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Electronic Interlocking System in Railways


An electronic track management system used by the railways has become the focus of investigations after the recent train crash in Odisha’s Balasore district.


GS III: Science and Technology

Dimensions of the Article:

  1. Interlocking System
  2. Electronic Interlocking (EI)
  3. Functioning of the Electronic Interlocking (EI) System

Interlocking System:

  • The interlocking system is a safety mechanism used in railway signalling systems to ensure the safe movement of trains on railway tracks.
  • It involves a controlled arrangement of signals and points, which are interconnected mechanically or electrically, or both.
  • The purpose of the interlocking system is to enable trains to move safely through a controlled area without conflicting with other trains.
  • The system ensures that train movements are coordinated and controlled, preventing collisions or other unsafe situations.
  • It allows trains to switch tracks or junctions securely, following a predefined sequence of movements that are regulated by the interlocking mechanism.
  • By using interlocking, the system ensures that conflicting train movements cannot occur simultaneously, enhancing the overall safety of railway operations.

Electronic Interlocking (EI):

  • Electronic Interlocking (EI) is an advanced signalling system used in railways that employs electronic components and software to manage train movements and track configurations.
  • The system ensures that two trains cannot occupy the same track simultaneously and allows a train to proceed only when the route ahead is clear.
  • EI is a modern alternative to the conventional Relay Interlocking system used in railway signalling.
  • Trained personnel from the signalling and telecommunications department, known as “signallers” or signal operators, operate and monitor the EI system.
  • The EI system consists of three crucial elements: signals, track circuits, and point switches.
    • Signals are used to communicate instructions to trains, indicating whether to stop (red), proceed (green), or exercise caution (yellow) based on the track conditions ahead.
    • Track circuits are electrical circuits installed on tracks to detect the presence of trains or vehicles. They help determine whether a particular section of track is clear or occupied, ensuring safe train movements.
    • Point switches are movable sections of the track that allow trains to change tracks. They are operated using switches and guide the wheels towards the desired direction. Point machines play a vital role in locking the point switches to ensure safe train operations.
  • The EI system enhances safety and efficiency in railway operations by preventing collisions and regulating train movements based on track conditions.

Functioning of the Electronic Interlocking (EI) System:

  • The EI system determines when a train can proceed based on two factors: the track direction and the availability of the alternate track.
  • It first checks whether the train needs to continue on the current track or switch to a different one.
  • The system then guides the train to an available track at a junction, ensuring that another train cannot enter the same section of track simultaneously through special circuits.
  • All activities within the signalling system are recorded in a microprocessor-based data logger, similar to the black box of an aircraft. This data logger can store and process signal data to generate reports.
Track Occupancy Sensing:
  • Various track-occupancy sensing devices, such as axle counters, are installed on the tracks to sense whether a track is occupied.
  • These sensors detect the passage of wheels on the rails and count the number of sets of wheels or axles that have passed over them.
  • By monitoring the number of axles passing through, the system determines whether the entire train has passed through a particular section of track.
Safety of the System:
  • The EI system is designed to be fail-safe, meaning that if any of the three components (signals, points, and track occupancy sensors) does not correspond to the overall “safe” logic fed into the computer, the system will work to stop the oncoming train.
  • In case of a failure, all signals will turn red, and train operations will come to a halt, ensuring safety.
Status of Implementation:
  • As of 2022, approximately 2,888 stations in India were equipped with an electronic interlocking system, covering about 45.5% of the Indian Railways network.
  • The implementation of EI systems aims to enhance safety and efficiency in train operations throughout the railway network.

-Source: Indian Express

July 2024