1. Land saving: Tunnels can reduce land occupation and construction cost.
2. Reduce terrain obstacles: Tunnels can avoid obstacles encountered when building railways on complex terrain and improve the operational efficiency of railways.
3. Enhance safety: The tunnel can provide a relatively closed space for passengers, reduce exposure risks and improve the safety of railway operation.
4. Improve the running speed: the track conditions in the tunnel are relatively stable, which can improve the running speed of the train.
5. Protect the ecological environment: the tunnel can avoid the railway construction in nature reserves and help protect the ecological environment.
Therefore, high-speed trains often pass through tunnels.