HOW SIGNALLING SYSTEM IN INDIAN RAILWAY WORKS

How Signalling System in the Indian Railway Works

At first the most important thing to say that "A Driver of a train shall not start his train until he is authorised to do so". To give authority to the driver to start, signal posts have been erected at various places to indicate him whether to start or not. The driver shall not pass a signal unless he sees it has been TAKEN OFF i.e. Signal turned to either GREEN, or TWO YELLOW or ONE YELLOW. If the Signal is at ON position, i.e. RED, he must not pass it unless he is authorised to pass on a Written Authority issued by the Station Master. (This is done in case of Signal Failures).

There are certain circumstances in which although signal is RED, yet written authority is not required. For example GATE SIGNAL, INTERMEDIATE BLOCK STOP SIGNAL, AUTOMATIC SIGNAL.

To ensure a train shall proceed safely from one station to other there are various SYSTEMS of WORKING adopted in Indian Railways. The system adopted depends upon the density of traffic, i.e. more the number of trains the more costly the system adopted. Among this system, any one is followed for running of trains between two station. These systems are:

1.      ABSOLUTE BLOCK SYSTEM

2.      AUTOMATIC BLOCK STSTEM

3.      FOLLOWING TRAIN STSTEM

4.      PILOT GUARD SYSTEM

5.      TRAIN STAFF TICKETING SYSTEM 

6.      ONE TRAIN ONLY SYSTEM

ABSOLUTE BLOCK SYSTEM

Block Sections (in RED)

In Absolute System of Working a long section is divided into small blocks called BLOCK SECTIONS and the stations dividing the block sections are called BLOCK STATIONS. For a train to leave from a block station and proceed towards next block station, LINE CLEAR  must be obtained from the next block station. If the next station is able to receive the train then he gives the line clear to the rear station. This line clear is done with some device to enhance the safety. Generally ELECTRICAL BLOCK INSTRUMENTs are installed for such purpose. The system through block instrument is such that the signal from rear station cannot be given, unless line clear has been obtained from advance station through block instrument. This system is called Absolute Block system, because in this system, at any point of time, only one train can be in a block section running from a block station to another. It ensures perfect safety against two trains in one section.

AUTOMATIC BLOCK SYSTEM

This system is improvement over the Absolute Block System. In this a block section between two block station is further sub-divided into different block signalling section. Which means where one train can run between two block station in Absolute Block System, there more number of train can run in between two block stations.

ASPECTS OF AUTOMATIC SIGNALS

Sequence of Change of Signals with respect to running train in Automatic Block System

In Automatic Block System, each signals convey the aspect of next Signal(s) to the driver. For example, if a signal is ONE-YELLOW, it tells the driver that the next signal is RED. If it is DOUBLE-YELLOW, then next signal is DOUBLE-YELLOW or ONE-YELLOW, and if it is GREEN, then next signal is either GREEN or DOUBLE-YELLOW.

Each signals telling  the driver the aspects of next (few) signals helps the driver to run the train at more speed and helps him to control the speed when required.

Also Read: systemsof working in indian railways