# Assessment of the Vulnerability of Selected Key Elements of Rail Transport. Slovak Case Study
## 4 Discussion  
The reference route for verification of the functionality of the proposed model is the Kosice-Zilina line, which meets the criteria of irreplaceability and uniqueness. There are two railway bridges and three railway tunnels in this section, which have a significant influence on each other. If we consider the Zilina railway station as the starting point, there are railway bridges on the line, which are directly connected to Streeno II and Streeno III railway tunnels. It is the direct interconnection of these objects that, if destroyed, could cause serious problems during renewal. The direct connection between the tunnel and the bridge makes it difficult to access the tunnels, especially access to the tunnels from the Zilina railway station. The access is possible only from bridge structures, which in the case of their damage or destruction would require, first, the renewal of the bridge structure, then the renewal of the destroyed tunnels. It follows that the renewal would be time-consuming with high economic losses due to the importance of the route. The financial complexity of the renovation is further exacerbated by the fact that there is a significant Zilina-Teplicka marshaling yard nearby. With regard to the illustrative processing of the calculation of the tunnel vulnerability in this paper, we also present the verification of the functionality of the proposed model for the example of the Streeno I tunnel. The Streeno I tunnel is a double-track electrified tunnel with a length of 318 m which was built between 1937 and 1939 due to the straightening of the route in the Streeno-Dubna skala pod Kosariskami section. At the end of the Second World War, it was severely damaged; after a previous temporary repair, it was fully repaired and put into operation in 1946. The tunnel tube has 46 tunnel belts and 6 safety alcoves on both sides. In 2001, it underwent a major reconstruction. To drain it, it was enough to clean the existing drainage channel. All parameters and their values are shown in Table 15. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Criterion** & **Parameter** & **Value** & \\ \hline \multirow{4}{*}{K1—detour route} & P1—the length of the detour route & no detour route & 100\% \\ \cline{2-4}  & P2—number of detours routes & no detour route & 100\% \\ \cline{2-4}  & P3—level of adequacy of the substitution & impossibility to replace the original route & 100\% \\ \hline \multicolumn{4}{c}{Calculation: (100 + 100 + 100)/3 = 100} \\ \hline \multirow{4}{*}{K2—construction characteristics} & P1—tunnel length & 318 m & 20\% \\ \cline{2-4}  & P2—age of tunnel & 80 years & 60\% \\ \cline{2-4}  & P3—ground speed & 100 km/h & 60\% \\ \cline{2-4}  & P4—number of tracks & Two & 50\% \\ \hline \multicolumn{4}{c}{Calculation: (20 + 60 + 60 + 50)/4 = 47.50} \\ \hline \multirow{4}{*}{K3—significance of the element} & P1—part of the pan-european corridors & Yes & 100\% \\ \cline{2-4}  & P2—part of the RFC corridors & Yes & 100\% \\ \cline{2-4}  & P3—significance from the economic point & track of the 1. category & 100\% \\ \hline \multicolumn{4}{c}{Calculation: (100 + 100 + 100)/3 = 100} \\ \hline K4—traffic performance & P1—useful track load & 2. category & 75\% \\ \hline \multicolumn{4}{c}{Calculation: 75} \\ \hline \multirow{4}{*}{K5—risk assessment of the area} & P1—type of rock terrain & granite & 33\% \\ \cline{2-4}  & P2—water leakage & slightly damp & 50\% \\ \cline{2-4}  & P3—access to tunnel and & without fire-fighting equipment, with & 75\% \\ \cline{2-4}  & fire-fighting equipment & access to one portal & \\ \cline{2-4}  & P4—rail failure & 10.34\% & \\ \cline{2-4}  & P5—signaling error & 5.60\% & \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Parameters and their Values of Streeno I Tunnel. The significance criteria and the calculation of vulnerability for the Strecno I tunnel is in Table 16.  
On the basis of the above assessment, the vulnerability of the Strecno I tunnel is high (Table 17).