The ‘interlocking’ system in Railways

Subject : Science and technology

Section: Msc

Concept :

Minister for Railways said that a change in the “configuration” of the track had led to the Coromandel Express smashing into the stationary goods train from behind, triggering the three-way train accident in Odisha in which 275 people have died so far.

Interlocking in railway

Interlocking in railway signalling systems is a crucial safety mechanism used in the operation of train movements on railway tracks.
It ensures that train movements continue without any conflicts with each other, preventing accidents.
There are three main components that comprise an interlocking system:
the point,
the track occupancy sensing devices, and
the signal.
The Interlocking system coordinates the functions of these three components to control train movements.

Function of each of these three main components

Signals (which are lights of green, red, and yellow colour) are installed along the tracks to indicate the status of the track ahead.
Track circuits are electrical circuits (also known as track-occupancy sensing devices) that detect the presence of trains.
Points allow trains to change tracks.

How safe is this system?

If any of the three components (signals, points, and track occupancy sensors) does not correspond to the overall ‘safe’ logic fed into the computer, the system will work to stop the oncoming train.
This means if the point is not locked, or not set to the desired direction, and/ or if the sensing device detects that the track is not clear, the signal will automatically turn red.
This is called a “fail safe” system — one that errs on the side of safety.

Who operates and monitors the interlocking signalling system?

The interlocking system is usually operated and monitored by trained personnel from the signalling and telecommunications department in Railways, often known as ‘signallers’ or signal operators.