TPWS or ACD ; the debate .

Please read the following News Items/ Criticism regarding non/ slow adoption of ACD and apparent preference for  other established systems like TPWS (Train Protection Warning system) or ETCS/ERTMS on Indian Railways :

Rail anti-collision tech: Does the foreign TPWS trump the home-grown ACD?
April 26, 2010 06:14 PM

The Indian Railways has once again chosen an expensive foreign technology (TPWS) over India’s own patented ACD system

The Indian Railways recently decided to adopt the European technology Train Protection Warning System (TPWS) on busy rail routes to avoid collisions. However, the government has once again ignored the indigenous & cost-effective anti-collision device (ACD) system developed by the Konkan Railway and has instead opted for an expensive foreign technology. 

According to industry experts, TPWS is not only expensive, but also less efficient compared to the ACD system. Rajaram Bojji, inventor of the ACD technology and former managing director, Konkan Railway, has also written to the railway minister on this issue.

In his letter addressed to the minister, he has stated, “You have chosen to approve more expensive systems which do not provide the protection against collisions as widely as ACD can provide. You are ill-advised.”

Commenting on the features of the TPWS, a senior railway ministry official was quoted in a news report as stating, “If the train jumps the red signal, then brakes will be applied automatically under the TPWS system. A majority of the recent accidents took place due to trains jumping red signals in foggy conditions.”

The TPWS is estimated to cost Rs70 lakh per km, and will be implemented over an 828-km rail stretch. The total cost for installing the TPWS would be about Rs579.60 crore. On the other hand, the ACD will provide a more efficient and cheaper overall protection against collisions.

ACD, which is a no-signal equipment, has superior wide-area safety-enhancing capability, while costing much less individually.

The signal department of the Indian Railways demands a Safety Integrity Level (SIL) certification for ACDs. However, Mr Bojji stated, “ACD, actually not being signal equipment, but only an additional layer, does not need SIL certification, this was confirmed by TUV Germany too in their report for assessing the ACD.”


Railways are planned to adopt Train Protection and Warning System (TPWS)

Sep 16th, 2009 by affroze

It has been planned to adopt Train Protection and Warning System (TPWS), a variant of Auxiliary Warning System (AWS), to further enhance safety levels in train operations by preventing cases of ‘Signal Passed at Danger’ in 280 Track kilometres of ‘A’ route on Southern and North Central Railway, on trial basis.

Functionality wise there is no difference between the two systems, which are basically meant to prevent driver passing signal at danger. However, both the systems use different technologies to achieve the intended functionality.

The conventional AWA system uses track magnet, which are basically made of Copper, as track device making it prone to thefts. Information about signal aspect, in AWS, is transmitted from track device to cab equipment through electro magnetic induction.

TPWS use Euro Balise as a track device, which is an electronic device with very less copper inside and it uses radio transmission for sending information to cab equipment.

TPWS is basically meant to prevent driver from passing a signal at danger thereby preventing accident thereof. The system does not have any functionality, which can curtail outside interference of rail installation, such as track and signal equipment.

The IRSSE opinion on the Technological Choices …


It is surprising that the very basic flaw (or the  this author perceives as an Engineer) is that ACD is a  Technology TOTALLY based on GPS (or Global Positioning system) which is  based on a US Govt controlled  satellite system. Indian Railways never opted for satellite based systems for anything having safety or operational ramifications. GPS access can be suddenly denied by US Govt in a Hostile situation or any Technical failure or a shift to different Technology by them  for their Strategic / Business reasons can put entire Indian Rail Network safety in a great  jeopardy.

Also the chance of  neighboring  enemy  Powers trying to jam GPS radio signals in a war like situation. More over it is Essential that any systems that controls train movement shall be closely linked with the existing Rail Signalling Systems which have gone through rigid safety standards (such as SIL reqmts).

Obviously Railway safety is not about Gadgetry but a serious professional strategic  realm of Public Interest..



About Railway Signalling ; for common man

Railway Signalling

Signalling is one of the most important parts of the many components  which make up a railway system.  Train movement safety depends on it and the control and efficient management of trains depends on them.  Over the years many signalling and train control systems have been evolved. The journey started with very simple systems such as simple coloured flags and semaphore arms to that today a highly

technical and complex  electrical and electronic systems. Here is an attempt to explain, in simple terms, how railway signalling really works.

Lower Quadrant :

In IR’s lower quadrant system (Two-aspect Lower Quadrant) the semaphore arm can only be in two positions. The horizontal ON position shows the most restrictive indication (requiring the train to stop or slow down or proceed with caution depending on the kind of signal), and a lowered position (OFF)  where the semaphore arm is at about 60 degrees or more from the horizontal shows the clear or proceed indication allowing a train to go past the signal.

