# Accident Risk Analysis of Gas Tankers in Maritime Transport Using an Integrated Fuzzy Approach
## 4 Findings
### Interaction Analysis Between Risks Identified by the FTA  
In the third phase of the study, the accident and environmental risks identified by the experts through the Fuzzy Delphi method were analysed using the Fault Tree Analysis \begin{table}
\begin{tabular}{l l l l l} \hline
**Risk Factor (R)** & **Cause Score (R)** & **Outcome Score (C)** & **R + C** & **R \(-\) C** \\ \hline R13 & 0.73 & 0.69 & 1.42 & 0.04 \\ \hline R14 & 0.86 & 0.90 & 1.73 & \(-\)0.04 \\ \hline R15 & 0.88 & 0.79 & 1.67 & 0.09 \\ \hline R16 & 0.85 & 0.78 & 1.63 & 0.07 \\ \hline R17 & 0.67 & 0.64 & 1.31 & 0.03 \\ \hline R18 & 0.65 & 0.70 & 1.35 & \(-\)0.05 \\ \hline R19 & 0.71 & 0.75 & 1.46 & \(-\)0.04 \\ \hline R20 & 0.72 & 0.78 & 1.50 & \(-\)0.06 \\ \hline \end{tabular}
\end{table} 
Table 6: _Cont._  
Figure 5: Cause-effect graphic. (FTA) method. Dynamic models combining FTA with Markov chains provide a tool for analysing component priorities, event sequences, and dependencies that may affect system reliability [65]. These methods help to bridge the gap between theoretical reliability analysis and its practical application in real-time, safety-critical environments [61]. Expert opinion has led to the development of an FTA diagram that is suitable for use worldwide. In the FTA diagram, gas fire and gas leak accidents were identified as the main factors. In the Fuzzy DEMATEL method, the risks obtained using Equations (A17) and (A18) and calculated using Equations (A19) and (A20) are divided into cause-and-effect groups. Causal risks are linked with an 'OR' gate, while effect risks are linked with an 'AND' gate. The FTA diagram is shown in Figure 6 below. The risks identified include risks that may arise during the operation of gas tankers. These risks may occur both during navigation cargo handling. The risks have been classified according to expert opinion and the values in the fuzzy DEMATEL below. To improve the clarity and traceability of the fault tree structure, Table 7 below summarises each risk factor, its target event in the fault tree, and the logical gate used to model its relationship. This table representation helps to consolidate the logic of the FTA diagram and makes it easier to understand which risks are directly causal and which operate through compound mechanisms  
Among the risks associated with a gas fire accident, the lowest priority, R10 (Damage to marine organisms on the tanker structure), which is of the lowest priority, is caused by the accumulation of small marine organisms on the hull, and structural damage is generally difficult to detect during routine inspections. R12 (Air pollution from gas operations)  
Figure 6: Main Fault Tree Analysis diagram. reflects the risk of hazardous atmospheric conditions during the handling of gas and is a health and safety concern for both the ship's personnel and port workers. R13 (Extreme weather conditions) poses significant risks to shipping and port operations due to the increasing frequency and intensity of adverse meteorological events. These risks--R10, R12, and R13--are linked by an 'OR' gate as they are the causes of risk R1 (Gas leakage during cargo handling) and represent potential risks contributing to the triggering of R1. The risks associated with a gas leak accident, listed from the bottom up, include R6 (Increase in tank pressure under the influence of seawater temperature), which refers to pressure fluctuations in pressurised tanks caused by rising seawater temperatures, R10 (Damage to tanker structure by marine organisms), which refers to the detection and assessment of harmful effects that are generally difficult to detect due to small marine organisms causing invisible damage to the hull, and R13 (Extreme weather conditions), which refers to the increasing frequency and intensity of meteorological events that pose a critical threat to navigation and port operations. These risks--R6, R10, and R13--are linked through the 'OR' gate and represent potential risks that could contribute to the triggering of risk R11 (Large gas leakage due to accident).