Odisha Train Tragedy: Understanding Interlocking System Which Is At The Centre Of CBI Probe

Odisha Train Tragedy: Railway Minister Ashwini Vaishnaw cited the change in the interlocking system as a likely cause for the crash of the Coromandel Express which resulted in the deaths of over 270 people. However, the malfunctioning of an electronic interlocking system is considered to be a rare occurrence. The failure of an interlocking system can be attributed to two reasons: the signal maintainer deviating from established protocols or the signal was manipulated by someone who has enough understanding to do so. The suspicion that someone could interfere with the source code in this AI-based interlocking system led the government into ordering a CBI probe.

An interlocking system is the backbone of any railway network as it decides the track on which a train runs. This system provides the framework which ensures the safe and efficient movement of trains at junctions, stations and signalling points. The interlocking system has three key components: Switch Points, Track Circuits and Signals.

Switch points are essentially the moveable section of the track which lead a train from one track to another. The switch point needs to be activated well in advance so that the incoming train can pass over the switch to another track smoothly. These switch points manipulate all the movement of trains from one track to another and are quite essential for the smooth and safe running of trains.

The track circuits are installed to detect a train's presence on a given track. Only when the track circuit determines that a track is vacant and no other train is stationed on the other track, the switch points are activated which help the train to navigate the tracks.

The signals for a particular train movement can only be given once all the points and crossings for the movement have been correctly set, locked and verified that the route is free of any obstruction (mostly a train).

Though the probe findings are yet to be made public yet the Railway Minister claimed that the "root cause" of the Odisha train tragedy was the malfunctioning of the interlocking system. The preliminary finding has found that there was a signalling issue as the Coromandel Express was given a green signal after which it switched to the loop line where it crashed with the goods train and its coaches went on top of the goods train. The Coromandel Express switching to the loop line could be because of wrong signalling or faulty routing which means the switch points got wrongly aligned resulting in the train going to the loop line. Or the track circuit could not detect that another train was stationed on the loop line and the Coromandel Express was wrongly routed to the loop line.

The picture will be clear only when the final report is out. However, the interlocking system is considered to be "fail safe" which means even in a case of failure there will be a red signal on the tracks alerting the loco pilots to stop.