‘Electronic interlocking’, ‘point machines’, and their links to the Odisha train crash

At Bahanaga Bazar station in Odisha, the interlocking system was wrongly set which caused Shalimar-Chennai Coromandel Express to enter a loop line instead of continuing on the main line, and smashed into a stationery freight train

As the damaged tracks at the Bahanaga Bazar station in Odisha are being restored so that train operations can be resumed on the route, the focus has shifted to the cause of the horrific train accident involving three trains. According to the latest reports, 270 lives have been lost in the tragedy, and over 800 people are being treated in various hospitals.

Today Railway Minister Ashwini Vaishnaw said that the cause of the accident and the people responsible for the same has been identified. While he said that the matter is being investigated by the Commissioner of Railway Safety and it will not be proper for him to comment on it, he added that the accident took place due to a change in electronic interlocking.

It is notable that the Commissioner of Railway Safety is under the Civil Aviation Ministry.

Vaishnaw also said that the accident has nothing to do with the absence of the Kavach anti-collision system, adding that things like electronic interlocking, point machines etc were involved in the matter.

Before the comments of the railway minister, a preliminary probe report on the accident was leaked to the media. From the comments of the railway minister and the preliminary probe report, here is what can be derived on what had happened and how it could have taken place.

First, let's first understand what really happened on Friday evening at the small railway station named Bahanaga Bazar station in Balasore district in Odisha on the Kharagpur–Puri line. This line is part of the Howrah–Chennai main line under Kharagpur railway division of South Eastern Railway zone, headquartered at Garden Reach, Kolkata.

As it is a dual-track route, there are two main lines at the station. Apart from that, there are two loop lines on the outer side of both the main lines. Actually, there is another loop line next to the up main line, but it was unoccupied, therefore keeping it out of the discussion for simplicity. The loop lines are used to halt trains to allow faster or more important trains to pass them.

At the time of the accident, both the loop lines were occupied by two freight trains. At around 7 PM, Shalimar-Chennai Coromandel Express (12841) and Bengaluru-Howrah Superfast Express (12864) were to cross each other at the station on the main lines. Coromandel Express was travelling from Shalimar in Howrah to Chennai on the up main line, and the other train was in the opposite direction on the down main line, heading towards Howrah from Bengaluru. There was no stoppage of the two passenger trains at the stations and therefore they were running at high speed.

But when the Coromandel Express entered the station, it diverted to the up loop line instead of continuing on the up main line. As a result, it smashed into the parked goods train on the loop line. Such was the speed of the Coromandel Express that its locomotive climbed onto a wagon of the freight train. As a result, its coaches derailed.

At that moment, Bengaluru-Howrah Superfast Express had already arrived and almost crossed the station. But its last few coaches were hit by the derailed coaches of the Coromandel Express, resulting in the second passenger train also to derail.

The goods train that the Coromandel Express crashed into was loaded with iron ore, therefore, it was very heavy. As a result, it didn't move much due to the impact, and the entire force of the impact was absorbed by the coaches of the passenger train.

Therefore, it has been almost confirmed that the deadly accident took place because the Coromandel Express entered the loop line instead of going straight on the main line.

As the passenger train entered the wrong track and smashed into the goods train, this means the interlocking system, which selects whether the train will go to the main line or the loop line, was wrongly set. Both the preliminary report and the railway minister has confirmed this.

The interlocking system is a set of systems that ensures that the correct track is selected for an incoming or outgoing train, and the correct signal is displayed accordingly. This system consists of the points or switches, through which one track merges with another. The points enable the trains to move from one track to another.

The points are laterally moveable rails with tapered ends, which can be aligned with either of the two tracks and then locked in position. To change alignment, it is unlocked, moved, and locked to the new position. The signals are linked to this mechanism, which ensures that wrong signals can't be given.

Earlier, the points were moved manually using levers. It this system, the points are attached to cables and rods, and going through a system of pullies, they end at levers positioned at the signal room. The levers are moved manually to switch the points. Later, the manual switching systems were replaced with mechanical systems that use electrical power to move the points and change the signals.

Now, electronic interlocking systems are used, which perform the same task, but with electronic and electrical devices. In this system, points are moved by pressing switches on the control panel, and based on the signal from the panel, tracks are moved by electronic point machines installed at the points. These devices have motors and other equipment to move the points and are located next to the switching points, connected with them via rods. The point machines are connected to the control room by wires. Based on the position of the points, information is shown on the dashboard in the control room.

The positions of the points are displayed on a dashboard in the signal room either using coloured lights on a layout of the tracks or a digital display screen. When the point is set for the train to continue on the main line, it is called the normal position. And when it is set for the train to enter the loop line, it is called the reverse position. The current positions of all point machines are displayed on the screen on a real-time basis. The screen also displays the positions of trains on various tracks.

After all the points are set correctly for a train, the signals are automatically set to green by the interlocking system.

In smaller stations like Bahanaga Bazar, there are only a small number of lines and switching points, and a train can be given the green signal by setting just one point in the correct position. But in bigger stations, junctions and terminals with a large number of tracks, dozens of switches are required to be set to the correct position for a train to be given the green signal.

When the goods train carrying iron ore arrived on the up line at the station, it was diverted to the up loop line by setting point 17A to reverse position. After that, the point was to be switched back to the normal position, so that Coromandel Express can move ahead on the main line, as it does not have a stoppage at the station.

According to the preliminary report, a signal was given for the main line for the passenger train, but it was subsequently switched off. This means, while the point was switched to the normal position, it was changed back to the reverse position. This led the train to the loop line, causing the accident.

Here's how exactly it unfolded #Train #TrainAccident #CoromandelExpress pic.twitter.com/YBwedC2Hs6

The preliminary report states that point no 17A was set for the loop line in the reverse position. However, in the panel, it was showing that the main line and the point were in normal position. This means, there was some fault which caused the panel to not show that the point was actually at the reverse position, leading the passenger train to the loop line, and instead it showed the normal position.

Two officials of Railways, Principal Executive Director of Signalling Sandeep Mathur and Member of Operation and Business Development Jaya Varma Sinha, have also confirmed the cause of the accident. "Only one train was involved in the accident, it was the Coromandel Express. The Coromandel Express crashed with the goods train and its coaches went on top of the goods train," said Sinha.

She added that there was no question of overspeeding by both the passenger trains, and they were running at their approved speeds. She also said that there was no fault by the driver of Coromandel Express, as loco pilots depend on the interlocking system, believing it is set correctly by the station staff.

Railway Minister Ashwini Vaishnaw said that the person responsible for this has been identified, which indicates that the fault took place due to an error by someone responsible to operate the points. It is being speculated by some that point 17A was set to reverse after the iron ore train arrived so that it can be moved to the loop line and the passenger train can proceed straight. But after that goods train entered the loop line, the point was not set for the normal position due to some reason, causing the passenger train also to enter the loop line.

However, why the incident took place is a matter of a detailed investigation. It was most probably a mistake by Railway staff, but conspiracy theorists are claiming that it was deliberate. That is a very serious allegation, therefore it will be better to wait till more information emerges.

But it is by now confirmed that the accident took place after the Coromandel Express entered the wrong track due to a wrongly set interlocking system, causing it to smash into a goods train. It is also confirmed by now that it was not a head-on collision between two passenger trains. Such collisions mostly don't happen these days due to the presence of dual tracks. But the passenger train did move into a track that already had another train and hit it at high speed, resulting in a rear-end collision.

This also dismisses the claim that the Coromandel Express derailed on its own and then its coaches hit the goods train and the other passenger train. If that had happened, the Locomotive of the Coromandel Express would not have ended up on the top of a wagon carrying iron ore.

Whether NDTV or 'The Wire', they never have to worry about funds. In name of saving democracy, they get money from various sources. We need your support to fight them. Please contribute whatever you can afford

Enter your email address: