## 3 Results  
### Representative Risk Factors  
On the basis of the expert opinion and literature review, the following factor criteria were formed, including relevance, influence level, incidence rate, and representativeness. Subsequently, the members of the decision-making group discussed and analyzed the initial risk factors on the basis of the selection criteria and, finally, reached a consensus for the final measurements. In the risk factors analysis of a ship collision, the relevance was represented by \(RF1\), the influence level was represented by \(RF2\), the incidence rate was represented by \(RF3\), and the representativeness was \(RF4\). We selected mainly the risk factors with high representativeness, so the set and inference were as follows:  
\(U=\{1,2,3,\ldots,\ldots,n\},n=1\sim 29\)  
\(Q=\{RF1,RF2,RF3,RF4\}\)  
\(RF1=\{H,M,L\}\)  
\(RF2=\{H,M,L\}\)  
\(RF3=\{H,M,L\}\)  
\(RF4=\{H,M,L\}\)Then, we created a decision table based on Table 4 data and imported it into ROSE2. After calculation and analysis of rules induction and optimization by ROSE2, there were five decision rules, comprising three decision rules (i.e., RF4 = L, RF4 = M, and RF4 = H) and two approximate rules (i.e., RF4 = M and RF4 = H). The calculated results are shown in Table 5.  
We selected the highly representative risk factors, Decision Rule 3: RF1 = H and RF2 = H and RF3 = H, then RF4 = H, to obtain a comprehensive and effective risk assessment. The risk factors with high relevance, high influence level, and high incidence rate included carelessness, personal improper operation, unfamiliarity with local navigation regulations, unfamiliarity of ship characteristics, mechanical malfunction, poor weather condition, and traffic density. * Carelessness  
Carelessness is the main cause of ship collisions and other maritime accidents because of the weak safety awareness. Carelessness among a crew can take various forms, including failing to detect obstacles ahead and neglecting to adjust course or speed in a timely manner while operating the vessel. In addition, weak safety awareness can be a contributing factor, such as relying solely on past successful experiences and disregarding essential collision avoidance procedures [6; 22; 68]. * Personal improper operation  
When a ship is sailing, it can use radio broadcasts or whistles to warn other ships. Additionally, the ship's engine or rudder can be used to adopt avoidance procedures to prevent collision events. However, sometimes ship collisions may occur due to improper operations by the crew sailing on duty, such as the wrong engine orders and rudder orders. In addition, ship collision may also occur when the helm chief operates incorrectly, such as operating starboard into port [6; 68; 69]. * Unfamiliarity of local navigation regulations  
There are seven international commercial ports in Taiwan, and each commercial port has its own navigation regulations for the main channel and the meaning of the signal board. In addition, the anchoring area and the traffic separation scheme (TSS) have different regulations due to the local sea conditions. Furthermore, it is difficult to ensure that the crew on the ships have sufficient knowledge of local navigation regulations since various types of ships pass through the ports, including work ships, ferries, sightseeing transportation ships, and fishing ships. In particular, fishing boats have neglected the TSS regulations for fishing operations. Therefore, collisions between two ships occur frequently, as well as collisions between ships and other facilities [6; 68; 69]. * Unfamiliarity of ship characteristics  
There are many types of ships, such as container ships, general cargo ships, bulk carriers, oil tankers, work ships, ferries, sightseeing boats, and fishing boats, and the characteristics of the vessels are different due to their purposes. Moreover, even the same type