# Navigational Risk Assessment in Offshore Wind Farms Using Spatial Ship Domain Models
## 3 Results
### The Numeric Factors \(R_{\text{N}LF}\) and \(R_{\text{N}LA}\) Estimated for Three Ship Types  
In this paper, as in previous studies [8], it is assumed that the distances between offshore installations in the OWF area range from 700 m for substations and 1000-2000 m for wind turbines. However, this analysis expands to include seven different distances: 150 m, 300 m, 500 m, 600 m, 700 m, 800 m, and 1000 m. Table 12 (Appendix C) presents navigational risk indicators for different ship domain lengths ahead of and astern of representative ship types in the OWF area, considering average hydrometeorological conditions. Calculations were based on PIANC guidelines, [PERSON]'s 2D domain model, and [PERSON]'s 3D domain model, which account for turning circles and emergency stop maneuvers.  
For large vessels over 250 m (e.g., VLCC), navigational risk only significantly decreases when distances from hazards exceed 1000 m. The analysis shows that for a VLCC, risk indicators are acceptable only beyond this distance. The greatest distance between wind turbines in the OWF is 1976 m, meaning the minimum safe distance from hazards is approximately 988 m. Even then, VLCC navigation in the OWF area still entails some risk.  
For smaller vessels like fishing boats or Z-Tugs, the risk of allision remains high at distances under 150 m, even at reduced speeds and favorable conditions. For Z-Tugs, the risk drops below 0.0 at distances beyond 250 m. Although lower risk values are noted for smaller vessels, the safety zone around wind turbines, according to PIANC guidelines, is 500 m. However, the PIANC method does not clearly define which vessels are considered small or large. The analysis concludes that navigating a VLCC in the OWF area is extremely risky and should be avoided, while smaller vessels could enter the area in emergencies.  
The Numeric Factors of \(R_{\text{N}WP}\) and \(R_{\text{N}WS}\) Estimated for Three Ship Types  
Table 12 (Appendix C) highlights the navigational risk indicators R\({}_{\text{N}WP}\) (SD\({}_{\text{W}P}\)) and R\({}_{\text{N}WS}\) (SD\({}_{\text{W}S}\)), which relate to maintaining safe distances from hazards on a ship's port and starboard sides. The results reveal significant variation in risk levels depending on the method used. The PIANC method, the most restrained, shows higher risk values (indicated by red fields), but its results are minimally affected by vessel size and do not account for actual maneuvering capabilities. This makes it less practical for smaller vessels like fishing boats and Z-Tugs. For example, with a 350 m distance from the nearest hazard, the PIANC method gives a risk indicator of 0.61 for fishing boats and 0.55 for Z-Tugs on the port side, and 0.76 and 0.74, respectively, on the starboard side.  
In contrast, the [PERSON] 2D domain method and [PERSON]'s 3D domain model suggest safe navigation for both vessel types regarding side hazards. While [PERSON]'s model is comparable to [PERSON]'s for emergency turns at full speed with a 35\({}^{\circ}\) rudder angle, it only considers the horizontal plane (XY) and ignores obstacles above or below the water. [PERSON]'s 3D model accounts for these factors and helps in selecting appropriate anti-collision maneuvers by adjusting the ship's course or speed.  
For instance, when evaluating the R\({}_{\text{N}WP}\) (SD\({}_{\text{W}P}\)) and R\({}_{\text{N}WS}\) (SD\({}_{\text{W}S}\)) for a VLCC at 500 m from the nearest hazard, a full-speed starboard turn shows a 42% risk on the starboard side (R\({}_{\text{N}}\) = 0.42). An emergency stop reduces this risk to 18% (R\({}_{\text{N}}\) = 0.18), and a half-speed stop lowers it to 5% (R\({}_{\text{N}}\) = 0.05).