GWML Electification

[Banger Blue]

If we are talking about the signs at Reading, which are white circles with the black triangle in the middle, they aren’t classed as Signals they are simply  “rear clear” marker boards to indicate to the driver that the rear of their formation is in clear of a given point.

 

I’m not 100% sure but I think they don’t need to get permission from the PiC of the platform to move once in the platform, just the signaller. Depending on wether they stop at the marker board or carry on down to the platform signal will depend on the direction of their next move or if another unit is to attach.

 

i was going to include a link to the marker boards on the Railway Signs and Signals of GB website but it would appear the website owner has had a bit of a tantrum and thrown their teddies out the cot over the result of the General Election!! 
 

http://www.railsigns.uk/home.html

Edited December 29, 2019 by Banger Blue

[Zomboid]

It's strange that essentially the same functionality has been achieved in such different manners at Bristol and Reading though.

 

Since I've seen 3 trains stacked up on the same platform at Cardiff I would imagine that's done in a different way again.

 

And then Southampton Central has the same functionality, which is probably a 4th entirely different approach...

[Fat Controller]

1 hour ago, Banger Blue said:

If we are talking about the signs at Reading, which are white circles with the black triangle in the middle, they aren’t classed as Signals they are simply  “rear clear” marker boards to indicate to the driver that the rear of their formation is in clear of a given point.

 

I’m not 100% sure but I think they don’t need to get permission from the PiC of the platform to move once in the platform, just the signaller. Depending on wether they stop at the marker board or carry on down to the platform signal will depend on the direction of their next move or if another unit is to attach.

 

i was going to include a link to the marker boards on the Railway Signs and Signals of GB website but it would appear the website owner has had a bit of a tantrum and thrown their teddies out the cot over the result of the General Election!! 
 

http://www.railsigns.uk/home.html

Whilst there seem to be problems with the dummy/ pram Interface, this may be of some interest:

https://catalogues.rssb.co.uk/rgs/standards/RIS-0758-CCS Iss 1.1.pdf

[St. Simon]

2 hours ago, Banger Blue said:

I’m not 100% sure but I think they don’t need to get permission from the PiC of the platform to move once in the platform, just the signaller. Depending on wether they stop at the marker board or carry on down to the platform signal will depend on the direction of their next move or if another unit is to attach.

Rear Clear Markers are advisory indicators, you don’t need permission to pass them by themselves.

 

Drivers aren’t required to stop at them, it’s just at Reading they provide a better reference point rather than a car stop marker.

 

Simon

Edited December 29, 2019 by St. Simon

[St. Simon]

2 hours ago, Zomboid said:

It's strange that essentially the same functionality has been achieved in such different manners at Bristol and Reading though.

 

Since I've seen 3 trains stacked up on the same platform at Cardiff I would imagine that's done in a different way again.

 

And then Southampton Central has the same functionality, which is probably a 4th entirely different approach...

Hi,

 

The different approaches are due to different requirements by the operations department, none of them are ‘wrong’, just tailored to the particular scenarios they are designed for. Whilst they appear to achieve the same thing, they achieve subtly different objectives

 

We don’t sit in the office and pluck ideas out of thin air on a whim when we feel like it.

 

Simon

[jim.snowdon]

43 minutes ago, St. Simon said:

Hi,

 

The different approaches are due to different requirements by the operations department, none of them are ‘wrong’, just tailored to the particular scenarios they are designed for. Whilst they appear to achieve the same thing, they achieve subtly different objectives

 

We don’t sit in the office and pluck ideas out of thin air on a whim when we feel like it.

 

Simon

Which rather makes it appear that although NR is one railway it cannot do things consistently. And, no, the impression that I have of signalling design it that it is now done very much according to the stone tablets, not least so as to establish consistency.

 

Jim

[DY444]

4 hours ago, The Stationmaster said:

Ah - so replacing the St Andrews Cross which had a zero overlap with a signal which has a zero overlap has meant reducing the line speed from 25mph to 10mph.  I believe that is called 'progress'   (Incidentally it takes things back to exactly how they were when before the St Andrews Crosses replaced the 1930s colour light signals - when the speed limit was 10 mph.).  

 

Clearly the SPAD risk element in the new Temple Meads signalling will (should?) have been properly assessed in the design stage and while such techniques are not necessarily used in that process it would have been illuminating, to say the very least, to see the result of a quantitive risk assessment of the risks of using the St Andrews Crosses with a 25mph speed limit as it could have used real data over several decades to assess the 'likelihood' element of keeping that line speed.

 

The difference was that under the old arrangement if the platform was occupied beyond the St. Andrews cross (or indeed anywhere) then the east/west gantry signal only cleared with a sub aspect.  Reliance was then placed on the driver obeying the rule book and proceeding in such a way that they could stop short of any obstruction. 

