frequency of property loss is calculated with Equation (3), where \(N_{u}\) is the cost of a total loss depending on ship type. An average value of \(\sum_{N=1}^{Nu}\frac{1}{N}\) for Panamax size is 4.5, where \(N\) is 1 to the maximum property loss in M EUR [23]. \[F=\frac{PLP_{A}}{\sum_{N=1}^{Nu}\frac{1}{N}}\, \tag{3}\]  
Figure 2: Risk assessment framework for moving ship colliding with moored tanker applied in this study. For the year 2018, the tolerable damage cost \(F\) is calculated as \(1.34\times 10^{-3}\) property lost M EUR/ship year.