Automatic train control and signaling for high-speed rail

India runs one of the world's cheapest automatic train protection systems, built entirely at home — yet the one line where trains will run at 350 km/h uses signalling shipped from Japan.

That is the shape of the gap. India has an indigenous train-control system, Kavach, and it has scale. What it does not yet have is an Indian system certified to protect a true high-speed train.

A high-speed signalling system is a hard thing to build because it is safety-critical software of the most unforgiving kind. Above roughly 120 km/h, a driver can no longer read trackside signals in time; the system must display movement authority, target speed and signal aspects inside the cab, and brake the train itself if the driver does not. That logic must be certified to Safety Integrity Level 4 (SIL-4) — the highest railway safety grade — under the European CENELEC standards, and independently signed off before a single passenger boards.

India has climbed most of this mountain on conventional track. Kavach, developed by the Research Designs and Standards Organisation (RDSO) with Medha Servo Drives, Kernex Microsystems and HBL Power Systems, began in 2011 as the Train Collision Avoidance System, ran its first passenger-train trial in February 2016, and earned SIL-4 certification in 2019. It was adopted as the national ATP standard in July 2020. Version 4.0, approved on 16 July 2024, added location accuracy, optical-fibre links between stations and direct interfacing with electronic interlocking. It is now commissioned on 1,452 route km of the Delhi-Mumbai and Delhi-Howrah corridors, with bids out for roughly 15,000 route km. At about ₹50 lakh per route kilometre, it is among the least expensive ATP systems in the world.

The country has also gone further on radio-based control. The National Capital Region Transport Corporation (NCRTC) put ETCS Level 2 — combining automatic train protection, operation and supervision over radio — into service on the Delhi-Meerut Namo Bharat corridor, and in October 2023 achieved the world's first real-traffic deployment of ETCS Hybrid.

But the 508 km Mumbai-Ahmedabad corridor, India's only true high-speed line under construction, is being built with Shinkansen rolling stock, signalling and design standards transferred from Japan, with a 350 km/h design speed. Its signalling is reported as ETCS Level 2 capable of high-speed operation, with contracts already awarded. The technology transfer is structured to support Make in India, but the certified high-speed stack itself arrived from abroad.

Why the gap persists is structural rather than a matter of will. Kavach is certified for conventional and semi-high speeds, not for 250-350 km/h. A high-speed train-control system cannot be validated in isolation: it must be integrated with and proven against the specific high-speed trainset it protects, and India has no indigenous 250-350 km/h trainset. The certification chain is also not yet fully domestic — when Kavach in the Agra division was independently assessed in 2024, the accredited safety assessor was Italian. Independent safety assessment capacity at SIL-4 remains an emerging capability.

What it would take is visible in the dependencies India already holds. The interlocking, radio backbone, positioning and optical-fibre layers are in production. The supplier base is widening beyond the original three OEMs — Concord Control Systems has RDSO prototype clearance and is completing SIL-4 certification, with Quadrant and Digitronics being positioned to add capacity. The missing pieces are a high-speed trainset to validate against, a train-control design proven at 350 km/h, and domestic independent safety assessment. The foundations are laid; the summit — a certified, Indian high-speed protection system — is the part still ahead.