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Central Railway’s Mumbai Division Implements a modified version Advanced Auxiliary Warning System (AAWS) for Enhanced Safety and Efficiency in EMU Suburban rake cabs in place of earlier Auxiliary Warning System(AWS)

Central Railway’s Mumbai Division Implements a modified version Advanced Auxiliary Warning System (AAWS) for Enhanced Safety and Efficiency in EMU Suburban rake cabs in place of earlier Auxiliary Warning System(AWS)

Central Railway's Mumbai Division has successfully implemented the Advanced Auxiliary Warning System (AAWS) in EMU Suburban rake cabs, a cutting-edge technology designed to enhance safety measures for commuters. It has modified earlier version of Auxiliary warning system (AWS) of EMU rake cabs.

AWS is a safety mechanism installed o­n tracks and in EMU Rake cabs which monitors speed of EMU rakes according to aspects of signals and applies emergency brakes in case violation of aspects of signals accordingly. Thus ensuring safety.

AAWS, a state-of-the-art signaling system, continuously tracks the position of the driving cab in automatic signaling system of Mumbai division, ensuring precise control and monitoring of train movements.

Key features of the AAWS include:

1. Resonance-Coupled Oscillating Circuits: AAWS operates o­n the principle of resonance-coupled oscillating circuits, ensuring accurate positioning and control.

2. Dual Components: The system is comprised of two essential parts:

- Track equipment installed o­n the railway tracks

- Driving cab equipment integrated into the EMU rake

3. Control Mechanisms:

- Green/Double Yellow Signal: Speed restricted to 80 KMPH (Harbor Line) and 100/105 KMPH (Central Line).

- Yellow Signal: Speed limit set at 77.5 KMPH, with a requirement to reduce speed to 38 KMPH within 290 meters.

- Permissive Red Signal/Signal Failure Bypass: Maximum speed limited to 15 KMPH.

- Reverse Movement: Emergency brakes applied to ensure safety.

4. Speed Limit Enforcement: If speed limits are exceeded, the system enforces the following actions:

- Speed ≥ Speed Limit + 1 KMPH: Audible warning

- Speed ≥ Speed Limit + 5 KMPH: Service brakes applied

- Speed ≥ Speed Limit + 10 KMPH: Emergency brakes activated, with automatic release upon speed reduction.

5. Malfunction Reporting: AAWS reports malfunctioning data to a centralized location for swift identification of faults, ensuring rapid rectification.

6. SPAD Counter: An additional SPAD (Signal Passed at Danger) counter is included in the Indication Panel near the Motorman Desk, providing an extra layer of safety.

The progress of the AAWS implementation in Mumbai Division’s EMU rakes:

- Total Holding: 314 EMU cabs of 157 EMU rakes

- Rakes Fitted with AAWS: 226 EMU cabs of 113 rakes

- Pending: 88 EMU cabs of 44 EMU rakes (Expected Completion Date: February 2024)

A comparative analysis between AAWS (Medha made) and AWS (Siemens made) showcases the advantages of AAWS:



AAWS (Medha made)

AWS (Siemens made)


Data logging facility

Available; o­nline event monitoring for real-time system monitoring

Not available


Hardware complexity

Minimal; Utilizes o­nly 4 electronics PCB cards

More complex; Utilizes 13 electronic PCB cards


Wiring complexity

Reduced; End-to-end cables provided for each equipment

Higher; All connections routed through o­ne terminal block



More reliable; Fewer electronic PCB cards and simplified wiring

Less reliable; More electronic PCB cards and complex wiring



Low maintenance; Lower probability of failure

High maintenance requirements


Rectification of defects

Swift rectification aided by logged failure events

Longer rectification process; No logged failure events

The introduction of AAWS demonstrates Central Railway's unwavering commitment to passenger safety and operational efficiency. Central Railway looks forward to further advancements in railway technology for the benefit of our valued commuters.

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Date: September 10, 2023

PR No. 2023/09/20

This press release is issued by the Public Relations Department, HQ, Central Railway, Mumbai.

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