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Indian Railways will turn 200 years old in another thirty years and it has progressed from Steam Locomotives and Semaphore signals to WAP7 Locomotives and Electronic Interlocking System. The initial investigation in the Bahanaga accident in Odisha’s Balasore district is said to reveal a faulty signal that led Coromandel Express into the loopline where the goods train was halted. The brutal accident that involved three trains, the other being Yesvantpur – Howrah Express, brought the Train Collision Avoidance System or Kavach developed by the Research Designs and Standards Organization (RDSO) to the fore.

So what is Kavach and what does it do to avert such major train accidents? A key point is that Kavach automatically determines how far ahead the locomotive can travel safely without any obstruction. In case of any emergency, an SOS message is generated and brakes are applied automatically. “Coromandel Express: Did Modi govt give safety a backseat?” pointed out that the Parliamentary Standing Committee on Ralways in the Lok Sabha was told that as of March 2022, only a trial section of 250 km and another 1,200 route km in South Central Railway had been brought under it.

TCAS or Kavach is an indigenously developed Automatic Train Protection system which is meant to protect trains from Signal Passing at Danger (SPAD), excessive speed and collisions. The railway term SPAD means that the train has passed the red signal, which is a serious error. A SPAD usually results in the termination of the loco crew for negligence.

SPAD does occur for various reasons. Under TCAS, the trains are monitored for their movement continuously and are brought to halt by applying automatic brakes if the crew fails to do so or not in a position to do so whenever an unsafe situation arises like SPAD, overspeeding or collision with other trains. In addition to the display of speed, location, distance to signal ahead and so on, the TCAS also triggers SOS (distress signals) from the locomotives as well as from nearby stations in emergency situations.

To enable this monitoring, RFID (Radio Frequency Identification) tags are attached to the tracks at the stations, blocks, points and signals and they are assigned unique Track Identification Numbers (TIN). These RFID tags are read by the TCAS system attached in the loco enabling it to determine the direction of the train. Next, the stations are provided with Stationary TCAS with radio towers to communicate with the locomotives in the area. They are interfaced with the station interlocking system to acquire real-time dynamic information of the signals.

The stationary TCAS units at stations get real-time information regarding locations, speed of the trains in its limit through UHF Radio Communication. Level Crossing Gates and Intermediate Block Signaling locations are provided with separate stationary TCAS if they are far from the coverage of station radio towers. Remote Interface Units are provided where remote signaling functions are required.

When it comes to functioning, the Kavach on the locomotive determines the location of the train by reading RFID tags and sets its location and direction. The movement is determined when the locomotive passes two RFID tags. After passing, it transmits location and direction to the stationary TCAS in stations using its UHF radio antenna. The stationary TCAS uses this information to find the approaching signal of the locomotive. Using these information as well as others, the stationary TCAS calculates the ‘Movement Authority’ (distance upto which the train is permitted to travel without danger) and the movement authority is transmitted to the locomotive. The length of the movement authority is decided based on the signal aspect of the approaching Stop Signal.

The stationary TCAS calculates the ‘Movement Authority’ (distance upto which the train is permitted to travel without danger) and the movement authority is transmitted to the locomotive

If the signal is red, the stationary Kavach communicates to loco TCAS reducing this movement authority to zero and if the loco pilot fails to act, the brakes are applied automatically to stop the train. The movement authority is also restricted if there are conflicts between signal aspects, point position or other problems. If two trains are detected by stationary TCAS in a block section moving towards each other on the same TIN, SoS command is generated to both the trains. When the trains receive this SoS command they would be halted by automatic braking. This SOS can also be transmitted from one loco to other locos in case of emergency.

A divisional office will have a networking monitoring system with a central server for the centralized monitoring of TCAS equipped trains and stations within the network. Before the era of advanced equipment, train crews followed British era norms. The guards of each train followed an approach called ‘Look Back’ to observe anything unusual in the opposite track and communicated with the guard of the passing train in that track with mere flags. They alerted the next stations if there were some anomalies in the track. When they realized that the stations were too far, they stopped the trains to raise the red flag or flares to suspend any train movement.

Also Read: Seven things railways can do to transform into the core of Budget’s PM Gati Shakti plan

The railway unions for long have been condemning the consecutive governments for diluting the safety norms and not paying enough attention to safety of trains. They have been vehemently opposing the deployment of contract systems in the safety category, not filling safety department posts starting from gangmen to loco crews, making these staffers work over time and ignoring the safety norms. No matter how superior the technology or equipment is, the hardcore railway men believe that the human attachment to railway duty is paramount for safety. When traveling in a train next time, pay attention to a gatekeeper or a couple of orange uniformed gang men observing the wheel assembly of the compartment. They are actually looking for any flaws in the rolling stocks because a watchful eye can save hundreds of precious lives.

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