https://irse.signalpost.org/ Fri, 19 Jun 2026 11:28:10 +0000 MyBB https://irse.signalpost.org/showthread.php?tid=2268 Fri, 23 Feb 2018 07:07:47 +0000 shekar413]]> https://irse.signalpost.org/showthread.php?tid=2268
Could anyone explain and share documents regarding the following,

1. What is the importance of ARAFOAL and How it is applied at Level crossings?

2. What are Treadle types and Explanation about QRR and QNR relays?

3. HR front and back contacts are used in TPWS circuit for Relay operated signalling approach. What is the significance of those contacts?


Thank you,

Regards,
shekar]]>
Could anyone explain and share documents regarding the following,

1. What is the importance of ARAFOAL and How it is applied at Level crossings?

2. What are Treadle types and Explanation about QRR and QNR relays?

3. HR front and back contacts are used in TPWS circuit for Relay operated signalling approach. What is the significance of those contacts?


Thank you,

Regards,
shekar]]> https://irse.signalpost.org/showthread.php?tid=2241 Fri, 08 Dec 2017 07:23:56 +0000 Arup Bandyopadhyay]]> https://irse.signalpost.org/showthread.php?tid=2241 https://irse.signalpost.org/showthread.php?tid=1791 Wed, 06 Aug 2014 06:14:58 +0000 jenni.joseph9]]> https://irse.signalpost.org/showthread.php?tid=1791
I have a query related to placement of replacement joint for Ground Position light(GPL) in the scheme plan(Not for Module 2, Signalling the layout).

If it is placed less than 5.5m from the GPL, is it required to have last wheel replacement facility or some form of facility to delay the replacement of signal.

I have seen a case where the replacement joint is placed less than 5meters from the signal(GPL), but there was no delayed replacement for that signal.

Can someone clear this query.

Many Thanks in advance.

P.S. Network rail standards says that the replacement joint should be around 5.5m to 20m from the signal(Main) but not clearly mentioned about the GPL.]]>
I have a query related to placement of replacement joint for Ground Position light(GPL) in the scheme plan(Not for Module 2, Signalling the layout).

If it is placed less than 5.5m from the GPL, is it required to have last wheel replacement facility or some form of facility to delay the replacement of signal.

I have seen a case where the replacement joint is placed less than 5meters from the signal(GPL), but there was no delayed replacement for that signal.

Can someone clear this query.

Many Thanks in advance.

P.S. Network rail standards says that the replacement joint should be around 5.5m to 20m from the signal(Main) but not clearly mentioned about the GPL.]]> https://irse.signalpost.org/showthread.php?tid=1733 Tue, 27 May 2014 06:26:22 +0000 greatnessjason]]> https://irse.signalpost.org/showthread.php?tid=1733 In RGS GK/0202 pg 15, there is a mention of "back to back" locking. What is the history behind such type of locking and what purpose does it serve in terms of the interlocking controls?]]> In RGS GK/0202 pg 15, there is a mention of "back to back" locking. What is the history behind such type of locking and what purpose does it serve in terms of the interlocking controls?]]> https://irse.signalpost.org/showthread.php?tid=1675 Thu, 06 Mar 2014 17:57:57 +0000 asrisaku]]> https://irse.signalpost.org/showthread.php?tid=1675
Could u please help explain the function of the point machines for internal lock and external lock?

It would be really good to see how it is different in a picture.

Thanks
Arnut]]>
Could u please help explain the function of the point machines for internal lock and external lock?

It would be really good to see how it is different in a picture.

Thanks
Arnut]]> https://irse.signalpost.org/showthread.php?tid=1497 Sun, 29 Sep 2013 17:44:47 +0000 sadiqameen]]> https://irse.signalpost.org/showthread.php?tid=1497
Can you please give an insight on this statement "Controls on opposing routes are also sometimes released by the occupation, after time, of track sections" it is little hard for me to understand this statement.]]>
Can you please give an insight on this statement "Controls on opposing routes are also sometimes released by the occupation, after time, of track sections" it is little hard for me to understand this statement.]]> https://irse.signalpost.org/showthread.php?tid=1469 Wed, 28 Aug 2013 18:11:07 +0000 kannati]]> https://irse.signalpost.org/showthread.php?tid=1469
Can anyone give more guidance or material of Westpac Interlocking. I know this is GRI system for the control and interlocking of railway signalling functions. And also know that the relays are come with sets or units associated with specific signalling functions.

