Constructing these CPTs requires a discretization of variables m1, m2, v1, v2, φ, l, η, x1, x2, x3 and x4, as defined in Section 5, which is done with a resolution as given in Table 6. These are mapped onto the respective discrete
classes of the variables θ, yL and yL, discretized as outlined in Section 4.4.1. This is done by random sampling of 100 cases from the ranges of the parent variables of and determining the probability of the resulting value of the child variable, as calculated through Eqs. (14), (15), (16), (17), (18), (19), (20), (21), (22), (23) and (24), falling in each of its discrete classes. The resulting BN model for cargo oil outflow of product tankers conditional to given impact scenarios is shown in Fig. 7. The variables describing the impact scenario are v1, v2, φ, l, m1 and Selleckchem Alpelisib m2, located in the top and left check details part of the model. The variables describing the tanker design are grouped in the right part of the model, i.e. variables L, B, DWT, Displ, TT, ST, CT. The central part of the model contains the variables linking the impact scenario with the damage extent and
ultimately the oil outflow. To illustrate the utility and outcome of the model, two realistic scenarios relevant in risk assessment in the Gulf of Finland area are considered. In the first scenario, a fully laden medium-size product tanker sailing at normal operating speed is struck by a RoPax vessel also sailing at normal operating speed. Such a scenario may occur in the TSS area5 in the crossing area between Helsinki and Tallinn, see Fig. 8. In the second scenario, a fully laden medium/large-size product tanker sailing at normal operating speed is struck by a fully laden Suezmax tanker also Fossariinae sailing at normal operating speed. Such a scenario may occur in the TSS area off Kilpilahti,
where product tankers encounter crude oil tankers sailing on the east–west route, see Fig. 8. With this information, the relevant vessel particulars and impact speeds can be estimated as shown in Table 7. There is however significant uncertainty regarding other impact scenario variables such as the relative impact location l and impact angle φ, as the process from encounter to impact conditions is not well understood ( Ståhlberg et al., 2013). To show the effect of these variables, two sets of analyses are shown, where these uncertain variables are systematically varied, see Fig. 9. In the preceding sections, the general framework for the BN construction was outlined and the various steps in the construction of the probabilistic oil outflow model were presented in more detail. The validity of the oil outflow model in light of the intended application area and the adopted risk perspective is discussed in more detail in this Section.