Kavach, the TCAS, is big, really big!

 

The system of Signalling on Indian Railways(IR) India is based on the conventional Absolute Block System, which in simple terms, means that in a block section between two stations, only one train can be permitted. Since this imposes serious restrictions on line capacity, Automatic Signalling is provided in suburban areas which has a signal every kilometre and therefore larger number of trains can be operated in the section. These systems depend entirely on the vigilance of the driver to sight the signals and run the train accordingly and is, therefore, prone to human error. The issue of upgrading the systems to have an intelligent system, which can alert the drivers about the signals and route parameters ahead, and override any erroneous action or inaction by them, has been under consideration for decades.

 

The Signalling systems in countries with developed railways have advanced to systems with significantly-reduced human element. In Europe, since trains cross from one country to another frequently, the European Train Control System (ETCS) for Signalling and train control component was developed as a standard system in nineties as a uniform system for all countries with Standard Gauge tracks; it provides for interoperability, superimposed on the incompatible systems in various countries. Its first fully-developed version, ETCS-Level 1, used track-side radio transponders, called Balises, to transmit signal aspects as movement authority, in the form of Cab Signalling for the driver, together with route data, at fixed points to a matching receiver on the vehicle. The on-board computer on the vehicle oversees and controls the speed and braking from these data, overriding the driver if the permissible speed is exceeded. Because of the spot transmission of data, the train must pass a balise to obtain the next movement authority. 

The next version, ETCS-level 2 is a GSM-R or GPRS radio-based system which displays Signalling, route data and movement parameters in cab through continuous exchange of information, including  its position and direction, with a Radio Block Centre (RBC), which also  oversees and controls the train movement over the entire section. Balises and other track-side equipment like axle-counters are still used, the former as passive positioning beacons as a reference for on-board equipment like odometers and radar and the latter to confirm train integrity. Although less expensive alternates to Balises are available, they continue as a legacy since most of ETCS-level 2 installations are an upgrade of Level-1. ETCS Level 3 is a futuristic system which does away  with trackside equipment totally. The RBC receives positioning of each train continuously and calculates smallest possible train distances at any time., with the train control not based on fixed blocks but broken into moving blocks, with the train itself being a block, i.e.,  there is a real-time determination of the point on the route the entire train safely clears and the following train can be granted an authority to move up to this point. While Line-capacity goes up with ETCS-level-2 considerably, ETCS-level-3 would take it to a theoretical maximum. ETCS-level-3 has, however, not been installed commercially as yet.

 

IR has pursued modernising its Signalling systems mainly by converting its Panel Interlocking to Solid State Interlocking (SSI) and installing Route Relay Interlocking (RRI) at major station yards. It has also tried out in dribs and drabs systems which are roughly akin to ETCS-level-1, like Automatic Warning System (AWS), which alerts the drivers with an audio-visual indication of the signal status and brakes if the driver fails to acknowledge it and Train protection and Warning System (TPWS),  which applies the vehicles brakes when the vehicle passes an active ground transmitter and fails to reduce speed or stop at a caution or stop signal respectively.

 

The first significant initiative was mooted by Konkan railways in early 2000s with Anti Collision Device (ACD), an electronic non-signalling system, basically to eliminate collisions due to human errors. It calls for a network of onboard devices for cabs and Guard vans and track-side devices at stations and Level Crossings. All the devices along the route communication to each other through radio when they are within a radial range of around 3 kms. On board computers use inputs from GPS for determination of train location, speed, course of travel and time. The system was tried out extensively on the NF Railway with moderate success as large-scale nuisance overrides caused slowdown of train operations.

 

But a big issue was that ACD was a black-box for IR, with the IPR resting with a lone vendor who was unwilling to share it with IR. Around 2008, Indian Railways decided to develop multiple vendors of ACD renaming the systems as Train Collision Avoidance system (TCAS). As the lone vendor of the system was not forthcoming to take it forward, some bold engineers of Research, Design and Standards Organization (RDSO), Lucknow, the R&D unit of IR, mooted a change in the philosophy, committing themselves to move far beyond a simple anti-collision system and to develop a modern Signalling system with features similar to ETCS-level-2, with provisions of, inter alia, Distance to Go Signalling, prevention of Signal Passing at Danger (SPAD), Cab Signalling, speed control, Line-Capacity friendliness and enhancement capabilities; Distance to Go Signalling is one level below full ‘moving block’ Signalling of CBTC, with the track divided into many block sizes and movement authority of the train is up to the last possible block-end before the tail of a preceding train. It presents to the driver the distance to go before, and the braking speed curve till, the desired point of Stop, and itself acts on it if required. While prevention of collision, which essentially takes place due to SPAD at some stage, is automatically prevented, the system retains the capability to avoid side-collisions too. The rest, as they say is history.

 

In spite of stiff opposition from the champions of ETCS-level-2 and those who had sights on a lower grade system like ACD, these engineers worked diligently on TCAS in the period 2011 to 2016. In this period, and even later, like Vande Bharat express project, there were deliberate delays to stall the project by certain vested interests and even sneers from regressive elements who would have been satisfied with an ACD-equivalent. The current status is that it has been proven, on a long stretch on South Central Railway, to be a versatile Signalling system which would meet the needs of IR for decades to come.

 

The Minister, Ashwini Vaishnaw, has gone and tested the system himself to send a message that the days of venal delays and procrastination are over. A significant transformation of Signalling system of IR is now round the corner.

 

The ballpark expenditure on the system would be in the range of Rs 40 to 50 lacs per route kilometer against Rs 2 crores for ETCS-level-2. To convey that the system is far more than the limited scope of anti-collision, it has been rightly christened as Kavach (shield).

 

This success needs to be celebrated as it has the promise to save thousands of crores for the country. The engineers who worked on the project should be suitably recognized and felicitated to inspire the engineers of a largely-status-quoist IR to emulate them in the field of railway engineering.