Single line working through platforms

[Edwin_m]

1 hour ago, PortLineParker said:

Hi all,

 

Thanks for all the responses; some very useful information up above.

 

Yes, it is Stalbridge - my mistake. Looking on an OS map and photographs, the points don't seem to be particularly 'shallow' to allow higher speeds than normal. I'd expect a speed of around 10 or 15mph would have to be observed to avoid derailing.

 

 

Cheers,

 

PLP

As the right hand track has no signal alongside the one for the left hand track, it can only be used in the direction shown here.  

 

Edited April 9 by Edwin_m

[Wickham Green too]

12 hours ago, jim.snowdon said:

... trains running in to a loop should have the straighter route, the presumption being that trains running out of the loop would normally be starting from rest or at a low speed and would not be inconvenienced by any speed restrictions through the reverse curves at the end of the loop.

Interestingly, that's the opposite of the principle on the UndergrounD where stations are often on a hump - the entry rise being used to slow arriving trains and the dip from the platform end used to accelerate away.

[Cwmtwrch]

On 09/04/2024 at 02:45, Michael Hodgson said:

Highley Station (Severn Valley) has a loop but only one platform. so all trains use the main line....

It is possible for a passenger train to cross a goods train here, but the goods train has to be shunted into the loop.  It is not permitted to cross passenger train in this way.

Understandable in modern conditions on a preserved line where trains stop at every station. However, it is not necessarily a guide to what happened earlier. When the GWR inherited Llanbedr & Pensarn from the Cambrian it had one platform and a loop, with a level crossing over both lines, and a double-ended goods siding. In 1937 the GWR extensively resignalled the station, added FPLs to the loop and built a new box further along the platform to replace the Cambrian one, but no additional platform. A non-stop passenger could now cross a stopping passenger, but the new signalling also included the provision of advanced starters in both directions, presumably to make it possible for two stopping trains to cross, by extending station limits to allow the necessary movements without involving the adjacent boxes.

Edited April 10 by Cwmtwrch

[stewartingram]

2 hours ago, Wickham Green too said:

Interestingly, that's the opposite of the principle on the UndergrounD where stations are often on a hump - the entry rise being used to slow arriving trains and the dip from the platform end used to accelerate away.

"Hump" and "loop" are two different things. As described the Underground uses gradients to its advantage for slowing down and accelerating. However, previous answers up thread are describing loops, in the horizontal plain.

I must admit, I'm in the thought of the entry to a loop being straight, in both directions, with the exits being curved (to the right) via the points, as a train starting will be normally slower. However I accept there would be cases for a straight through " road, and a "loop!" curved at both ends.

[caradoc]

At both Kingussie and Aviemore, if there is no Down train to cross Up trains use the Down platform which has easier access. 

 

[Wickham Green too]

8 minutes ago, stewartingram said:

"Hump" and "loop" are two different things. ...

Indeed ! ................ it was the slowing down / speeding up aspect of things I was trying to compare rather than the physical orientation.

[Edwin_m]

40 minutes ago, stewartingram said:

I must admit, I'm in the thought of the entry to a loop being straight, in both directions, with the exits being curved (to the right) via the points, as a train starting will be normally slower. 

A modern multiple unit, driven according to modern "defensive driving" policies, may well have a rate of acceleration greater than the rate of service braking used in normal operation, so would be moving faster at the loop exit assuming the station is at the loop midpoint and speed restrictions allowed it.  

 

However, another reason for "straight entry" at loops is that a train approaching too fast has more distance to get under control before it hits the slow turnout at the far end of the loop.  

[Michael Hodgson]

1 hour ago, Cwmtwrch said:

Understandable in modern conditions on a preserved line where trains stop at every station. However, it is not necessarily a guide to what happened earlier. When the GWR inherited Llanbedr & Pensarn from the Cambrian it had one platform and a loop, with a level crossing over both lines, and a double-ended goods siding. In 1937 the GWR extensively resignalled the station, added FPLs to the loop and built a new box further along the platform to replace the Cambrian one, but no additional platform. A non-stop passenger could now cross a stopping passenger, but the new signalling also included the provision of advanced starters in both directions, presumably to make it possible for two stopping trains to cross, by extending station limits to allow the necessary movements without involving the adjacent boxes.

Back in the day it was not unusual for minor lines to be able to cross a passenger train only with a freight train.  This would be convenient if you had a passenger train booked at a very minor station whilst the daily pickup goods was doing its thing in the yard which depending could be sufficiently time-consuming to become a nuisance to passenger services, whether stopping or not.

 

Also FPLs don't necessarily lock the point in both positions.  It was not unusual to lock the point when set for one route (the passenger route) but not when set for the other (the goods loop).

 

Station limits is a concept applicable to double track lines, it doesn't really apply in the same way to single lines, and Advanced starters were fairly unusual on single lines.  This is because shunting onto the single line was more analogous to shunting on the wrong line in a double track station, where you would have to Block Back Outside Home Signal.  On single lines there is no distinction between blocking back inside vs outside - there's only blocking back.

 

You wouldn't need an advanced starter to allow an express to cross a stopping passenger.  What you would need is for FPLs to be provided for the points when set into either loop, and signals reading into both loops.  If you have a platform on only one of those loops, that's obviously the one used by the stopper, and the express takes the other - which means in one direction it's right hand running.

 

 

[meil]

On 09/04/2024 at 00:38, PortLineParker said:

Hi all,

 

Just a quick one; picture a hypothetical section of single track with a 2 platform station along its length. The line passes through the station and a loop is located on the Down side, something like below:

 

If a through train was approaching the station from the left and both lines were clear, would the train still pass into the left hand track to always be on the left hand side or would the through line be set? I was wondering as on the S&D Henstridge was one such station among a few and with trains such as the Pines Express passing through, would they have been given a straight run through or would they have had to slow to negotiate the points at either end of the loop? It sounds silly now I've typed it out but I've been thinking about it for a while and I wonder if anyone knew of any concrete practice or first hand knowledge?

 

Cheers,

 

PLP

You are not asking about Single Line Working you are asking about the Working of a Single line. Two completely different things.

 

To answer your real question - it depends and one line can be bi-directional and the other a dedicated route.

[Cwmtwrch]

3 hours ago, Michael Hodgson said:

You wouldn't need an advanced starter to allow an express to cross a stopping passenger.  What you would need is for FPLs to be provided for the points when set into either loop, and signals reading into both loops.  If you have a platform on only one of those loops, that's obviously the one used by the stopper, and the express takes the other - which means in one direction it's right hand running.

I agree entirely, but the advanced starters were added when the other changes were made. The original layout had FPLs on the points from main to loop at both ends. Whether they were 'main line only' at that stage I don't know, but making them 'both ways' would only need different locking; the new layout would have to be locked from scratch in the new box anyway. The added FPLs were all in the loop, for traps and the connections to the siding. The homes were replaced with equal height brackets at both ends so both lines could be used bi-directionally, with the possibility of a faster train overtaking a slower one as well as crossing it.

4 hours ago, Michael Hodgson said:

Back in the day it was not unusual for minor lines to be able to cross a passenger train only with a freight train.

The Cambrian main line didn't come into that category, especially in summer.

4 hours ago, Michael Hodgson said:

Station limits is a concept applicable to double track lines, it doesn't really apply in the same way to single lines, and Advanced starters were fairly unusual on single lines.  This is because shunting onto the single line was more analogous to shunting on the wrong line in a double track station, where you would have to Block Back Outside Home Signal.  On single lines there is no distinction between blocking back inside vs outside - there's only blocking back.

Crossing two stopping trains would require one train, after station work was finished, to back out into the section it had arrived from, after having surrendered the token on arrival. It can then pull forward into the loop; meanwhile the second train can be accepted with the  home on and the line set for the loop, and is then held at the home. One the first is in the loop, the second enters the platform and surrenders the other token, after which the signalman can offer both trains on to the next box. With the advanced starters the signalman can permit those movements himself; without them the backing move has to be authorised by the signalman at the other end and a token issued, and then returned once the movement is complete. There seems no other possible reason for adding advanced starters at a station which did not previously have them, but I'm open to correction. I think that this station was not the only one on the Cambrian where this procedure was followed, but can't remember where now, I'm afraid.

[The Stationmaster]

21 hours ago, Cwmtwrch said:

 

Crossing two stopping trains would require one train, after station work was finished, to back out into the section it had arrived from, after having surrendered the token on arrival. It can then pull forward into the loop; meanwhile the second train can be accepted with the  home on and the line set for the loop, and is then held at the home. One the first is in the loop, the second enters the platform and surrenders the other token, after which the signalman can offer both trains on to the next box. With the advanced starters the signalman can permit those movements himself; without them the backing move has to be authorised by the signalman at the other end and a token issued, and then returned once the movement is complete. There seems no other possible reason for adding advanced starters at a station which did not previously have them, but I'm open to correction. I think that this station was not the only one on the Cambrian where this procedure was followed, but can't remember where now, I'm afraid.

re highlighted text - NO!  An Advanced Starting Signal as at a single line crossing station really served only as a very obvious reminder to a Driver making a shunt move into the section  not to go any further (unless thesignal hab d been cleared or he had verbal ermission to pass it at danger) cleared).  

 

Thus advanced starting signals really serve no additional purpose so far as the arrangements, and Regulations, are concerned when it comes to occupying the single line for shunting purposes.  The critical thing is that the Regulations were required to be applied for a movement into the single line section and that section ends at the Home Signal protecting the single to s double line connection..  Even provision of an outer home signal made. no difference because it is situated in the single section.  And of course a token etc was not necessarily issued (or needed) and it was in any case impossible to issue a token if there was already a train  in the section which had a token, or when shunts were being made from both ends of teh section at the same time.  

 

How do I know that?   - I've done - and I shunted a 10 coach passenger into a section already occupied by a 3 car DMU (heading away from thestation where I shunted the 10 coach train)  but I did have to borrow the signal box copy of the General Appendix and read the relevant parts of it to the. Driver before he would comply with my instructions to shunt into the section.) 

 

Don't take any notice of the practice on some preserved railways - they are not the way it was normally done in BR days.

 

Little item to enlarge on something posted earlier - the GWR also used automatic token exchange equipment at certain crossing loops on the Minehead and Barnstaple branches following changes made in the 1930s to increase capacity on those lines.

[Philately]

A nugget of marginally relevant information from darkest Northumberland:  The Alnwick to Coldstream line (opened in 1887 and closed to passengers in 1930) was engineered for double track between Whittingham and Coldstream, and the actual single track was laid along the east side of the earthworks.  This meant that the main line through stations that had platforms on the west side only (e.g. Akeld, Glanton and Hedgeley) had to go through a crossover wiggle at each end of the platform, while the "straight" sections (on the east side) had trap points installed.  

 

The reason for the quirk was that the NER catered for the possibility that the line would become part of a proposed artery between Newcastle and Kelso via Belsay, Scotsgap, Rothbury and Wooler, which was of course never built.

 

[PerthBox]

On 09/04/2024 at 12:46, Michael Hodgson said:

Radio Electronic Token Block used on some long remote single lines (like the Highlands) had spring loaded points so that trains always entered the left hand track at crossing places, the radio equipment having superseded physical tokens.  There was no longer a signalman to work the points and signals. Departing trains had to trail through the points set for the other loop, the flanges forcing the points blades over, which returned under spring pressure. 

 

RETB uses hydro-pneumatic self-restoring points. These use a gas filled accumulator which operates a hydraulic actuator; there are no springs involved. As noted above certain locations on the West Highland line (Garelochhead, Ardlui, Taynuilt, Bridge of Orchy, Rannoch, Spean Bridge) are set up for right hand running to make it simpler to shunt sidings.

 

On 10/04/2024 at 12:25, caradoc said:

At both Kingussie and Aviemore, if there is no Down train to cross Up trains use the Down platform which has easier access. 

 

 

Similarly at Dunkeld the main line is bi-directionally signalled, so Down trains use it if there is no crossing booked. Huntly is bi-directionally signalled for both main and loop lines, with trains typically only using the Down platform unless crossing.

Edited April 13 by PerthBox

[55020]

1 hour ago, PerthBox said:

Similarly at Dunkeld the main line is bi-directionally signalled, so Down trains use it if there is no crossing booked. Huntly is bi-directionally signalled for both main and loop lines, with trains typically only using the Down platform unless crossing.

 

Inverurie had a similar layout until the line was recently "double-tracked".  The lines through the station where bi-directionally signalled by semaphores controlled by the local signal box.  Passenger trains would utilise the Down platform unless two passenger trains were crossing.

 

Dyce would also follow a similar pattern, but my impression was that the platform selection was a bit more random!  Perhaps it was a form of amusement for the signalman?

 

 

Steve

[PerthBox]

1 hour ago, 55020 said:

 

Dyce would also follow a similar pattern, but my impression was that the platform selection was a bit more random!  Perhaps it was a form of amusement for the signalman?

At Dyce they'd use the chip shop side unless crossing.

[Jeremy Cumberland]

20 minutes ago, PerthBox said:

At Dyce they'd use the chip shop side unless crossing.

I feel the story ought to continue:

...unless, of course, the signalman hadn't been given his tradtional free fish supper, in which case he'd run the train into the opposite platform so the passengers would go into the Railway Hotel instead.

[jim.snowdon]

3 hours ago, PerthBox said:

RETB uses hydro-pneumatic self-restoring points. These use a gas filled accumulator which operates a hydraulic actuator; there are no springs involved. As noted above certain locations on the West Highland line (Garelochhead, Ardlui, Taynuilt, Bridge of Orchy, Rannoch, Spean Bridge) are set up for right hand running to make it simpler to shunt sidings.

That's just a hydraulic spring. The important feature of that arrangement is that the return stroke of the actuator can be damped so that the switches return to the normal position quite slowly. It saves wear and wear on the mechanism as otherwise it would return to normal between the bogies on each carriage.

[PerthBox]

2 minutes ago, jim.snowdon said:

That's just a hydraulic spring.

Presumably in the same way that a car is just a petrol powered skateboard.

[Michael Hodgson]

4 hours ago, PerthBox said:

 

RETB uses hydro-pneumatic self-restoring points. These use a gas filled accumulator which operates a hydraulic actuator; there are no springs involved. As noted above certain locations on the West Highland line (Garelochhead, Ardlui, Taynuilt, Bridge of Orchy, Rannoch, Spean Bridge) are set up for right hand running to make it simpler to shunt sidings.

 

 

Similarly at Dunkeld the main line is bi-directionally signalled, so Down trains use it if there is no crossing booked. Huntly is bi-directionally signalled for both main and loop lines, with trains typically only using the Down platform unless crossing.

Yes, the effect of the hydraulic design means the points self-restore slowly and so there's less wear on wheel flanges and point blades than a simple mechanical spring would cause.

 

Bi-directional signalling of multiple track layouts is increasingly common in modern signalling schemes as it provides much greater resilience to cope with operational problems (such as by-passing a broken rail or overtaking a failed train) and it also means some types of infrastructure maintenance can be carried out at move convenient times (such as during daylight).  It also enables one track to be preferred over the other where that has operational advantages.  However it was extremely unusual in the UK in the days of traditional signalling.

[PerthBox]

 

20 hours ago, Michael Hodgson said:

However it was extremely unusual in the UK in the days of traditional signalling.

Bi-directional signalling was a feature of the mechanically signalled layouts at many crossing loops under Scottish Region Tokenless Block, such as Huntly, Dunkeld, Inveurie, Dyce, Aviemore, Dunkeld etc...

[Michael Hodgson]

39 minutes ago, PerthBox said:

 

Bi-directional signalling was a feature of the mechanically signalled layouts at many crossing loops under Scottish Region Tokenless Block, such as Huntly, Dunkeld, Inveurie, Dyce, Aviemore, Dunkeld etc...

The ScR tokenless block was relatively late - first used in May 1969 I understand. 

 

The WR version used in the rest of the country preceded it, quite a different design and method of operation.  I believe the WR's objective was to allow token to be obtained without the signalling being there full-time, so that he could be freed up to do other duties such as selling tickets, whereas the Scottish version was more like Absolute Block and just did away with the need for physical handling of tokens.  The other advantage of Tokenless block was that the section didn't need continuous track-circuiting.

 

Where a platform needed to be usable in both directions, direction lever working (different regulations) was common. 

 

 

[PerthBox]

1 hour ago, