DT Next Explains | What is Kavach?

CHENNAI: Over the past year, Tamil Nadu’s railway network has taken a major step towards enhancing passenger safety with the launch of the ‘Kavach’, an automatic train protection system.

Nearly a year ago, Tamil Nadu began installing a one-of-a-kind sensor controlled train protection system called Kavach on a few of its frequently used rail routes. Cut to the present, the 160-km stretch between Chennai and Renigunta is fully operational while work is in progress on the Chennai–Vijayawada and Chennai–Coimbatore stretches.

According to experts, for 2 million passengers who are patrons of the Southern Railway on a daily basis, the new system promises a drastic reduction in the risk of collisions. However, not many understand how the system works to ensure safe passage for trains.

The word ‘Kavach’, which literally translates to protection, is an automatic train protection (ATP) system developed by the Research Designs and Standards Organisation (RDSO) in collaboration with the Indian railway industry.

Kavach is designed to enhance safety by performing two important functions. First, it prevents a train from jumping a red signal, a failure railway engineers refer to as ‘Signal Passed At Danger’(SPAD). Second, it ensures that the train never exceeds the speed limit on a given stretch of track.

Experts point out that a train moving at 100 km/h speed takes at least 1 kmto come to a halt which does not give the loco pilot the luxury of responding at the last moment. While fatigue, fog or a momentary distraction can turn a missed signal into a fatal collision, Kavach is designed to catch that lapse before it becomes irreversible.

Surprisingly, for a sophisticated automated system, Kavach does not depend solely on GPS to track trains. It may be noted that railway engineers who tested an earlier system called the Anti Collision Device (ACD) found that GPS was extremely error-prone for moving trains and it could not tell for certain whether two trains were on adjacent tracks or the same track, leading to frequent application of brakes to avoid accidents.

However, Kavach uses a more old school but reliable method in which RFID (Radio Frequency Identification) tags are fixed on every kilometre of the track. Each tag carries the exact location and also the distance to the nearest station. Owing to this, two tags placed a few metres apart allow the system to determine the direction in which the train is travelling.

Similarly, the trains are fitted with an RFID reader and speed sensors on its axles. By reading a tag and continuously measuring the wheel rotation, the computer onboard calculates the train’s exact position until it encounters the next tag. Experts note that this method keeps errors considerably low and aids the loco pilots to be well informed of the various signals on the route along with the speed restrictions.

However, knowing the exact location of the train solves only half the problem, as Kavach also needs to know what is displayed at the next signal junction and details of the speed limits that are ahead. All this information comes from what engineers call the station kavach, which is a small computer installed at stations and track-side locations.

The station kavach collects data from signal poles, track switches and a central server at the divisional headquarters that issues temporary speed restrictions. It then transmits this data wirelessly to the trains where inside his cabin, the loco pilot can see information about the next signal, current speed and any upcoming restrictions on a small display.

If the pilot does not slow down in time for a red signal, Kavach would first issue a warning followed by an instruction and finally, at the very last moment, it would automatically engage the brakes. While the pilot remains in control of the train, Kavach is designed as an assistant that stays alert to avoid accidents that can happen due to man-made errors.

As of last month, Kavach has been deployed over 1,500 km across the country, mainly in the South Central Railway route and currently, in Southern Railway routes. In Tamil Nadu, Kavach is fully operational in the Chennai-Renigunta route (160 km), and in the Chennai-Vijayawada route (430 km), pilot is completed and rollout process is under way.

According to the Southern Railway, these sections will be fitted with the safety system soon: Chennai–Vijayawada, Chennai–Coimbatore, Coimbatore–Mettupalayam, Madurai–Kanniyakumari, and Thoothukudi–Tirunelveli–Madurai.

TN has over 3,800 route km of railway track and once Kavach is fully deployed, it is expected to considerably eliminate the risk of rear-end and head-on collisions. Most importantly, the fatigue and exhaustion experienced by the loco pilot will come down considerably.

Since Kavach allows signals to be placed as close as 1 km apart, more trains can run on the same track without compromising safety which will result in the increase in average speed of the locomotives. Apart from this, freight trains on industrial corridors like Chennai–Thoothukudi can ply more efficiently once they get the automated safety system.

Advantages of installing Kavach

• On-board loco devices can continuously monitor train speed and movement

• RFID tags on tracks help monitor movement and communicate information to trains

• Stationary towers and locomotive-mounted radios for real-time data exchange

• Automatic braking if speed limits are exceeded or a signal is passed at danger