Signals, systems, checks, balances: Explaining the Odisha train disaster

The Indian Railways is deploying a new train control system, as pressure on its infrastructure increases

The railway line near the Bahanaga Bazar station in Balasore was being repaired hours before the Coromandel Express passenger train passed through on June 2. The railway line or section is one of India’s busiest, serving freight trains lugging coal and iron ore from Jharkhand to ports like Odisha’s Paradeep and those in the south.

The section’s train management is fully computerised with a key role played by the electronic interlock, a term that became news after a multi-train crash involving the Coromandel Express killed more than 270 people and injured over a thousand.

In the past few years, the Indian Railways has been deploying the Centralised Traffic Control (CTC) system to replace the older Control Office Application (COA). The two systems sit at the heart of a rail network that manages signaling of interlocked regions where multiple passenger and freight trains run through.

The computerised Centralised Traffic Control system has been applied in two new stretches: Ghaziabad-Kanpur in Uttar Pradesh and in the Bhadrak-Dhamra stretch of Odisha where the crash happened last week.

Managing trains

Over decades, the job of sending a train on its way has gone out of the hands of station masters and their staff. Bahanaga Bazar station is in the South Eastern Railways zone that handles 14 per cent of India’s originating railway freight traffic. Each zone is split into divisons. To manage passenger and freight trains running across 363 stations of this zone, the Railways has a system of offices known as Section Controllers. The Section Controllers manage routes in each of these divisions, which are the basic structure of the Railways' operating control

Air Traffic Controllers, from their towers, can see an aircraft on the ground. A railway Section Controller has no visibility-based controls and relies instead on a two-way telephone system called an omnibus circuit. It permits all stations to directly communicate with a Section Controller, who in turn can speak to all stations at once or to one station. Unlike aircraft pilots, the train driver plays no role in these communications. Acceleration, deceleration or stoppage of trains is decided by the signaling system. The movement of trains is plotted on a time distance graph to record actual progress. (See visual)

Visual display wall at Station Controller that displays track layouts of stations with real-time status of track circuited lines. The panel also provide alarm indications of failure of points, signals, track circuits etc

Officers and staff from technical departments have a representative in control offices to provide support. It is a large establishment that is at work all the time across the country’s rail network. At any moment, there are 50 types of operations that these offices undertake in real time. All trains and rakes are provided with an alpha-numeric mark called a train describer tag. (see table)

Of late, the demand for track renewals has risen as large freight trains carry minerals to all over India. These rakes put heavy pressure on tracks, which need careful upkeep. As the economy gathers pace after the pandemic, the demand for minerals has shot up and so have the number of cargo trips. The Railways, in the current financial year 2022-23 an average of 410 rakes per day to power plants, up from 380 before the pandemic.

When a rail track needs to be blocked off for repairs, as it possibly happened on June 2, the request comes to a Section Controller office, which carves out a suitable slice of time. Train speeds are changed accordingly.

As a matter of precaution, the signaling system in overhead wires and the interlocking rails are calibrated to move simultaneously. It is not possible for a rake or a train to get clearance for a journey from the signals unless the rails below have also been arranged accordingly. A range of officials work on the systems to generate data for each other, so no observation, even a minute one, goes unnoticed. In the older system there was a route relay interlocking that shut down the section totally when a block operation i.e. repairs were on. The new CTC system runs the same rule with one exception, the block or shutdown of the section is not total.  

Yet, just conceivably, two things may have happened on June 2, said a former member traffic of the Railways board. As train speeds increase, this block of repair time is getting squeezed. It is possible that the signaling system switched on but the interlock did not, said the former official. A Railways manual notes the Centralised Traffic Control facilitates the train control and management of multiple signaling interlocked regions from a “single location”. “The computer based Interlocking gathers the required static and dynamic information from the track side signalling gears and sends it to the central server(s) located at a distant location by means of optical fiber”. This information is then used to provide the real-time simulation of railway traffic on the tracks.

Is it possible?

The Centre for Advanced Maintenance Technology (Camtech), a research and consultancy arm of the Railways in Gwalior, carried out tests in Ghaziabad-Kanpur and Bhadrak-Dhamra sections. It noted that sometimes CTC, the new system, was not used by Section Controllers due to a different concept than COA. It is "difficult for Controllers to work in two different systems ie CTC and COA,” said Camtech’s report.

The report noted that since there shall be frequent changes across sections in a CTC territory of close to 400 route km, those need to be “incorporated in the CTC software immediately to prevent blackout of that particular section. Needs continuous monitoring and feedback from all the units working in the section”. Unstated is that these blackouts obviously mean trouble for the Station Controller who pushes back for the older system.

