## 3 Evaluation of Damage in Turnout System Using FMEA
### Calculation of RPN by Turnout Component  
Table 4 shows the damage ratios by turnout component according to the turnout system maintenance records data. The damage ratios for the different types of components were in the order from highest to lowest, as follows: rails, joints, bolts, wooden sleepers, baseplates, and the fastening system. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Components** & **Damage Quantity (EA)** & **Damage Ratio (\%)** & **Ranking** \\ \hline Rails & 410 & 67.84 & 1 \\ Joints & 107 & 17.76 & 2 \\ Bolts & 51 & 8.51 & 3 \\ Wooden sleepers & 21 & 3.41 & 4 \\ Baseplates & 10 & 1.61 & 5 \\ Fastening system & 5 & 0.87 & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Ratios of damage by component. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Item** & **Level of Influence on Related Components and Turnout System** & **Score** \\ \hline Very High & Train service cannot run unless problem is resolved & 5 \\ High & High impact on turnout system, including related components & 4 \\ Medium & Medium-level impact on turnout system, including related components & 3 \\ Low & Low impact on turnout system, including related components & 2 \\ Very Low & No impact on turnout system, including related components, even when this & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Impact score criteria. For occurrence, according to the results of historical record analysis on the turnout system, the range of values was calculated based on the frequency of damage occurrence on the component. As it was not possible to obtain all actual occurrences of damage, the results of on-site inspections of the urban railway wooden sleeper turnout were incorporated, and the range was classified based on the analyzed on-site inspection data values, as shown in Table 5. For approximately 0 occurrences, 1 point was assigned, followed by 2 points for 1-10%, 3 points for 10-20%, 4 points for 20-25%, and 5 points for 25% or more. With regard to the occurrence (P) scores for the rails, the crossing (47.1%) had the largest damage quantity, scoring 5 points, followed by the switch toes (19.8%) and normal rail (13.9%) with 3 points each, followed by the check rail (9.6%), closure rail (6.9%), and stock rail (2.7%) with 2 points each. Conversely, with regard to the P scores of the non-rail components, the calculation results were 4 points for the joint bolt and heel block bolt, 3 points for the crossing baseplate and switching bolt, and 2 points for all other components. The components that could be improved in terms of their P score were the crossing rail, switch toes, joint bolt, heel block bolt, crossing baseplate, and switching bolt. Among these, the P scores for the four non-rail components were: 4 points for joint bolts and heel block bolts (20 \(\leq\) occurrence \(<\) 25) and 3 points for crossing baseplate and switching bolt (10 \(\leq\) occurrence \(<\) 20). The P scores of these components could be improved by reducing the occurrence of damage. Therefore, an effective method must be applied to increase the occurrence score. For estimating the sensitivity (S), the quantity of damage occurrence was included in the calculation, and the value was obtained by applying the weights assigned according to the relative comparison of components, such as rails, by in-house maintenance experts. As the occurrence was reflected in the calculation, the range of the sensitivity calculation criteria needed to be increased. Therefore, the weight was applied to occurrence and the sensitivity score was calculated as presented in Table 6.  
The sensitivity score was based on a numerical rating that indicated the effect of the operation of the train in the event of failure. The sensitivity rating was the highest at 46.9% and 37.41% for the crossing rail and switch toes, respectively; a sensitivity score of 5 points was assigned for each of these components. Conversely, the sensitivity scores of the other types of rails were all assigned 2 points.