Despite accidents being a recurring issue due to its decades-old signalling system, the Indian Railways does not seem to have learned its lesson. About one year and four months after the Balasore train tragedy in Odisha, another accident occurred at Kavaraipettai near Chennai, putting the country on edge. Like the previous one, this latest incident resulted from faults in the signalling system. In the Balasore accident in June 2023, a total of 296 people were killed when the Coromandel Express collided with a goods train and the Howrah-Bengaluru Express. Many lives were also lost when the Kanchenjunga Express derailed at Singur in Bengal, again due to signalling failure. Trains often narrowly escape disasters related to signal failures and snapped signal cables.
Electrification, signals, and track infrastructure are critical for train transport. While electrification and track modernization have progressed significantly, the signalling system remains outdated. Although plans for automatic signalling reforms on the lines of the metro rail systems were proposed, they have not progressed much. Let’s explore how the ageing railway signalling system operates and its various functions.
How Railway signals work
Trains nationwide are directed to follow specific tracks, with signals and tracks prepared simultaneously. A railway track is connected to another track via movable pieces of rail known as points, which are controlled by a mechanism called a point machine. These machines are typically located about one metre from the rail at the same height and are often seen near railway stations. An electric motor inside the box moves the tongue rails to change the rail path. When the station master selects a particular route from the panel board in his room, the points move accordingly, and signals are displayed. Technical systems such as panel interlocking, route relay interlocking, and electronic interlocking are used to set the routes.
Flags and torches
During railway journeys, station masters, guards, and loco pilots frequently wave flags and torches. The railway staff's red and green flags are important signals in train operations. Even if a green flag signals the train to proceed, it does not move if a red flag is raised by any of the railway staff. Flags are used daily, while LED torches replace them at night. Another important signal is the detonator, used by track personnel, loco pilots, and guards.
Signals for departure and shunting
The signal indicating a train's departure from a railway station is called the starter. Once all tracks converge on the main line, another signal, known as the advance starter, is given. At some larger stations, there may be an additional starter signal between these two. The last starter signal seen is the last stop signal at that station. In addition to red, yellow, and green signals, white signals can also be found on small posts within railway stations. These are shunt signals and are used solely for operations within the station premises.
'Kavach' in the limelight
Whenever there is a train accident, media discussions emphasize the urgent need to implement the Kavach system across the country's railway network. Kavach is a safety system designed to prevent collisions between trains. It is an automatic train protection system aimed at avoiding such incidents. Introduced by Mamata Banerjee, the Railway Minister in Manmohan Singh's Cabinet in 2011-12, the system was later renamed the Collision Avoidance System (Kavach) under the first Modi government in 2014.
In 2019, three companies received permission to construct and install the system, which was successfully tested in 2022. When two trains are approaching on the same track, and the loco pilot cannot control the speed, the Kavach system automatically activates the braking system within a specified distance. This is made possible through radio technology and GPS. A train approaching another on the same track will automatically stop at a distance of 380 metres. However, due to the government's failure to install the system on all railway routes, the potential benefits of Kavach have not been fully realised.
What Kavach does
The Kavach system accurately monitors train movement and automatically sends messages regarding appropriate emergency responses.