Fig-1  Semaphore Signals that stoop (lower quadrant)

Upper Quadrant

Properly, Multiple Aspect Upper Quadrant, in this system there are three signal positions. The 12 o’clock position is clear or proceed, which gives a train permission to go past the signal without stopping. An intermediate position (at 45 degrees to the vertical) is the attention or caution indication; the meaning depends on the kind of signal. The horizontal position, where the semaphore arm is horizontal, the onposition, is the most restrictive indication of the signal; it may require the train to stop, or to proceed with caution, etc., depending on the kind of signal.

Fig-2  Semaphore Signals that raise (upper quadrant)

Nowadays IR has converted what are known as Color Light Signals (CLS) with Multiple aspects where the color of Light indicates meaning to Drivers ( Now called Loco Pilots).

Fig-3: Multiple aspect Color Light Signals

  • Two-aspect colour-light signalling – In this, each signal has two lamps (one above the other). The higher of the two is a green lamp, and the lower one is a red lamp. The green lamp when lit indicatesclear (the proceed indication), and when the red lamp is lit, the signal is said to be in the on position, displaying its most restrictive indication.
  • Three-aspect colour-light signalling – In this, each signal has three lamps arranged vertically. The top one is green, the middle one yellow, and the bottom one is red. The red and green lamps indicate indications as in the 2-aspect system, and the yellow lamp shows the caution indication.
  • Four-aspect colour-light signalling – This is also known just as Multiple-aspect colour-light signalling (MACL or MACLS) and adds another yellow lamp to the 3-aspect system. The additional yellow lamp can be placed above the green lamp in a 4-lamp signal. In this case, the lower yellow lamp alone is lit to show the caution indication, and both yellow lamps are lit to show the attention indication. Alternatively, a different kind of 3-lamp signal may be used (e.g., for distant signals), where the top and bottom lamps are yellow and the middle one is green. Again, both yellow lamps light up to indicate the attentionindication.

Meanings of Aspects :

Danger Caution Attention Proceed

FIg-4 : Aspects (Appearance to Driver) and Meanings

  • Stop This requires a train to stop dead and not pass the signal except under special instructions or emergency procedures. (Stop signals may be passed after halting and waiting in automatic block territory – usually 1 min. during the day & 2 min. during the night.) This indication is also known as Danger.
  • Caution This allows a train to proceed past the signal with caution (at reduced speed), being prepared to stop at the next signal. It can mean that the next signal is at Danger, or that the track ahead has speed restrictions.
  • Attention This allows a train to proceed past the signal, being prepared to slow down to an appropriate speed for the next signal. It means that the next signal may be at Caution, or may guard a divergence which requires reduced speed (in which case a stop signal at the divergence will indicate the route for which points are set).
  • Proceed This allows the train to proceed past the signal without slowing down or stopping.

Why Signalling is required?

In road transportation the direction and speed of a vehicle are controlled by the driver and the different vehicles share the same way at the same time in both the directions. However in Rail transport the the driver controls only the  start / stop and speed of the train and the direction is controlled by the track components themselves. There is no steering wheel. One more  factor to be considered is that the trains are very large vehicles and hence need large distances to increase and decrease speed i.e to start and stop also. Hence they need to be separated by considerable distances while traveling behind one another.

Thus the signaling has the following basic functions :-

1.      Arranging safe reception and dispatch of trains onto required lines at  stations.

2.      Ensuring that trains are not received on occupied lines

3.      Ensuring that two trains donot enter the same part of the track between two  stations (Also called block signaling)

4.      Optimizing the utilization of track and other assettes by allowing the  dealing of maximum no of trains  at highest speeds permitted by track and train vehicles safely.

5. Ensuring that no part of the train is left over in Block section between two stations (Optional)

6.     Achieve all the above in a manner called  ” Fail safe which makes  signalling a unique field of Engineering as every component and particularly the combination shall not fail to an unsafe end result at any cost.

To achieve the above functions the follwing devices are used :

1. Track circuits : are simple electric gadgets that are filtted to tracks and detect the presence of trains over that portion of the track. They prevent allowing of signals on the same portion by fixing the signals at Danger (RED) position till such time the trains leaves that portion. Thus this gadget allows dealing of trains without colloisions.

Fig-5  Track Circuit – General

Fig 5a – The Track Circuit – Without Train (Signal can turn Green)

Fig 5b – The Track Circuit – Occupied by train  (Signal goes to Red)

Fig 6 – The Functioning of Axle Counters

Other Components :

  • Point machines ( to change points; read below about points)
  • Relay or Electronic Interlocking for correlating all field gears before clearing signals)
  • Panels with yard diagram for taking orders from Station master
  • Block Instruments for ensuring that two trains donot enter the space between two stations in an unsafe manner.
  • Lifting barriers to ensure road vehicles are not allowed during train movements
  • Signals of different types to inform driver to move or stop
  • Dataloggers to monitor correct sequences and pre warning or analyzing  unsafe outcomes
  • Automatic Signalling which works without humanintervention in busy sections esp in suburban transport
  • Advanced Train wraning and train protection systems
  • Powersupply systems to support reliable and safe working of Signalling

Signalling at Stations :-

We are aware that though there are only one or two lines between stations (called block section); at stations there are many lines onto which the trains are allowed to be received and dispatched. We have also learned that a train driver cannot steer his train in the required direction. Thus railway is called guided transportation. The track itself modifies its components dynamically to lead the train to required line (platform). An important part of the track that achieves routing of trains is a point.

