Interlocking System in Indian Railways

• 13 Jun 2023

Why in News?

An investigation is underway to determine the cause of a devastating train crash in Odisha's Balasore district. The incident has raised concerns about the electronic track management system used by the railways.

• The Indian Railway Minister has highlighted a change in the electronic interlocking as the primary factor leading to the accident.

What is an Interlocking System in Indian Railways?

• About:
  • Interlocking System refers to a crucial safety mechanism used to control train movements and ensure safe operations at railway stations and junctions.
    • It is a complex network of signals, points (switches), and track circuits that work together to prevent conflicting movements and collisions.
  • Electronic Interlocking (EI): It employs computer-based systems and electronic equipment to control signals, points, and level-crossing gates.
    • Unlike conventional relay interlocking systems, EI utilises software and electronic components to manage the interlocking logic.
    • EI ensures the synchronisation of all elements to facilitate uninterrupted train movement.
  • As of 2022, 2,888 stations in India were equipped with an electronic interlocking system — comprising 45.5% of the Indian Railways network.

Indian Railways Network

• The Indian Railways is the world's fourth-largest railway network, carrying an average of eight billion passengers annually.
• The network spans over 68,000 km and encompasses more than 7,000 stations, with a running track of 1,02,831 km.
• As of March 31, 2022, the total track length, including sidings, yards, and crossings, stands at 1,28,305 km.

• Components of Electronic Interlocking:
  • Signal: Signals use light indicators to direct trains to stop (red), proceed (green), or exercise caution (yellow) based on the track's status ahead.
  • Point: Points are movable sections of tracks that enable trains to change lines by guiding the wheels towards a straight or diverging path.
    • Electric point machines lock and unlock point switches in the desired position.
  • Track Circuit: Electrical circuits installed on tracks detect the presence of a train between two points, determining the safety of train movement.
  • Additional Components: Electronic systems, communication devices, and other equipment control signalling components and are housed in relay rooms with dual-lock access control.
    • A data logger records all system activities, serving as a record similar to an aircraft's black box.
• Functionality of the System:
  • Command Reception and Route Setting: The electronic interlocking system receives commands from operators or automated control systems following which information is collected from the yard and processed to set a safe route for trains to follow.
  • Alignment and Interlocking: Once the route is determined, the system aligns the necessary track switches (points) and interlocks signalling devices at appropriate positions to establish the desired route.
  • Signal for Train Proceeding: Trains are given signals to proceed based on the track's direction and the absence of obstructions on diverging tracks.
    • This ensures that trains can safely and smoothly navigate through the network.
  • Collision Prevention: The system utilises track circuits to detect the presence of trains.
    • By monitoring these circuits, the system prevents multiple trains from running on the same block or conflicting paths, thus minimising the risk of collisions.
  • Point Locking: Points (switches) remain locked in position until certain conditions are met, such as the train crossing a specific section of the track or the signal to proceed being withdrawn.
    • This ensures that the points are correctly aligned and secure for train movements.
  • Failure Indication: In the event of a failure or malfunction, the system alerts operators or maintenance personnel.
    • One common method is the use of a red light signal, indicating that the system has detected an issue and the route ahead is not clear or safe.
    • This prompts appropriate actions to be taken to resolve the problem and ensure safe operation.

Source: TH