Indian Railways has commissioned version 4.0 of Kavach, its home-grown automatic train protection system, on South Central Railway for the first time. Announced on 23 September 2026, the upgrade covers 108 route kilometres of the Malkajgiri to Kamareddi section in Hyderabad Division. South Central Railway is one of the zonal railways of Indian Railways, the state-owned operator of the national network.
Automatic train protection, or ATP, is the class of system that sits behind the driver and intervenes when a train does something the signalling does not allow. Kavach, developed indigenously by Indian Railways, helps loco pilots hold the prescribed speed limit and brakes automatically if a critical situation demands it. Its central purpose is preventing a Signal Passing At Danger, or SPAD, where a train runs past a signal set to stop, and it is also meant to control speed in emergencies and keep operations safer in adverse weather.
The jump from Kavach 3.2 to 4.0 comes out of operating experience with 3.2, already working over 1,465 route kilometres of South Central Railway. Four improvements matter most: greater location accuracy for precise train positioning, better information on signal aspects in larger yards, station to station communication over optical fibre cable, and direct integration with existing electronic interlocking. Version 4.0 requires Safety Integrity Level 4 certification, SIL-4, the most demanding of the four integrity levels in railway functional safety, and Indian Railways intends it for large-scale deployment across the network.
Fitting Kavach to a section takes Station Kavach equipment at stations and in block sections, RFID tags along the track, telecommunication towers, optical fibre cable, and Loco Kavach equipment on the locomotives.
What the trackside tags actually do
The tags are the least glamorous item on that list and the one everything else leans on. A locomotive can measure distance travelled from wheel rotations, but odometry drifts: wheels wear, slip under power and lock under braking, and the error grows the longer the train runs without a fix. A system that does not know exactly where the train is cannot enforce a restriction that begins at a specific point, or tell whether a train is approaching a stop signal or has passed it. Each tag the reader passes over resets the onboard calculation to a surveyed location, and every braking and speed decision Kavach makes is built on that.
Under the Kavach specification issued by the Research Designs and Standards Organisation, RDSO/SPN/196, the tags are fitted to the sleepers between the rails and work in the 865 to 867 MHz UHF RFID band allocated for the technology in India. RDSO is Indian Railways’ own research and standards body. The tags have to read reliably at train speeds of at least 200 km/h.
Redundancy is designed in at both ends. Tags are duplicated at every location, carrying identical information apart from the absolute location data tied to that spot, so one damaged or unreadable tag does not leave a train without a position fix. On the locomotive, each Kavach unit has two RFID readers running in hot standby. The reader is mounted underneath the locomotive body and has to survive it: rugged against vibration, rated for speeds up to 200 km/h, and rated to at least IP65 outside the loco or IP64 inside. Few UHF RFID applications combine that read speed with that much mechanical abuse.
Three more sections inside seven days
Three further Kavach milestones landed between 19 and 24 September 2026, each with a published tag count.
The Jhansi division of North Central Railway, the zone covering parts of Uttar Pradesh, Madhya Pradesh and Rajasthan, commissioned Kavach on the Gwalior to Jhansi section, excluding Gwalior and Veerangana Lakshmibai Jhansi stations, and reported it on 23 September 2026. Some 1,596 RFID tags were installed to supply train identification and location information, and the system protects against head-on and rear-end collisions, roll-away and standstill situations. Jhansi divisional railway manager Aniruddh Kumar said: “The project was executed by Project Unit, Jhansi, with the active participation of the signal and telecommunications department and other railway teams.”
On Thursday 24 September 2026, North Central Railway commissioned Standard Kavach on the 52.46 km Agra Cantt to Dholpur section, with 720 RFID tags giving the system precise train location and operational data.
On 19 and 20 September 2026 the Solapur Division of Central Railway, another Indian Railways zone, ran the first Independent Safety Assessor audit trial of Kavach 4.0 on that zone. An Independent Safety Assessor is an outside party with no stake in the project, brought in to confirm a safety system does what it claims; this team came from Italy. The full-functionality trial ran on both Up and Down lines of the Kurduvadi to Boribial section, 104.7 route kilometres, with 1,430 RFID tags installed and programmed to the approved design and to standards prescribed by RDSO.
The scenarios validated make a useful list of what an ATP system is expected to do: SPAD prevention, including after a sudden signal put-back; permanent speed restriction and loop-line speed control; roll-away protection on a down gradient; automatic SOS generation when a train stops unexpectedly inside a block section; and manual SOS raised either through SMOCIP, the station master’s Kavach panel, or by the loco pilot on the onboard unit.
Between them, those three newly tagged stretches account for 3,746 trackside RFID tags: 1,596 plus 720 plus 1,430. Where the section length is published the density is consistent, at roughly 13.7 tags per route kilometre on both Agra Cantt to Dholpur and Kurduvadi to Boribial. That sets the arithmetic for a national rollout: every tag has to be surveyed, programmed with its own location data, fixed to a sleeper and kept readable under passing trains.