Point  also called Turnout

Fig 7a: Point : also called a switch is a device on the track that Guides a train into any given  Platform or Track-line at a Rly. station, in the above picture the point is set for the line on the RHS …..
Fig 7b :  (Click to see animation) Animated demonstration of How a Point can lead train wheels in different Directions

All such points and connected line at a station is known as a yard. A typical simplified signalling diagram is indicated below:
Fig 6 : Yard Signalling sketch of  a small station  on  Double Line (Double Line Means seperate tracks between stations for UP and DOWN direction trains).

The Opportunities in General Posts ..

All IRSSE officers are in general sincere, mostly conservative (in a positive sense) and hard working like many other Rly men, but it helps to give them better opportunities to get the BEST out of them.

You are all aware that saturation has been affecting IRSSE more than any other Group-A Railway service.

Please go through the following attachments (links) and you will know that  more representation (proportionate) in General cadre posts like GM/DRM/CSO/SDGM/ADRM etc would have put the SAG promotions and carde as such in a in better stead. Apart from links I have put down a summary which many of you might be aware:

A. GMsGM FEB 10; (Feb-10)

(as on Feb-10 an indicative list to give relative position of Services)

1. Total Posts  (GM and Members ) :  30 (23+7)

2. Share of Services :

IRTS: 10       IRSME: 08          IRSE :04        IRSEE: 05

IRSSE:01 IRAS : 02           IRSS: 00        IRPS  : 00

(Sri CP Verma IRSSE,  joined as GM/CORE on 30-07-2010)

B). AGMs also for relative understanding :AGMs 26.4. (Apr-10)

1. Total Posts  : 09

2. Share of Services :

IRTS: 03       IRSME: 04    IRSE :01    IRSEE: 01

IRSSE :00      IRAS : 00       IRSS: 00    IRPS : 00

C). SDGMs : SDGMs 26.4(Apr-10)

1. Total Posts  : 09

2. Share of Services :

IRTS: 04    IRSME: 04    IRSE :04   IRSEE: 02

IRSSE:00    IRAS : 01     IRSS: 00   IRPS : 00

D). DRMs : DRMs LIST 26.4 (Apr-10)

1. Total Posts : 68

2. Share of Services :

IRTS: 15    IRSME: 17    IRSE :15   IRSEE: 10

IRSSE:04    IRAS : 04      IRSS: 02    IRPS : 01

E). ADRMs :  ADRM list 9.3.10 (Mar-10) (ADRM posts are meant for Cadre Balancing)

1. Total Posts : 68

2. Share of Services :

IRTS: 08     IRSME: 19      IRSE :10   IRSEE: 23

IRSSE:02 IRAS : 03       IRSS: 03    IRPS : 05


1. Total Posts : 195

2. Share of Services :

IRTS: 40 IRSME: 52 IRSE :34 IRSEE: 41

IRSSE:07 IRAS : 10 IRSS: 05 IRPS : 06

IRTS: 20%    IRSME: 26%   IRSE :17%    IRSEE: 21%

IRSSE:3.5%   IRAS : 5.2 %   IRSS: 2.5%   IRPS :  03%

The Pie :



IRSSE stands for …

What is IRSSE ?

IRSSE stands for Indian Railway Service of Signal Engineers , an Organized Gazetted Government service of the Government of India.

The incumbents are selected by the Union Public Services Commission, the apex gazetted recruitment body of the Goverment of India. The examination consists of CESE ; all india written test followed by interview for selected candidates. Based on the marks obtained, a choice can be made to join this service. It has been common in the past 20-25 years for toppers from EEE/ECE streams of CESE  to join this service.

This site is created by one of the mebers of this service with a view to creating public awareness about this important service responsible for safe and speedy train travel and creating user friendly Passenger information systems and public interfaces.

Brief Role :

Signal Engineers in Railway take care of Train safety in Operations, Capacity enhancement, Corporateand Operational  Telecom and IT services, creation of Electronic interfaces for Passenger information dispersal and creation of advanced Signal and Telecom (and IT) assettes as per Operational Requirements.

A Warm Welcome …

Welcome IRSSE pals and the rest of Indian Railway community. The fact is that we started a website on ( which is being inaccessible  to most users off late.  WEBS perhaps is playing spoil sport with FREE users. Inconvenience caused is regretted…

I came across wordpress blogs which have been working consistently. Why not give a try.. A serious one at that before IRSSE goes for a professional site?

Please post your comments and express unity…. so that I can go ahead