Bengaluru: On 2 June, a collision involving three trains near Odisha’s Balasore district led to the death of 275 people and left over a 1,000 injured. The accident, the worst India has seen since 1995, has brought to attention the various aspects of security in Indian Railways, especially the new collision protection system called ‘Kavach’, which is in the process of being rolled out nationally.
Domestically developed, Kavach is a form of ‘Traffic Collision Avoidance System’, or TCAS (pronounced ‘tee-kas’), designed to prevent two vehicles from colliding. In order to do this, the system detects the distance between the vehicles and the rate at which it changes.
TCAS has been widely used in aircraft to reduce mid-air collisions since the early 1980s. In 2019, a mid-air collision between a Boeing and an Airbus over Mumbai airspace was averted due to the activation of TCAS, said media reports, enabling one of the planes to immediately climb higher.
Similarly, the Kavach system detects the proximity between two trains, moving head-on towards each other on the same line, and automatically applies brakes. It also alerts the operator or loco pilot to take control of the train.
ThePrint explains how Kavach works and whether it could have prevented the Odisha tragedy.
Also read: Just 2% of India’s rail track covered by Kavach, tech that ‘could have prevented Odisha tragedy’
What is Kavach
Kavach, Hindi for armour or shield, is one of the higher safety level systems — Safety Integrity Level 4 (SIL-4) — that are being deployed by the Indian Railways to improve safety in train operations and achieve the gold standard of zero accidents yearly.
The Kavach system has been designed by the Research Designs & Standards Organisation (RDSO) of the Ministry of Railways. It comprises on-board equipment on locomotives, track-side elements, and the wireless network it operates on.
Its primary objectives are to avoid collisions and to turn on the braking system when safety parameters are exceeded — such as before an impending collision or when a pilot jumps a red light, or when the maximum speed limit permissible is exceeded.
Furthermore, it is also expected to aid with emergency SOS messages, auto whistling while approaching level crossing gates, and reduction of speed to 30 km per hour when the locomotive enters loop lines.
India also has a Kavach antimissile system that has been in operation since 2012, and the TCAS system has adapted technology from this as well.
How does Kavach work?
The Kavach system has features that display information like speed, location and distance to signal ahead, type of signal, distress messages from pilot or station, and more.
The tracks contain radio-frequency identification (RFID) tags that are fitted on each section of a track and provide information directly to the Loco (locomotive) TCAS unit inside the train. Different segments of the track are assigned unique IDs, and these determine the direction and speed of the train.
There is also a Stationary TCAS unit installed at stations with a radio tower to communicate with nearby locomotives. Inside a locomotive, there are sensors placed at the front end and rear end, the top, and also on some wheels.
When a train passes two RFID tags sequentially, its direction and speed can be determined. As a train passes a segment, the Loco TCAS unit sends information about the train to the Stationary TCAS unit installed at the station via ultra-high frequency (UHF) radio antenna.
When an approaching signal is red, the Stationary TCAS will relay the information to Loco TCAS, slowing down and stopping the train. If the loco pilot is unable to do so, automatic brakes are applied.
When there is any conflict between signals from various sources or sequences, the Stationary TCAS unit will apply the most restrictive conditions and reduce movement of trains accordingly.
When two locomotives are moving towards each other on the same track, SOS signals are sent to both trains from the station along with visual and audio warnings to the pilots, automatically stopping them both.
Depending on the speeds of the train and the distance between them, the Kavach system activates to ensure a safe distance of at least 300 meters is maintained as both trains come to a complete halt.
There is also a centralised monitoring of TCAS systems being planned, along with a number of other failsafe and backup security systems that will be put into place to avoid collisions, according to an official document on the Kavach system released by the Indian railways.
“Currently about 2,000 km is [to be] covered in 2022-23, around 34,000 km of network that lies in the high-density corridor will be brought under Kavach in a phased manner first,” said Vivek Kimbahune, executive vice-president of Bengaluru-based Saankhya Labs, that has supplied satellite communications solutions for real time tracking of trains. The real time train tracking information on the National Train Enquiry System (NTES) available on tracking websites is due to this satellite communication network.
“The weak point of the Kavach system is that it is fully functional and advantageous only when the entire railway network is enhanced, with all locos equipped with Kavach,” he added.
Additionally, it is also possible to integrate Kavach with satellite communication, providing real time updates and ease of transmission of signals.
Also read: ‘Your govt finding diversionary tactics’—Mallikarjun Kharge to PM Modi on Odisha train accident
Could Kavach have prevented Odisha collisions?
In the Odisha collision and derailing, three trains were involved. The collision was brought about by a wrong track change leading to a collision and derailment of all trains.
“Odisha accident was a rare accident…. If there had been a 30-40 seconds delay, the last three bogies of the Bengaluru-Howrah express would have cruised through safely. The derailed bogies of Coromandel Express hit the Bengaluru-Howrah express, which was unfortunate,” explained Kimbahune, who had worked very closely with the central government for the Centre for Railway Information Systems (CRIS) during implementation of satellite communication (satcom) tracking in trains.
He added that the disaster could not have been averted with Kavach since the system cannot prevent derailment. Additionally, both trains moving towards each other needed to have been equipped with Kavach for the system to function, but neither were. The trains were also running within permissible speed limits, which would not have triggered the brake activation.
But, most importantly, the mainline signal was green for both trains, but the Coromandel Express got diverted into a loop line where a stationary locomotive was resting. Kavach is not designed to detect and act on interlock malfunctions or changes in track alignment.
Lastly Kavach requires a minimum distance for slowing down before a locomotive comes to a complete stop, said Kimbahune. In the case of Odisha, given the speed and distance on the loop, it would have been impossible for the loco pilot to react or for the system to automatically bring the train to a halt safely.
However, Kimbahune added that until full investigation is completed, most guesses as to the cause of the accident and how it might have been prevented are within the realms of speculation.
When will Kavach be implemented?
Work on Kavach began in 2012, and the first field trials were carried out in 2016, followed by active development since 2017.
A live demonstration took place in March 2022 in Secunderabad. The Indian railway minister Ashwini Vaishnaw was seated in one moving locomotive, while CEO of the Railway Board, Vinay Kumar Tripathi, was seated in another. Both trains were heading towards each other on the same track.
The Kavach system was tested successfully when it automatically deployed brakes, bringing the trains to a halt.
Today, the system is deployed in 65 locomotives and 134 stations. As of December 2022, 1,455 km of tracks have been covered under Kavach.
Presently, implementation of the system is in progress in Delhi-Mumbai and Delhi-Howrah corridors making up 3,000 km. The entire system is expected to be operational by FY 2027-28. When completed, it will be the world’s most inexpensive automatic train collision system, costing Rs 50 lakh per km as compared to Rs 2 crore per km worldwide, stated the Ministry of Railways in a release.
(Edited by Zinnia Ray Chaudhuri)
Also read: Problem with interlocking ’caused Odisha tragedy’. What is this key part of signalling system