## 4 Redesigning Precautionary Area to Roundabouts  
### AIS Data Analysis  
Analysis of the AIS data resulted with a total of 486 ships identified; A total of 250 of these (51% of the traffic) were bulk carriers (196 ships were engaged in Australia-Far East Asia trades). There were 183 ships with lengths measured between 251 and 300 m. Among all the ships, 64% were foreign-flagged. In addition, 80% of these ships were built after 2000. Traffic in the strait is illustrated by ship movement in Figure 5.  
Figure 4: Monthly traffic in 2023. Figure 5: Movement of marine traffic in the Lombok Strait. (**a**) Passing ships; (**b**) crossing ships; and (**c**) coded route according to traffic direction. Figure 5a displays the organized passing traffic in the area, in contrast to Figure 5b, where the crossing ships are depicted. The movement of ships in the southern precautionary area adhered to the crossing ships accordingly (routes E1 and E2); although dense, they managed to utilize the precautionary area to cross, unlike that depicted in the northern precautionary area. The amount of traffic during the 7 d observation period according to the coded route in Figure 5c is shown in Table 2.  
A total of 608 ship movements during the 7-day observation period were noted, where the third day was the densest day, and route B was the densest route. A visualization of traffic in the strait is depicted in Figure 6.  
A high density of traffic approaching Padang Bai and Lembar Port was observed in the visualization of the heatmap in Figure 6a. The concentration of passing ships related to the traffic lane can also be clearly seen in Figure 6b, where the movement of ships in route A followed the outer limit of the TSS, whereas the ships in route B used the middle of the TSS. Ships crossing routes E1 and E2 used the southern precautionary area. The most interesting case was in the northern precautionary area, where ships crossed the C1, C2, D1, and D2 routes. The details of the number of ships adhering to the northern precautionary area of the TSS are listed in Table 3. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**Route**} & \multirow{2}{*}{**Description**} & \multicolumn{8}{c}{**Daily Ship Number**} \\ \cline{5-10}  & & & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **Total** \\ \hline
1. & A & TSS Southbound & 18 & 22 & 23 & 18 & 24 & 32 & 16 & 153 \\
2. & B & TSS Northbound & 30 & 20 & 29 & 24 & 17 & 16 & 23 & 159 \\
3. & C1 & Bali–North Lombok & 2 & 3 & 2 & 3 & 4 & 3 & 2 & 19 \\
4. & C2 & North Lombok–Bali & 2 & 2 & 5 & 2 & 2 & 3 & 2 & 17 \\
5. & D1 & Lombok–North Bali & 6 & 6 & 5 & 6 & 7 & 7 & 7 & 45 \\
6. & D2 & North Bali–Lombok & 7 & 6 & 9 & 6 & 7 & 5 & 8 & 48 \\
7. & E1 & Bali–Lombok & 12 & 13 & 13 & 12 & 13 & 11 & 10 & 85 \\
8. & E2 & Lombok–Bali & 9 & 13 & 12 & 12 & 12 & 13 & 82 \\  & Total & 86 & 85 & 98 & 83 & 86 & 89 & 81 & 608 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Number of traffic in the study area. Figure 6: Kernel density estimation (KDE) visualization of the marine traffic in the research area using GIS; (**a**) magma color ramp heatmap with 10 mm radius and (**b**) heatmap with each square representing an area of 450 m.  
Comparing Tables 2 and 3, the number of specific ships that adhered to the northern precautionary area (C1, C2, D1, and D2) was less than expected. Only eight ships used the C1 route out of seventeen ships (42%); one out of seventeen used ships the C2 route (5.8%); twenty out of forty-five ships used the D1 route (44%), and fourteen out of forty-five ships used the D2 route (29%). Overall, only 33% of all ships adhered to the given precautionary area. This was also discussed with VTS managers, supervisors, and operators, as they mentioned that despite warnings and penalties from VTS, ships tended to follow their natural path (straight to destination).