 

PS.  To summarise.  Under the old system trains were obliged to run at a slow enough speed to stop short of an obstruction only when the platform was occupied and they were required to stop at the St. Andrews cross or the obstruction whichever they got to first.  Otherwise the only constraint was the 25mph limit and the need to stop at the St.Andrews cross or beyond depending on the platform number.  All trains could depart at up to 25mph.  Under the new system everything is limited to 10mph irrespective of the occupancy of the platform and irrespective of whether it is arriving or departing.  

Edited December 29, 2019 by DY444

[caradoc]

Presumably the St Andrews Crosses at Temple Meads were installed due to being cheaper and easier to provide than mid-platform signals. Would it not be simpler to remove them and arrange the approach signals to clear to a main aspect if the platform is clear throughout or a subsidiary aspect if it is occupied ?

[jim.snowdon]

2 hours ago, caradoc said:

Presumably the St Andrews Crosses at Temple Meads were installed due to being cheaper and easier to provide than mid-platform signals. Would it not be simpler to remove them and arrange the approach signals to clear to a main aspect if the platform is clear throughout or a subsidiary aspect if it is occupied ?

I can imagine that being the case if there the signalling design had reached an advanced stage without any mid-platform signals, simply because change is expensive, particularly with the modern computer based interlockings. But, the use of mid-platform signals would have been an entirely logical feature - simple, straightforward and conforming to established practice.

The issue of zero (or more accurately significantly reduced) overlap is only an issue when the other half of the platform is already occupied by a train, and there are straightforward soluitions to dealing with negligible overlaps - London Underground had more than a few round parts of the Metropolitan/Circle Line.

I am, though, left with the impression that the arrangement at Bristol was a "how do we get ourselves out of a problem at minimum cost" solution.

 

Jim

[royaloak]

I will leave it up to others.

Edited December 30, 2019 by royaloak
Obviously a driver who signs the station is wrong.

[royaloak]

9 hours ago, Banger Blue said:

i was going to include a link to the marker boards on the Railway Signs and Signals of GB website but it would appear the website owner has had a bit of a tantrum and thrown their teddies out the cot over the result of the General Election!! 
 

http://www.railsigns.uk/home.html

That is quite funny and does show the mentality of some of the 'other sides' voters.

 

There were a few errors on there anyway, although it was useful as a guide, it wasnt to be taken as gospel.

[royaloak]

3 hours ago, caradoc said:

Presumably the St Andrews Crosses at Temple Meads were installed due to being cheaper and easier to provide than mid-platform signals. Would it not be simpler to remove them and arrange the approach signals to clear to a main aspect if the platform is clear throughout or a subsidiary aspect if it is occupied ?

They always cleared to a single yellow if the indicated platform was clear but I appear to be wrong about that having posted the correct method of working and several posters ignoring it.

[phil-b259]

1 hour ago, jim.snowdon said:

I can imagine that being the case if there the signalling design had reached an advanced stage without any mid-platform signals, simply because change is expensive, particularly with the modern computer based interlockings. But, the use of mid-platform signals would have been an entirely logical feature - simple, straightforward and conforming to established practice.

The issue of zero (or more accurately significantly reduced) overlap is only an issue when the other half of the platform is already occupied by a train, and there are straightforward soluitions to dealing with negligible overlaps - London Underground had more than a few round parts of the Metropolitan/Circle Line.

I am, though, left with the impression that the arrangement at Bristol was a "how do we get ourselves out of a problem at minimum cost" solution.

 

Jim

 

My understanding is that the signalling at Bristol was not replaced in its entirety - it was ONLY the interlocking that was renewed. This has two big benefits :-

 

(1) It costs less as the only real change on the ground is the fitting of lots of new ID plates and data link modules which are connected to the existing signals, points, track circuits etc.

 

(2) If further remodelling happens its a lot easier to reprogramme a computer based interlocking than it is to perform open heart surgery on an old relay interlocking (which usually has issues with wire degradation or obsolete design practices due to its age).

 

Given at the outset it was envisaged that there would be a wholesale remodelling of the Bristol station area to co-incide with electrification, the changes at Bristol everyone is getting so stressed about were likely thought of as a 'inital' / temporary situation that would see further dramatic changes being made to the signalling and track layouts in the area plus the wholesale replacement of signals* etc.

 

The fact that cost overuns on the electrification scheme have probably caused cutbacks and the need to do the MINIMUM NR can get away with, then its likely Bristol is stuck with a 'interim' signalling setup which has resulted in a number of sub-optimal situations - particularly where an unmodified track layout does not co-incide with modern design standards.

