Necessity of Tunnels
The necessity of tunnels are as follows:
1. Tunnels are necessary, to avoid the long road and railway track construction along the surface of the hill to reach out the other side of the hill.
2. Tunnels are constructed for connecting the two terminal stations, which separated by a mountain.
3. To avoid more depth of open-cut to reach the other side of a mountain. It will be hard to build and maintain if the required depth of the open-cut exceeds 20 m.
4. To protect the road or railway from blockage at high altitudes due to landslides or snowfall.
5. To provide traffic safety from the climatic disaster at high altitude.
6. To save time, so they can use that time for another purpose.
7. To provide a fast and continuous transportation system in large towns, and to avoid holding traffic for a long time due to traffic congestion.
8. To avoid the use of valuable land and property for a road or railway project.