I would like to more details of this Interlocking working and interface with site.( I have seen this on networkrail standard 11201_B10 but I cant get more details of working and operation)

Thanks,

Kannati]]>
Can anyone give more guidance or material of Westpac Interlocking. I know this is GRI system for the control and interlocking of railway signalling functions. And also know that the relays are come with sets or units associated with specific signalling functions.

I would like to more details of this Interlocking working and interface with site.( I have seen this on networkrail standard 11201_B10 but I cant get more details of working and operation)

Thanks,

Kannati]]> https://irse.signalpost.org/showthread.php?tid=1366 Tue, 11 Dec 2012 08:12:43 +0000 savitha kandasamy]]> https://irse.signalpost.org/showthread.php?tid=1366 In GK/RT0044 , sec 4.1.2 has the following wordings.

"At each location where facilities are provided to signal trains onto Occupied Lines, the Infrastructure Controller shall specify and document the particular purposes for which those facilities are permitted to be used, and shall ensure that they are not used for any other purpose."

In this i am not able to understand about the facilities & what it is referring for. Is it referring to the signalling equipments?. Also why the facilities are not used for other purposes?. Kindly clarify.]]> In GK/RT0044 , sec 4.1.2 has the following wordings.

"At each location where facilities are provided to signal trains onto Occupied Lines, the Infrastructure Controller shall specify and document the particular purposes for which those facilities are permitted to be used, and shall ensure that they are not used for any other purpose."

In this i am not able to understand about the facilities & what it is referring for. Is it referring to the signalling equipments?. Also why the facilities are not used for other purposes?. Kindly clarify.]]> https://irse.signalpost.org/showthread.php?tid=1111 Fri, 26 Oct 2012 05:36:40 +0000 arpan_singhania]]> https://irse.signalpost.org/showthread.php?tid=1111 https://irse.signalpost.org/showthread.php?tid=1107 Wed, 24 Oct 2012 19:26:52 +0000 PJW]]> https://irse.signalpost.org/showthread.php?tid=1107 [I think because the software takes an objection to the "forward slash" character (unless it is separated by other letters by a space!) in the same way as it disallows the "percentage sign"]

Does anybody have any idea of the operation of TRTS CD RA plungers
and Indicators.
I am more concerned of the operating sequence, like which plunger is
operated first and the indication that appears first.

Any response is most appreciated.

TRTS= Train ready To Start. Operated by platform despatch staff (or when leaving depots / sidings by the shunter or driver).
Provided the relevant platform track(s) occupied causes an indication (generally blue flashing light) to illuminate on panel / VDU so that signaller's attention is drawn to it and knows that if they set the route that the train ought to be ready to leave (i.e. train crew on board, no expected station delays with disabled / luggage / large groups etc)- hence provoked to set route and commit the station throat pointwork for that train movement. Also used as an input to Automatic Route Setting. Indication continues until signal aspect actually clears.

CD= Closed Door. Indicates as auxiliary indication on signal itself and may be at several places along length of platform. Tells driver that station duties complete and should close the doors on power worked sliding door rolling stock. Driver learns that all doors have closed by the in cab door interlock light illuminating. Officially does not need to be interlocked with the signalling, but generally provided as part of the signalling system and then would generally prove that the signal is showing a proceed aspect (including PL) before it can illuminate.

RA-= Right Away. This is operated by platform staff to authorise train to leave- confirming that no one on the platform has clothing caught in the doors, no one fell down gap between train and platform on curved track etc. Replaces the traditional waving of green flag and blowing whistle by guard.
Generally provided in the same housing as the CDs, so the CD is extinguished once the RA lights. To avoid the hazard of driver failing to check signal aspect once provoked to depart by platform staff, the RA is interlocked- it can only illuminate if signal is off.


The TRTS is not safety critical and therefore generally plunger operated.

The CD is arguably, and the RA definitely is, safety critical so they are operated by key-switch and there is sequential proving to ensure that the switch is operated and released, so there needs to be a positive action to cause the indicators to illuminate.]]> [I think because the software takes an objection to the "forward slash" character (unless it is separated by other letters by a space!) in the same way as it disallows the "percentage sign"]

Does anybody have any idea of the operation of TRTS CD RA plungers
and Indicators.
I am more concerned of the operating sequence, like which plunger is
operated first and the indication that appears first.

Any response is most appreciated.

TRTS= Train ready To Start. Operated by platform despatch staff (or when leaving depots / sidings by the shunter or driver).
Provided the relevant platform track(s) occupied causes an indication (generally blue flashing light) to illuminate on panel / VDU so that signaller's attention is drawn to it and knows that if they set the route that the train ought to be ready to leave (i.e. train crew on board, no expected station delays with disabled / luggage / large groups etc)- hence provoked to set route and commit the station throat pointwork for that train movement. Also used as an input to Automatic Route Setting. Indication continues until signal aspect actually clears.

CD= Closed Door. Indicates as auxiliary indication on signal itself and may be at several places along length of platform. Tells driver that station duties complete and should close the doors on power worked sliding door rolling stock. Driver learns that all doors have closed by the in cab door interlock light illuminating. Officially does not need to be interlocked with the signalling, but generally provided as part of the signalling system and then would generally prove that the signal is showing a proceed aspect (including PL) before it can illuminate.

RA-= Right Away. This is operated by platform staff to authorise train to leave- confirming that no one on the platform has clothing caught in the doors, no one fell down gap between train and platform on curved track etc. Replaces the traditional waving of green flag and blowing whistle by guard.
Generally provided in the same housing as the CDs, so the CD is extinguished once the RA lights. To avoid the hazard of driver failing to check signal aspect once provoked to depart by platform staff, the RA is interlocked- it can only illuminate if signal is off.


The TRTS is not safety critical and therefore generally plunger operated.

The CD is arguably, and the RA definitely is, safety critical so they are operated by key-switch and there is sequential proving to ensure that the switch is operated and released, so there needs to be a positive action to cause the indicators to illuminate.]]> https://irse.signalpost.org/showthread.php?tid=1054 Tue, 24 Jul 2012 22:10:54 +0000 PJW]]> https://irse.signalpost.org/showthread.php?tid=1054 The question is: In the UK Railway Group Standards, referring to TORR, it implies that for TORR to be effective (i.e. to work), the signal in question must have been OFF when the train passed the signal.
i.e. if the operator pulls the button in front of a train which then runs past the signal at red, TORR is not effective. Similarly if the operator sets a route and the signal doesn't clear and the train is called past the signal, then TORR isn't effective.

Can you confirm the rationale for requiring the signal to be off when the train passed the signal?

My response was as given below; I'd be interested to see if others disagree / can add anything more to it:

I don't think you'll find this rationale written down anywhere; the place I would look would be the relevant chapter of SSI data prep in the SSI8xxx series, but not over hopeful.......Hence this is my own take-

Basically the feature is implemented by requiring the signal stick GSR down (or signal stick xs in SSI data).
This "circuit" consists of parallel paths:
a) berth track clear,
b) first tracks clear,
c) signal RGPR (proving signal at red- the "pumping stick" feature originally provided to allow route to be over-set with train still on this track)

Hence if a train passes signal in the normal manner, the circuit loses a, then b just before gaining c so the stick path is broken. It gives directionality and a pretty good proof that train has actually passed the signal whilst it was displaying proceed (as you detected within the wording of the standard).

As per the actual question you asked- the rationale. I don't absolutely know for sure but my assertion is this.
TORR introduced primarily to support Automatic Route Setting (as it is obvious ARS without TORR wouldn't actually give much benefit!)

There are always hazards relating to absolute reliance upon track circuit train detection- there can be "bobs" when a train briefly disappears due to poor train shunt; also there are many things that can cause a track to appear to be occupied when it is really clear.
A signaller is deemed to be vigilant and to have some intelligence and therefore will stop and think just prior to cancelling a route, doing some form of "double check" that
1. there is no train is approaching the signal and therefore a driver to see an aspect reversion, in addition to
2. satisfying themselves that either the route has been used or that it is appropriate to change the priorities at the junction which had been committed but not yet used for a train.
Whilst a route remains set it holds the locking for any points, level crossing, opposing moves and hence is the last line of defence. Prior to TORR, the signalling already had "approach locking"; therefore the need to provide something additional, using at least one different train detection device, to implement what would otherwise be done by signaller's fingers following appropriate data processing by their brain.