 

 

* Converting signal heads to LEDs does NOT count as a resignalling! They can be swapped over with no interlocking changes and only the most minor of changes to location case wiring  in routine possessions.

Edited December 30, 2019 by phil-b259

[phil-b259]

9 hours ago, Zomboid said:

It's strange that essentially the same functionality has been achieved in such different manners at Bristol and Reading though.

 

Since I've seen 3 trains stacked up on the same platform at Cardiff I would imagine that's done in a different way again.

 

And then Southampton Central has the same functionality, which is probably a 4th entirely different approach...

 

Horsham is another oddball place.

 

The Southern Railway installed back to back mid platform signals in platform 4 during the 1938 rebuild as well as providing a call on facility into said platform for the joining ans splitting of trains . All well and good, however....

 

....Back in 1938 the Southern also allowed call on moves into another couple of platforms that did not have mid platform signals provided for the purposes of joining and splitting trains.

 

Now, certainly under BR (and later) it has been regular practice to use the call ons to platform share (even if units are not due to attach) which kind of makes the provision of mid platform signals on only platform 4 superfluous.

 

Come the mid 2000s when Railtrack / NR finally renewed everything (including the outside kit - not just the interlocking) they replicated EXACTLY the situation of 1938 with only one platform having back to back mid way signals - which rather begs the question why? Surely it sound be a case that either ALL platforms which can accommodate two trains should get them or none!.

 

Edited December 30, 2019 by phil-b259

[jim.snowdon]

10 hours ago, phil-b259 said:

 

Horsham is another oddball place.

 

The Southern Railway installed back to back mid platform signals in platform 4 during the 1938 rebuild as well as providing a call on facility into said platform for the joining ans splitting of trains . All well and good, however....

 

....Back in 1938 the Southern also allowed call on moves into another couple of platforms that did not have mid platform signals provided for the purposes of joining and splitting trains.

 

Now, certainly under BR (and later) it has been regular practice to use the call ons to platform share (even if units are not due to attach) which kind of makes the provision of mid platform signals on only platform 4 superfluous.

 

Come the mid 2000s when Railtrack / NR finally renewed everything (including the outside kit - not just the interlocking) they replicated EXACTLY the situation of 1938 with only one platform having back to back mid way signals - which rather begs the question why? Surely it sound be a case that either ALL platforms which can accommodate two trains should get them or none!.

 

Possibly a case of like for like renewal avoiding any design work (and minimising cost) and/or done in a hurry as a consequence of the age of the previous equipment?

 

Jim

[The Stationmaster]

On 29/12/2019 at 14:38, Grovenor said:

Not just a simple replacement though, the problem comes from allowing a yellow up to a signal with no overlap. Entering on a sub to the St Andrews cross should not have been at 25 anyway, IMHO. Incidentally would the sub in that case have had a special route indication?

The way it was done was more sophisticated that that as it happens.   Obviously a passenger train proceeding on a subsidiary had to have an indication of the route it was taking - otherwise it was not permitted to pass the signal without some additional verbal authority from the Signalman  Thus was achieved by the clever expedient of using different numbers to the platform each side of the St Andrews Cross - odd numbers at the east end and even numbers at the west end.  

Thus a train running into an empty platform from the east  would receive a clear main aspect with an even platform number showing in the theatre route indicator so the train could run into the platform line at a maximum speed of 25 mph being reduced consistent with coming to a stand at the correct spot  

But if the far end of the platform was occupied a train arriving from the east would get an approach released subsidiary with an odd platform number showing in the theatre indicator clearly advising the Driver that he had to go no further than the St Andrews Cross (and of course the normal meaning of a subsidiary with a route indicated also applied so no way should the train run at 25 mph). 

 

[The Stationmaster]

On 29/12/2019 at 14:55, Banger Blue said:

If we are talking about the signs at Reading, which are white circles with the black triangle in the middle, they aren’t classed as Signals they are simply  “rear clear” marker boards to indicate to the driver that the rear of their formation is in clear of a given point.

 

I’m not 100% sure but I think they don’t need to get permission from the PiC of the platform to move once in the platform, just the signaller. Depending on wether they stop at the marker board or carry on down to the platform signal will depend on the direction of their next move or if another unit is to attach.

 

i was going to include a link to the marker boards on the Railway Signs and Signals of GB website but it would appear the website owner has had a bit of a tantrum and thrown their teddies out the cot over the result of the General Election!! 
 

http://www.railsigns.uk/home.html

I get the impression that the Railsigns site has been hacked judging by what you now see on it.

[The Stationmaster]

18 hours ago, caradoc said:

Presumably the St Andrews Crosses at Temple Meads were installed due to being cheaper and easier to provide than mid-platform signals. Would it not be simpler to remove them and arrange the approach signals to clear to a main aspect if the platform is clear throughout or a subsidiary aspect if it is occupied ?

