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Problem with interlocking ’caused Odisha tragedy’. What is this key part of signalling system

Officials say nature of interference can only be revealed by report of Commissioner of Railway Safety. Minister Ashwini Vaishnaw says cause and culprits both identified.

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New Delhi: Even as the central government awaits the commissioner of railway safety’s (CRS) report on the Odisha train tragedy, senior Railways officials said Sunday that “interference” with the signalling system had been identified as the root cause of the accident, along with the people responsible. They added that the possibility of ‘sabotage’ had not been ruled out.

Speaking to reporters in Balasore Sunday evening, Union Minister of Railways Ashwini Vaishnaw said that given the situation and the administrative information received till now, the Railway Board has recommended that further investigation into the accident be carried out by the Central Bureau of Investigation (CBI).

Earlier in the morning, speaking to news agency ANI, the minister said the cause of the incident and the people responsible for it had been identified and the accident occurred due to a “change in electronic interlocking”. Interlocking is a key part of the signalling system.

As many as 275 people have died in a major train accident of Friday evening near the Bahanaga Bazar station in Odisha’s Balasore district, which involved three trains — the Shalimar-Chennai Coromandel Express (12841), the Sir M. Visvesvaraya-Howrah Superfast Express (12864), and a freight train. The incident left over 900 people injured.

Meanwhile, senior Railways officials said at a press conference in New Delhi Sunday that at this point, all angles were being looked at and that sabotage hadn’t been ruled out. They also said that Kavach, the indigenously developed anti-collision system, could not have helped, even if it had been deployed on the route. 

At the same conference, Railway Board Member Jaya Varma Sinha said that the systems are generally supposed to be tamper-proof or error-proof. For example, in case of any failure, the signal turns red to stop train movement. “…however, there was some kind of error (during Friday’s accident) …whether it was physical…for example, someone dug something without seeing whether the cable was cut etc… Or there is a short circuit… it usually doesn’t happen. But this is a machine… Any machine is 99.9% failure proof.” 


Also read: ‘Bodies all around, can’t believe I’m alive’ — Odisha tragedy survivors recall night of horror


Decoding electronic interlocking system

In the railway network, the signalling system is akin to a traffic light system seen on roads for the smooth running of traffic. It helps railways to safely operate approximately 10,000 passenger trains daily, on average. Interlocking is an integral part of the signalling system, which helps ensure that a train is not given a signal to proceed on a route that may already have another train running on it, leading to a collision or derailment.

An interlocking system can be electronic or manual, and in the case of the Odisha train accident, it was an electronic interlocking system – a fully software-driven approach to setting routes. A railway expert who did not want to be named told ThePrint that an interlocking system ensures that, before a train is given a go-ahead to move along a section of track, there are no other trains already on the track and there are no conflicting train movements that are already authorised.

Speaking at the press conference Sunday, Sandeep Mathur, the Railways’ principal executive director of signalling, explained that when the train needs to go via the main line, the driver gets a green signal, while for the loop line, the signal is yellow. 

In this case, the Coromandel Express driver was given a green signal, meaning it was safe for the train to go through the main line. “In this case, the interlocking system was electronic, meaning it was a computer-based system,” he said.

A preliminary inspection report by five Railways supervisors Saturday concluded that the green signal was given for the Coromandel Express to pass through the main line and then taken off — but the train entered the loop line, crashed into a stationary goods train and derailed. In the meantime, the second superfast express train coming from Bengaluru passed on the down line and its two coaches derailed after hitting the wreckage from the earlier crash.

Amidst lack of clarity on the exact sequence of events that led to the first collision, questions are also being raised about why the green signal given to the Coromandel Express was suddenly taken off. This has also given rise to speculation that the signalling system had manufactured or was tampered with.

‘Not ruling out sabotage’

Railway Board member Sinha said, “We are trying to determine whether the Coromandel Express derailed and hit the goods trains, or whether it collided with the latter and then derailed.” She said  the nature of the interference in signalling —  whether manual, incidental or weather-related — can only be revealed by the CRS through its ongoing investigation.

However, she also asserted that the Railway Board is aware of the preliminary “what possibly went wrong” but they cannot reveal it since the CRS investigation is currently ongoing.

Sinha said she had spoken to the locomotive pilot of the Coromandel Express shortly after the accident. “He said that the train had moved forward only after receiving the green signal for the main line. That is all he said at that time. Currently, his condition is critical and he is in hospital.”

She added that sabotage had not been ruled out, that the Home Ministry is assisting the investigation, and “not the National Investigation Agency”. “No aspect has been ruled out, as of now,” said Sinha.

Sudhanshu Mani, former general manager of the Integral Coach Factory under whose tenure the Vande Bharat train was conceptualised and executed, explained to ThePrint that the train driver has no control of steering while going from one track to another; it is the track itself that takes the train forward.

“.. which track to take and go forwards is called the route. The authority to proceed on that route is called the signal. Now, both signal and route have to be interlocked, otherwise if the route is something else and the signal shows something else, there is a chance of collision or going on the wrong route,” said Mani, a mechanical engineer himself.

“They have to be interlocked so that the route is not set in opposition to what signals say or the other way around. This is called interlocking, which is achieved either through a mechanical or an electronic or even advanced systems,” Mani said.

The interlocking is designed in a manner that if something fails, it goes into a safe mode but will not set a wrong route or wrong signal.

Kavach couldn’t have helped

Sinha, meanwhile, asserted that even if the Kavach system was in place, it would not have prevented the train from coming into contact “with the obstruction”. “For instance, if an obstruction occurs suddenly before a moving train — at a very high speed — Kavach will not help avoid the obstruction,” she said.

Another railway expert that ThePrint spoke to said the discussion on Kavach was digressing from the main issue. The Kavach system also takes inputs from the signalling system and hence, in this case, would not have been able to help. “Kavach works to avoid collision between two trains on the same track,” the expert said.

In light of the incident, the expert added that the Railways should focus on running trains safely and the maintenance of tracks and systems, rather than on issues such as adding more trains, focussing on high speed trains and station redevelopment. “This diverts the attention of officers from the core issues.

(Edited by Smriti Sinha)


Also read: Odisha train accident: Official flagged ‘serious flaws in signalling system’ in February


 

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