# Development of a Fire Risk Assessment Program for Submerged Tunnels
## 4 Validation of Submerged Tunnel Quantitative Risk Assessment Program
### Verification of Railway Tunnel Quantitative Risk Assessment Results  
The criteria for the evaluation and verification of general railway tunnels and rescue stations are presented in Table 5. The total risk of a general railway tunnel was found to be 3.12% lower in SFT_QRA compared to Rail QRA (Table 6). This reduction is attributed to the same reason observed in the QRA of road tunnels--despite analyzing the same fire scenario file, FDS inherently refines the time-step, introducing a discrepancy of up to \(1/100\)th of a second. This time-step difference affects the calculation of the Fractional Effective Dose (FED) used in determining the maximum number of fatalities.  
The total risk in the case of a rescue station installation was found to be 5.0% lower in SFT_QRA compared to Rail QRA. This reduction is attributed to the same reason observed in the QRA of road tunnels--despite analyzing the same fire scenario file, FDS inherently refines the time-step, introducing a discrepancy of up to \(1/100\)th of a second. This time-step difference affects the calculation of the Fractional Effective Dose (FED) used in determining the maximum number of fatalities.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Category** & **SFT\_QRA** & **Road\_QRA** & **Remarks** \\ \hline \multirow{4}{*}{Total risk} & General & \(2.1211\times 10^{-4}\) & \(2.1895\times 10^{-4}\) & \(\begin{array}{c}3.12\%\\ (Reduction) \\ 5.0\% \\ (Reduction) \\ \end{array}\) & \(\begin{array}{c}3.12\%\\ (Reduction) \\ 5.0\% \\ (Reduction) \\ \end{array}\) \\ \hline Estimated & General & \(2.12\) (persons) & \(2.18\) (persons) & \(\begin{array}{c}2.75\%\\ (Reduction) \\ 4.67\% \\ (Reduction) \\ \end{array}\) \\
10,000 years & Rescue station & \(1.02\) (persons) & \(1.07\) (persons) & \(\begin{array}{c}2.75\%\\ (Reduction) \\ 4.67\% \\ (Reduction) \\ \end{array}\) \\ \hline \multirow{4}{*}{One fatality} & Frequency & General & \(1.1992\times 10^{-6}\) & \(1.2792\times 10^{-6}\) & \(\begin{array}{c}6.25\%\\ (Reduction) \\ 5.0\% \\ (Reduction) \\ \end{array}\) \\ \cline{1-1}  & & Rescue station & \(1.0738\times 10^{-6}\) & \(1.1303\times 10^{-6}\) & \(\begin{array}{c}5.0\%\\ (Reduction) \\ 6.67\% \\ (Reduction) \\ \end{array}\) \\ \cline{1-1}  & Return period & General & \(833\),855 (years) & \(781\),739 (years) & \(\begin{array}{c}6.67\%\\ (Reduction) \\ \end{array}\) \\ \cline{1-1}  & & Rescue station & \(931\),258 (years) & \(884\),696 (years) & \(\begin{array}{c}5.0\%\\ (Reduction) \\ \end{array}\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Results of railway tunnel quantitative risk assessment.  
the analysis results. Therefore, the results can be regarded as equivalent, and it is reasonable to interpret them as producing the same outcome.  
A quantitative risk assessment was conducted to compare SFT_QRA, which was developed to include general railway tunnels and rescue station implementation, with the existing commercial QRA program, Rail QRA, under the same conditions. The results indicate that even when accounting for errors due to time-step refinement in fire analysis, the maximum error rate remained within 5.0%, ensuring the accuracy of the analysis.