# Improving the Maritime Traffic Evaluation with the Course and Speed Model
## 4 Evaluation of Maritime Traffic Flow with the CS Model
### Evaluation with CS Models  
The selected assessment area was the entry route of Ulsan Port. Ulsan Port is an international port with a wide variety of vessels; basically, it has a high traffic volume, so various vessel patterns can be observed, and it has the characteristics of showing a balanced traffic volume at any time of the day, so it is an appropriate data sample to apply to the CS model. The AIS data from 1 to 30 September 2019 were used. Figure 2 illustrates the data for the target sea area. The data were preprocessed to remove outliers and interpolate the missing values. Standard plans for speed, acceleration, COG, and ROT were calculated from the preprocessed data. The data categorized by size can be accessed using each standard plan. Find Dk(x), Dk(a), Dk(\(\theta\)), and Dk(r). Based on this, Ispa and Icon were obtained. Ics represents  
Figure 2: Target sea area. the average of Ispa and Icon. Figure 3 schematically illustrates the data processing and CS model calculation procedures. The continuity index was computed by analyzing the speed and acceleration distribution of ships traversing the assessment area, categorized by size. Using the AIS data of the target sea area, the speed was plotted against distance, and for the acceleration, the value was obtained by differentiating the speed in the same way. The results are shown in Figures 4-7. The categories were as follows: S1 (length overall, LOA, under 50 m), S2 (LOA: 50-100 m), S3 (LOA: 100-150 m), S4 (LOA: 150-200 m), and S5 (LOA: 200-250 m). The standard plan of the speed and acceleration distribution for S1 exhibited more significant fluctuations compared to the distributions for S2 to S5. This was attributed to the tendency of smaller ships (under a 50 m LOA), which could be attributed to the characteristic of small ships below an LOA of 50 m rapidly reacting to the reduction in and acceleration of speed, as well as various types of ships passing by. Figure 8 illustrates the analyses of Dk(v) and Dk(a), respectively, for continuity. Dk(v) mainly ranges from about \(-\)5 to +5 knots during port entry, compared to the standard plan. D(a)k typically falls between \(-\)2 to +2 knots. However, a greater deviation from the standard plan was observed during port entry rather than departure. The values of D(v)k and D(a)k depended on the ship's navigation speed and acceleration; thus, they could vary based on the designated location and time of the target assessment area. Such values may diverge in areas with nonlinear segments, intersections of navigation flows with varying directions, and within harbors. Temporal variations may arise during peak navigation periods, as well as discrepancies between the day and night. The spatiality index was computed by analyzing the COG and ROT distribution according to ship size for vessels passing through the target assessment area. The outcomes are presented in Figures 9-12, with categories S1 (under a 50 m LOA), S2 (50-100 m LOA), S3 (100-150 m LOA), S4 (150-200 m LOA), and S5 (200-250 m LOA). Similar to the speed and acceleration distributions for continuity, the standard plan of COG and ROT distributions for S1 exhibited more significant fluctuations compared to the distributions for S2 to S5. Figure 3: Data processing and CS model calculation procedures. Figure 4: Speed distribution by ship size. Figure 5: Speed standard plan comparison by ship size. Figure 6: Acceleration distribution by ship size. Figure 7: Acceleration standard plan comparison by ship size. Figure 8: (a) Dk(v) analysis results; (b) Dk(a) analysis results. Figure 9: COG distribution by ship size. Figure 11: ROT distribution by ship size. Figure 12: ROT standard plan comparison by ship size. Figure 3:0 COG standard plan comparison by ship size. This was attributed to the tendency of smaller ships (under a 50 m LOA) to alter their course rapidly, resulting in a higher rate of convergence and a corresponding increase in the ROT value.