I got the impression at the time that it was seen as a pragmatic way round a difficult situation.  The 1930s resignalling had included some signals part way along some of the through platforms but they didn't do anything like dividing the platforms into equal lengths either side of the signals.  With increasing use of fixed formations and unit trains the old arrangement of intermediate signals which were probably more use for various shunting moves and attaching/detaching vehicles rather than anything else was probably seen as no longer needed.  But the platforms were in several cases plenty long enough to split into two parts and doing that would effectively increase capacity (which it did) plus it would allow a train to be brought into the rear of a platform to connect with one at teh further end of the platform (which it did).

 

I was working in South Wales at that time so now nothing about the story of the design but clearly a problem would be siting any intermediate signals without some hefty bits of civil engineering for some of them so some bright person came up with the idea of the boards which, as originally installed, didn't even need a power supply and could be easily suspended from part of the station structure - all of which meant they cost peanuts.  Somebody - perhaps the same one - then developed the idea of the split platform numbers to unmistakably note which end was which and using them in the route indicators.  Clever idea all round - except the original crosses weren't always easy to see so at some time illuminated versions came along.

 

The clever bit about it was that in signalling terms the first train could always run into the platform line at normal approach speed (hence part of the ability to increase speed to 25mph with the new track geometry) and even cleverer it meant that the second train coming in, on a sub, would always have a limiting point to how far it could run in on the platform line.

 

The fascinating bit with whatever is there now is how it compares with certain parts of the London area on former Southern Region lines where, as a signal engineer once explained to me, some of the overlaps are no longer than the thickness of a signal post.  I would thought, perhaps with 9 car IETS a potential problem?, there would be no difficulty in providing a 25 yard overlap at a mid-platform running signal at Temple Meads although such overlaps don't seem to be acceptable nowadays despite there probably still being plenty of them around.  But equally there would surely have been no real problem in retaining the 1970s arrangement which followed what are still usual principles of using a subsidiary to enter an occupied signal section.   Back to quantitive risk assessments, or not, once again I suspect?

[96701]

Just to get back to electrification, trains can now run between Cardiff and Newport under electric power. 

[rodent279]

On 25/12/2019 at 23:10, St. Simon said:

Hi

 

The change-over site at Severn Tunnel Junction is basically either side of the M4 Bridge (Pan down on the tunnel side, pan up on the Newport side), whilst the site at Pilning is either side of Pilning  station (Pan down on the tunnel side, pan up on the Bristol side)

 

There is also a pan down site on the approach to Patchway from Wales for trains via Filton Abbey Wood. But, due to the Severn Tunnel, if there are any Wales to Filton Class 80x’s, they will remain in Diesel from STJ to Bristol.

 

Regards,

 

Simon

Does anyone on here know when the Severn Tunnel will be energised, and trains can run on electric all the way between BPW & Newport?

 

Cheers N

[St. Simon]

6 minutes ago, rodent279 said:

Does anyone on here know when the Severn Tunnel will be energised, and trains can run on electric all the way between BPW & Newport?

 

Cheers N

 

May this year is the latest date I think.

 

Simon

[Peter Kazmierczak]

7 hours ago, St. Simon said:

 

May this year is the latest date I think.

 

Simon

 

just to clarify Simon, do you mean that it'll be done by May at the latest or that May is the most recent hoped-for date and it could be later than that? Thanks.

[St. Simon]

11 minutes ago, Peter Kazmierczak said:

 

just to clarify Simon, do you mean that it'll be done by May at the latest or that May is the most recent hoped-for date and it could be later than that? Thanks.

Hi,

 

May is the date that I most recently heard, but yes it could move outwards.

 

Simon

[billbedford]

There has been an article posted in the Rail Engineer about Steverton Bridge

[rodent279]

On 29/12/2019 at 18:51, DY444 said:

 

The difference was that under the old arrangement if the platform was occupied beyond the St. Andrews cross (or indeed anywhere) then the east/west gantry signal only cleared with a sub aspect.  Reliance was then placed on the driver obeying the rule book and proceeding in such a way that they could stop short of any obstruction. 

 

PS.  To summarise.  Under the old system trains were obliged to run at a slow enough speed to stop short of an obstruction only when the platform was occupied and they were required to stop at the St. Andrews cross or the obstruction whichever they got to first.  Otherwise the only constraint was the 25mph limit and the need to stop at the St.Andrews cross or beyond depending on the platform number.  All trains could depart at up to 25mph.  Under the new system everything is limited to 10mph irrespective of the occupancy of the platform and irrespective of whether it is arriving or departing.  

Just so I am clear about what is being discussed, are these the St Andrews Crosses, pictured to the left of the Voyager in this photo?