Systems Of Railway:
The railways can be provided above and below the ground surface suiting to the topography of the area. Further, the railways below the ground surface can be constructed just below the ground level or at greater depths.
There are four systems of railways:
1. Surface railways
2. Elevated railways
3. Underground railways
4. Tube railways.
1. Surface Railway:
In this system, railways are provided over the ground. This is the most extensively used and best rails throughout the world. In surface railways, various means like level crossings, over bridge, under bridge etc are to be provided for crossing of the railway and road traffic safely and efficiently.
2. Elevated Railway:
In this system, the railways are provided at higher or elevated portion above the surface. A continuous viaduct supported on piers, columns etc are constructed and the track is carried on its steel deck. This system is very costly because stations, waiting rooms, offices are to be constructed at higher levels requiring staircases, escalators etc. This type of railways is proved in the heavily congested urban area where underground railways cannot be constructed.
3. Underground Railway:
In this system, the railway is provided just below the ground level. Tunnels are constructed for carrying tracks through them and an overbridge is necessary at every road-crossing to carry the road traffic over the railway traffic. Due to ventilation problem in tunnels, electricity is the only source of power for traction in underground railways.
This system is provided in the heavily congested area where the traffic intensity on roads is heavy.
a) This system provides rapid and unobstructed transportation.
b) This system helps in reducing traffic congestion problems.
c) This system provides safety during aerial attack in war.
4 Tube Railway:
The railway provided underground at a greater depth of about 18 m or more(upto 52 m) is called tube railway.
This system of railways is so called as the section of the underground tunnels, carrying the track, is circular like a tube. The main purpose of providing tube railways is to avoid the interference of the tracks with water and gas pipes, sewerage systems and oil or drainage pipes etc.
Some important features of tube railways are given below:
1. The railway stations have to be of cylindrical form.
2. Escalators or moving staircases are to be constructed to reach the tube railways.
3. Only electric traction is to be used to avoid the smoke and ventilation problems.
4. Automatic signaling system is to be used.
5. Such a mechanism of the train is to be used that it cannot start until all the doors are closed and it automatically stops, is the signal is at stop position.