Again, what are the possible reasons for such blackouts? The report noted that at many stations, the computers did not get the feed or suffered a blackout for “5-10 min. even when there was a single fiber cut, as all stations (are) connected serially via IP Networking”.

Camtech has suggested, after observing the working of Station Controllers in the two pioneering stretches, to integrate the new CTC data with the older COA data. “It can solve the above issues as (various) applications can fetch data from COA and not CTC train graph”.

Based on initial observations, conceivably there was a moment when the signal came on but the electronic interlock failed to respond on June 2. These interlocks also run on the same bank of optical fibre cables as the ones that provide the display of information at the stations. It does not seem feasible given the huge range of redundancies and repetitive checks built into the systems.

To avoid train accidents, remote monitoring of signaling equipment at stations and where there is a live block is provided on the terminals of Centralised Traffic Control offices. This includes logging in of events in the central system, generating alarms and alerts. A failure of signaling equipment is an alarm for the engineer posted there who also decides on the category of alarms.

Despite these checks and balances, the three-train crash still occurred.

Train Control responsibilities of Station Controllers

1. Monitoring movement of trains from station to station and recording paths and detention on charts

2. Arranging crossing and precedence of trains judiciously.

3. Arranging working of departmental and material trains.

4. Giving time signal to all stations on the section daily at appointed time

5. Fulfilling interchange commitment.

6. Arranging proper movement of assisting/banking /light engines.

7. Clearance of sick wagons from Roadside stations.

8. Arrangement of relief for 10 hrs duty staff.

9. Incident management on rail network & at station

10. Arranging Engineering and/or power blocks in such a way as to involve minimum disturbance to train running.

11. Maintaining fluidity of yards by controlling the flow of stock in and out of yard

12. Arranging Speedy relief in case of accidents

13. Collecting information from the various stations on the section in respect of – (i) Registration for wagons outstanding at stations and arrangements for supply of wagons. (ii) Number of wagons loaded and empty wagons/rakes awaiting despatch.

14. Arranging running, regulation, putting back and cancellation of trains.(both freight & coaching

15. Securing maximum loads for trains.

16. Collecting stock position from the different stations, marshalling and terminal yards.

17. Arrangement of Crew & Guard for freight trains

18. To keep liaison with adjoining Railways and Divisions for interchange commitments

19. Monitoring and coordinating working of yards, goods sheds sidings, loco-shed, TXR depots etc

20. Supervising of stock control.

21. Arranging supply of wagons against pending registration.

22. Securing optimum utilisation of stock, with minimum detention.

23. To ensure optimum utilisation of loco and staff. [

24. To arrange ART & Crane from adjoining Railway/Division in case of accidents and other coordination

25. Requisitioning engines from loco sheds for all operating requirements, i.e. Train working, Shunting and Banking.

26. Ensuring most economical use of engines by close supervision both in Traffic Yards and sheds

27. Ensuring the return of engines to “Home Sheds” at regular intervals for servicing and maintenance.

28. Ensuring an even balance of engines and crews between running sheds for meeting demands of traffic,

29. Ensuring that light engine kilometres is kept to the minimum.

30. Providing guidance to running staff for troubleshooting.

31. Ensure timely examination and fitness of all trains

32. To keep a watch over the detachment of sick wagons/coaches and to arrange for their early repair and fitness.

33. Keeping a watch over availability of vital C&W components, like Air Hoses, Washers, Clamps etc.. and efficient working of equipments & machines in C&W depot to avoid detention to trains.

34. To keep a watch over placement of wagons/coaches in sick line and their release.

35. To keep account of detention to trains on C&W account and take remedial action.

36. To provide guidance to running staff for trouble shooting.

37. For Electrical Multiple Units, this function is performed by Traction Loco Controller(TLC)..

38. Monitor the movement of POH due stock to workshops

39. To expeditiously dispose off unclaimed and unconnected wagons, parcel consignments.

40. To keep a watch on detention to trains on Commercial account like Alarm Chain Pulling, Carriage watering, Parcel working etc., and take remedial measures.

41. To ensure quick transhipment of sick wagons by arranging matching stock and labour.

42. To keep a watch over submission of station returns.

43. Monitoring of public complaints lodged at the stations.

44. To ensure proper maintenance of public amenities available at stations.

45. Any other job entrusted by Sr. DCM/DCM.

46. Arranging maintenance blocks for OHE

47. Arranging alternative power supply in case of tripping etc., through remote control.

48. Monitoring OHE failures and taking remedial action.

49. Monitoring detention of trains on OHE accounts.

50. Guiding running/ station staff in trouble shooting