# Incorporating Epistemic Uncertainties in Ship Operability Study
## 4 Discussion
### Limitations of the Model  
This study focuses on a single ship model, specifically a passenger ferry operating on a key and frequent route in the Adriatic Sea. This route is significant due to its high frequency of use and delays attract public attention, as discussed in Section 4.3. Another reason for selecting this route is that the environmental conditions along the route are well-defined [24]. For shipping routes in general, considerable uncertainty in environmental descriptions should be included in the limit state equations discussed in Section 2.3.  
Figure 8: Significant wave height in the Adriatic Sea on 24 December 2024 (generated using E.U. Copernicus Marine Service Information [46]).  
Figure 9: Significant wave height along the route Ancona–Split from January 1985 to May 2023 (generated using E.U. Copernicus Marine Service Information).  
One simplification applied in this study is the use of a single-parameter JONSWAP-type wave spectrum for the Adriatic Sea [30]. Although this formulation provides a reasonable approximation for many fully developed wind-generated sea states in the Adriatic, the variation of peak wave periods (_Tp_) with significant wave heights (_H\({}_{S}\)_) should be considered. Particularly, if other wave environments, such as the North Sea or open oceans, are considered, the operability plots should be extended for different combinations of _H\({}_{S}\)_ and _Tp_, as well as for other wave spectral models.  
Although this study can be extended to other ship types, the careful consideration of ship-specific uncertainties in the ship response, heavy weather maneuvering, seakeeping criteria, and limiting values should be conducted. These additional considerations limit the generalizability of this study's conclusions to other vessel types.  
This study does not consider wind effects, although strong winds, including cross-winds or headwinds, can influence ship maneuverability. It is important to note that maritime disasters have occurred due to wind effects in addition to the wave action. In the Adriatic, however, the strongest winds and highest waves do not occur simultaneously [24]. Extreme wind speeds are recorded during the northeastern 'bura' wind, which blows across the shorter axis of the Adriatic basin and generally lasts for a short duration. Despite being the strongest wind, the 'bura' does not generate the highest waves because of the limited fetch. In contrast, the southeastern '**jugo' winds** blow with a lower intensity but are more persistent and have a longer fetch, generating the highest waves in the Adriatic [24].  
As a result, the 'bura' wind creates maneuverability challenges and can lead to dangerous situations for ships in ports and confined waters, while shipping safety in open seas is more affected by high waves generated by the 'jugo'. An example of the 'bura' wind's impact on maneuvering a cruise ship in the protected Bay of Kotor in the Adriatic can be found in [47]. In contrast, ferry accidents in the open Adriatic Sea, as discussed in Section 4.3, are generally attributed to waves, as reported by witnesses.  
It is important to clarify that only delay-related costs are considered in the present study (Sections 4.1 and 4.2), while other potential costs caused by heavy weather, such as damage to cargo, equipment, or ship structures, are omitted. This approach is justified for the Adriatic Sea, which is the mildest sea basin in the Mediterranean [24]. As a result, ship structural damage is rare due to the extremely low probability of severe environmental conditions in the Adriatic. Ship structures are generally designed to withstand more extreme conditions.  
However, the inclusion of other costs in the risk assessment is straightforward, as described in Section 2.5. Using risk as a performance indicator to account for structural consequences induced by different limit states to evaluate optimal ship routing is presented in [36].