## 3 Results  
The Mokpo Harbor is a trading port located in the southwest of the Republic of Korea and is the fourth harbor in South Korea. There are 35 berths, 14 anchorages, and a shipyard that can build Panamax-sized ships adjacent to the docking facilities in the harbor. The Mokpo Harbor has a sea route of approximately 30 nautical miles from the entrance of Gasa-do (the starting point of the Mokpo VTS area) to the north wharf, where the Mokpo Harbor VTS is located. There are islands, reefs, shallow water zones, and bridges in the entire route section, requiring caution for navigation because there are frequent bends requiring diagonal turns [36]. Further, regarding the waterways that lead from the western part of Mokpo, the flood and ebb currents flow northward and southward, respectively. The currents turn approximately 30 min after the high and low tide, and the current speed reaches 4.0-5.0 knots [36]. Therefore, the Mokpo harbor and VTS areas were selected as target sea areas because it is appropriate to perform there the simulation for extracting traffic priority. The AIS data collected at the Mokpo Harbor VTS Center were used for the simulation, including all vessel navigation data for 30 days from 1 June to 30 June 2021. A total of 227,297,489 ship coordinates were collected during this period, and the extracted variables included the MMSI, date (including time), latitude, longitude, speed of ground (SOG), course of ground (COG), and heading data. In addition, the extraction ranges were 34\({}^{\circ}\)25\({}^{\prime}\)30\({}^{\prime\prime}\) N to 34\({}^{\circ}\)49\({}^{\prime}\)30\({}^{\prime\prime}\) N and 126\({}^{\circ}\)00\({}^{\prime}\)00\({}^{\prime\prime}\) E to 126\({}^{\circ}\)25\({}^{\prime}\)30\({}^{\prime\prime}\) E. The total data collection area is shown in Figure 6(a), and the number of coordinates was reduced to 72,308,388 as a result of extracting data from the target areas of Figure 6(b),c. After removing data on anchoring, mooring, or drifting vessels, 22,034,544 coordinates (930 vessels) were extracted. Further, Figure 8 shows a heat map prepared based on the density of 0 to 100 scales per pixel for the data following location-data refinement and location interpolation. Figure 7(a) shows the heat map created by classifying the received AIS data according to the target area, and Figure 7(b) shows the result created by extracting only the vessels navigating the target area, excluding vessels that are anchored, moored, or drifted. Figure 7(c) shows the results of position interpolation according to the standard time intervals. The data shown in Figure 7(c) were stored as data for clustering in the subsequent steps. \begin{table}
\begin{tabular}{c c c c c} \hline
**CPA** & **Danger** & **Threat** & **Caution** & **Attention** \\ \hline Danger & 1.0 & 0.9 & 0.7 & 0.4 \\ \hline Threat & 0.9 & 0.8 & 0.6 & 0.3 \\ \hline Caution & 0.7 & 0.5 & 0.3 & 0.2 \\ \hline Attention & 0.5 & 0.3 & 0.2 & 0.1 \\ \hline \end{tabular}
\end{table} 
Table 3: Initial fuzzy inference table of Pindex. Next, the result of the position interpolation in Figure 8c was grouped by the same time zone. This is essential for extracting the priority for all vessels existing at the same time via the rearrangement of the various AIS data receiving times to standard times. In this process, datasets that underwent data pre-processing were sorted according to the time zone (a total of 2881) to build a database for simulation. In previous studies on CRI calculation conducted from the perspective of a ship shown in Figure 9a, the risk relationship was defined based on the data received at the current time considering the expecting traffic situations between the own ship and targets [10,11]; however, in this study, all traffic situations of existing ships in the target area were considered, as shown in Figure 9b. Therefore, the data for all ships that exist within the same reference time must be extracted. Figure 8: Data pre-processing results by (**a**) target area, (**b**) target speed, and (**c**) position interpolation.