Kavach in Indian Railways – Laying OFC Along the Track

Updated: 23 October 2026

What is Kavach in Indian Railways?

Kavach is the automatic train protection (ATP) system developed for Indian Railways through RDSO, its research and standards organisation, working with Indian industry. The word means armour or shield. The project began life as the Train Collision Avoidance System, or TCAS, and was later renamed.

Its job is to step in when a human error could cause an accident. According to PIB, the Kavach system protects against three main dangers: a train passing a signal at danger, a train running faster than permitted, and collisions. If the loco pilot does not respond in time, Kavach applies the brakes itself.

Key milestones published by PIB:

• field trials on passenger trains began in February 2016;
• Kavach was adopted as the national ATP system in July 2020;
• version 4.0 was approved in July 2024;
• it is certified to Safety Integrity Level 4 (SIL-4), one of the highest levels used in railway signalling.

Rollout is now moving onto high-density routes, and every new section needs equipment on the ground, on locomotives and along the track.

How does the Kavach system work?

Loco Kavach

An onboard unit in the locomotive cab watches speed, receives movement authority and shows it to the loco pilot. It works out a braking curve and applies the brakes automatically if the train is about to pass a danger signal or exceed a speed limit.

RFID tags on the track

Tags fixed between the rails tell the passing train exactly where it is. That precise position is what lets the system calculate how much distance remains before a signal or a speed restriction.

Stationary Kavach

Units at stations collect live information from the station's interlocking, such as signal aspects and point settings, and pass it on to approaching trains.

Radio towers and UHF link

Trains and stationary units exchange data over secure UHF radio. Towers carry the antennas that give continuous coverage along the section.

Network management

Critical events are reported to a central network management system, so the railway can monitor how Kavach is performing in real time.

What changed in Kavach version 4.0?

RDSO approved Kavach version 4.0 on 16 July 2024, and it replaces version 3.2 as the standard for new sections. Official statements list these main upgrades:

• better location accuracy for the train on the track;
• more complete signal-aspect information in large station yards;
• a station-to-station interface over optical fibre cable, which makes the fibre route part of the protection system itself;
• a direct interface with existing electronic interlocking systems, so stationary units read signal and point data more efficiently;
• approval, in May 2025, for operation at speeds up to 160 kmph, which covers semi-high speed trains such as Vande Bharat.

Version 4.0 was commissioned on the Mathura–Kota section of the Delhi–Mumbai route in 2025. In September 2026 it entered service on 108 route km of the Malkajgiri–Kamareddi section in the Hyderabad Division of South Central Railway, the zone where the early field trials ran and where version 3.2 already covers 1,465 route km.

How is Kavach tested and certified?

Because Kavach can brake a train on its own, every supplier’s equipment passes a strict approval chain before use. RDSO sets the specification. The product then goes through an independent safety assessment carried out by an Independent Safety Assessor (ISA), who checks design, software and test evidence against the SIL-4 requirement. According to PIB, three suppliers were approved for version 3.2 in 2018–19 after this process.

Field trials follow on running lines, and the system is commissioned section by section once the zonal railway is satisfied. For fibre contractors the practical effect is close scrutiny of drawings, test results and route records, so an incomplete as-built or an untested OFC length can delay commissioning of a whole section.

Why does Kavach OFC matter so much?

Radio handles the link between train and ground, but the ground equipment itself has to be tied together. Kavach OFC does that work. Optical fibre connects stationary units, tower radio equipment and the network management system with high capacity and immunity to electrical interference, which matters on a line carrying 25 kV traction.

A Kavach tower fibre connection is part of the same picture. Each tower needs a reliable link back to the station equipment, and fibre is the usual medium. Without a continuous, healthy fibre route, the system loses the data it depends on, which is why the cable is treated as safety-related infrastructure rather than a simple telecom line. Progress on this fibre is tracked nationally: PIB reported 4,960 km of OFC laid for Kavach by October 2024, and the ministry cited 5,856 km by July 2025.

The fibre also has to survive decades of track maintenance, drainage work and other cable laying around it. Where it runs, how deep it lies and how it is protected at crossings all affect its life.

How is Kavach fibre laid along the track?

Details vary with each railway's specification and the approved drawing, but the usual sequence looks like this:

1. Fix the alignment. The duct route is pegged within railway land, often in the cess or towards the boundary, keeping clear of the track structure, drains and existing cable routes.
2. Plan crossings. Places where the route must pass under the track, a road, a drain or a culvert are identified, and a bore or other method is chosen for each.
3. Trench or bore. The duct goes in by open trench on most lengths and by HDD where digging is not possible or not allowed.
4. Lay HDPE duct. Duct is laid, joined and sealed, with chambers placed at intervals for jointing and future access.
5. Install the fibre. Cable is blown or pulled through the duct, then spliced and terminated at stations and towers.
6. Test and mark. The finished link is tested end to end, and route markers are placed so the cable can be found later.

Steps one to three are where most damage to existing services happens, so they deserve the most care.

Why should a GPR route survey come before Kavach trenching?

The cess that suits a new duct is the same strip where signalling, telecom and power cables have been laid for generations. Cutting a signalling cable during Kavach work would be a bitter irony: a safety project disrupting train working. Ground penetrating radar finds cables, ducts and pipes, metallic or plastic, along the pegged alignment, and an EM locator traces conductive lines. Every service found gets a paint mark and an approximate depth before the trench is opened.

Our OFC route GPR survey is designed for duct lines like this, and the railway GPR survey service explains how track-side work is planned around blocks and railway rules. Crossings beneath the track get a separate scan of the bore path and both pits through our HDD route survey.

Fibre corridors are familiar ground for us. The 135 km OFC corridor in Bawana Industrial Area, delivered in 2019 for Bharti Airtel, is described on our Bawana project page. That was telecom work rather than railway work, but the route survey method carries straight across. For clarity, Mezux Touch has no link with Indian Railways, nor with any railway PSU; our reports are prepared for the fibre contractor or project owner who commissions them.

Which Kavach terms come up on site?

• ATP – automatic train protection, the class of system Kavach belongs to.
• SPAD – signal passed at danger, one of the main events Kavach prevents.
• Movement authority – how far a train may safely travel, sent from the ground to the loco.
• Stationary Kavach – ground equipment at a station linked to its interlocking.
• NMS – network management system, where critical events are monitored.
• Route km – length of route equipped, the unit in which progress is usually reported.

What records should a Kavach fibre route leave behind?

A fibre route is only as easy to maintain as its records. Keep the duct alignment against kilometre posts, depths at regular points and at every crossing, chamber and joint locations, and the existing services found during survey. Drawings showing the new duct alongside older cables save the next contractor from hitting either.

Planning a Kavach fibre package and need the route cleared first? Our railways sector page shows the full range of track-side survey work, and the quote form below takes your route file and block plan.