TORR was first implemented on Southern Region (certainly Wimbledon for Waterloo in "Yellow Book free wire" but may also have been earlier such as London Bridge as I think it was in Westpac 4 but my memory is hazy on this); on SR one tends not to be able to achieve a drop shunt of 0.5 ohm but have to accept 0.3 ohm because of the number of impedance bonds on ac vane tracks. In that environment the occasional brief track flick isn't really that unusual. particularly as traction fault effects can giving traction current imbalance in the running rails.

It would not be inconceivable that a single fault (power supply interruption, dodgy insulated rail joint between two track circuits) would cause both to become occupied and then become clear again with one of them being slower to pick than the other- hence they would appear to give a sequence looking as if train had passed. There is a "Power Off" relay that ought to inhibit this in circumstances in which the interlocking itself has lost power, but this wouldn't protect in all circumstances of local power interruption and certainly not for a dodgy IRJ. We wouldn't want to cancel and free the A/L of a route in such circumstances.

Another factor is that ARS is always looking to set routes if due to be set- it is a computer looking for "opportunity" and should it ever see all the point availability conditions simultaneously satisfied it will "get in there" and launch its route request. Therefore the risks associated with lack of perfection of the interlocking / train detection are vastly increased- if a track bobbed and freed all the route locking before becoming properly occupied again, a signaller would not likely to be quick enough to request the route in the "time window" (assuming that the track deadlocked one of the relevant points) and also should anyway think "where the #@*% has that other train gone".

ARS on the other hand would just say "great, the conditions I have been monitoring are all now satisfied so I can do what I have been waiting to do and thus avoid unnecessary delay to my train. It only considers on a train by-train basis when it wants to set a route; it has no real comprehension of the big picture, just evaluating priorities to get a string of green aspects ahead of trains.

The mindset is that ARS should take the routine workload off the signaller, but leave them in control. Hence whereas a signaller can key points or set routes themselves and thus constrain ARS to follow their lead and it will work with them, should a signaller cancel any route prior to passage of train, the ARS is designed to switch off its relevant sub-area on the basis that the signaller did so for a reason and if ARS remained active then it would be competing for control and could do something contradictory.

If a signal is replaced to danger when a train is close to it and then the train passes it as it is unable to stop, the situation is clearly abnormal; hence the rationale: leave the signaller fully in control as they are probably aware of the current scenario in a way that cannot be envisaged by the signalling designer generically.

If a route has been set for a train which has not cleared (perhaps waiting for approach release or the lamp proving of a route indicator) and a train passes it invalidly (going too fast, driver anticipating clearance, sees a route indicator but failure of lamp proving keeps signal at red- all are SPADs for which the driver is responsible) then again wouldn't want to change anything and free up locking. There will need to be an investigation and (certainly in the days of RRI without data monitoring kit) hence very undesirable to destroy evidence of the state at the time of the incident- if the route TORRs there may subsequently be doubt it was ever even set.

So in summary the rational seems to go like this:
1. Increased area of control requires workload to be taken from signaller and can't expect them to be so vigilant as when responsible for a small area and few trains simultaneously
2. ARS increases the likelihood of a weakness in interlocking being exploited by a computer without any common sense
3. More reliance has to be placed on integrity of route cancellation / normalisation- do in the interlocking not the control system
4. The GSRs already exist and have plenty of spare contacts; hence including this level of proof costs almost nothing and provides the benefit of a good confidence that the railway is in "normal operating scenario" conditions; hence it is a "no-brainer" to include within the TORR function.

SSI program and data very much followed the RRI implementation wherever it could (some things like route locking , comprehensive Approach Locking are considerably different but there is a reason for this- the default position was to keep as similar as possible, no doubt for ease of acceptance by a conservative industry.

Perhaps over the years we have become slightly more comfortable- often nowadays the TORR is performed in the SIL2 control system when a pre-exsisting RRI is transferred from a panel signalbox to a new large VDU based control centre. We still implement the same logic of requiring the "stick unset" though.

Any more ideas to reinforce / refute ? ]]> The question is: In the UK Railway Group Standards, referring to TORR, it implies that for TORR to be effective (i.e. to work), the signal in question must have been OFF when the train passed the signal.
i.e. if the operator pulls the button in front of a train which then runs past the signal at red, TORR is not effective. Similarly if the operator sets a route and the signal doesn't clear and the train is called past the signal, then TORR isn't effective.

Can you confirm the rationale for requiring the signal to be off when the train passed the signal?

My response was as given below; I'd be interested to see if others disagree / can add anything more to it:

I don't think you'll find this rationale written down anywhere; the place I would look would be the relevant chapter of SSI data prep in the SSI8xxx series, but not over hopeful.......Hence this is my own take-

Basically the feature is implemented by requiring the signal stick GSR down (or signal stick xs in SSI data).
This "circuit" consists of parallel paths:
a) berth track clear,
b) first tracks clear,
c) signal RGPR (proving signal at red- the "pumping stick" feature originally provided to allow route to be over-set with train still on this track)

Hence if a train passes signal in the normal manner, the circuit loses a, then b just before gaining c so the stick path is broken. It gives directionality and a pretty good proof that train has actually passed the signal whilst it was displaying proceed (as you detected within the wording of the standard).

As per the actual question you asked- the rationale. I don't absolutely know for sure but my assertion is this.
TORR introduced primarily to support Automatic Route Setting (as it is obvious ARS without TORR wouldn't actually give much benefit!)

There are always hazards relating to absolute reliance upon track circuit train detection- there can be "bobs" when a train briefly disappears due to poor train shunt; also there are many things that can cause a track to appear to be occupied when it is really clear.
A signaller is deemed to be vigilant and to have some intelligence and therefore will stop and think just prior to cancelling a route, doing some form of "double check" that
1. there is no train is approaching the signal and therefore a driver to see an aspect reversion, in addition to
2. satisfying themselves that either the route has been used or that it is appropriate to change the priorities at the junction which had been committed but not yet used for a train.
Whilst a route remains set it holds the locking for any points, level crossing, opposing moves and hence is the last line of defence. Prior to TORR, the signalling already had "approach locking"; therefore the need to provide something additional, using at least one different train detection device, to implement what would otherwise be done by signaller's fingers following appropriate data processing by their brain.

TORR was first implemented on Southern Region (certainly Wimbledon for Waterloo in "Yellow Book free wire" but may also have been earlier such as London Bridge as I think it was in Westpac 4 but my memory is hazy on this); on SR one tends not to be able to achieve a drop shunt of 0.5 ohm but have to accept 0.3 ohm because of the number of impedance bonds on ac vane tracks. In that environment the occasional brief track flick isn't really that unusual. particularly as traction fault effects can giving traction current imbalance in the running rails.

It would not be inconceivable that a single fault (power supply interruption, dodgy insulated rail joint between two track circuits) would cause both to become occupied and then become clear again with one of them being slower to pick than the other- hence they would appear to give a sequence looking as if train had passed. There is a "Power Off" relay that ought to inhibit this in circumstances in which the interlocking itself has lost power, but this wouldn't protect in all circumstances of local power interruption and certainly not for a dodgy IRJ. We wouldn't want to cancel and free the A/L of a route in such circumstances.

Another factor is that ARS is always looking to set routes if due to be set- it is a computer looking for "opportunity" and should it ever see all the point availability conditions simultaneously satisfied it will "get in there" and launch its route request. Therefore the risks associated with lack of perfection of the interlocking / train detection are vastly increased- if a track bobbed and freed all the route locking before becoming properly occupied again, a signaller would not likely to be quick enough to request the route in the "time window" (assuming that the track deadlocked one of the relevant points) and also should anyway think "where the #@*% has that other train gone".

ARS on the other hand would just say "great, the conditions I have been monitoring are all now satisfied so I can do what I have been waiting to do and thus avoid unnecessary delay to my train. It only considers on a train by-train basis when it wants to set a route; it has no real comprehension of the big picture, just evaluating priorities to get a string of green aspects ahead of trains.

The mindset is that ARS should take the routine workload off the signaller, but leave them in control. Hence whereas a signaller can key points or set routes themselves and thus constrain ARS to follow their lead and it will work with them, should a signaller cancel any route prior to passage of train, the ARS is designed to switch off its relevant sub-area on the basis that the signaller did so for a reason and if ARS remained active then it would be competing for control and could do something contradictory.

If a signal is replaced to danger when a train is close to it and then the train passes it as it is unable to stop, the situation is clearly abnormal; hence the rationale: leave the signaller fully in control as they are probably aware of the current scenario in a way that cannot be envisaged by the signalling designer generically.

If a route has been set for a train which has not cleared (perhaps waiting for approach release or the lamp proving of a route indicator) and a train passes it invalidly (going too fast, driver anticipating clearance, sees a route indicator but failure of lamp proving keeps signal at red- all are SPADs for which the driver is responsible) then again wouldn't want to change anything and free up locking. There will need to be an investigation and (certainly in the days of RRI without data monitoring kit) hence very undesirable to destroy evidence of the state at the time of the incident- if the route TORRs there may subsequently be doubt it was ever even set.

So in summary the rational seems to go like this:
1. Increased area of control requires workload to be taken from signaller and can't expect them to be so vigilant as when responsible for a small area and few trains simultaneously
2. ARS increases the likelihood of a weakness in interlocking being exploited by a computer without any common sense
3. More reliance has to be placed on integrity of route cancellation / normalisation- do in the interlocking not the control system
4. The GSRs already exist and have plenty of spare contacts; hence including this level of proof costs almost nothing and provides the benefit of a good confidence that the railway is in "normal operating scenario" conditions; hence it is a "no-brainer" to include within the TORR function.

SSI program and data very much followed the RRI implementation wherever it could (some things like route locking , comprehensive Approach Locking are considerably different but there is a reason for this- the default position was to keep as similar as possible, no doubt for ease of acceptance by a conservative industry.

Perhaps over the years we have become slightly more comfortable- often nowadays the TORR is performed in the SIL2 control system when a pre-exsisting RRI is transferred from a panel signalbox to a new large VDU based control centre. We still implement the same logic of requiring the "stick unset" though.

Any more ideas to reinforce / refute ? ]]> https://irse.signalpost.org/showthread.php?tid=1002 Thu, 29 Mar 2012 10:39:26 +0000 NJK]]> https://irse.signalpost.org/showthread.php?tid=1002
The below statement I read in one training material.

It is an unwritten assumption that an aspect may at any time "step up" to a less restrictive aspect due to the clearing of signals beyond, but in normal circumstances will not step down to a less restrictive aspect.

I am not understand the text which is available in bold.

Please clarify.]]>
The below statement I read in one training material.

It is an unwritten assumption that an aspect may at any time "step up" to a less restrictive aspect due to the clearing of signals beyond, but in normal circumstances will not step down to a less restrictive aspect.

I am not understand the text which is available in bold.

Please clarify.]]> https://irse.signalpost.org/showthread.php?tid=931 Tue, 18 Oct 2011 03:36:12 +0000 onestrangeday]]> https://irse.signalpost.org/showthread.php?tid=931
Recently, I came across a signalling terminology "stick lock", can anyone define what does it mean ?

and in what situation would the "stick lock" be applied in the signalling design ?



thanks


]]>
Recently, I came across a signalling terminology "stick lock", can anyone define what does it mean ?

and in what situation would the "stick lock" be applied in the signalling design ?



thanks


]]> https://irse.signalpost.org/showthread.php?tid=925 Thu, 29 Sep 2011 08:22:54 +0000 ch86]]> https://irse.signalpost.org/showthread.php?tid=925
Cheers]]>
Cheers]]> https://irse.signalpost.org/showthread.php?tid=879 Fri, 19 Aug 2011 07:13:32 +0000 fil]]> https://irse.signalpost.org/showthread.php?tid=879 Am I right in thinking that permissive working is not an acceptable means of working for anything other than coupling trains?
If so, how do we control platform sharing? Signals mid platform seems the obvious solution but how would one get the required overlap?

Thanks
]]> Am I right in thinking that permissive working is not an acceptable means of working for anything other than coupling trains?
If so, how do we control platform sharing? Signals mid platform seems the obvious solution but how would one get the required overlap?

Thanks
]]>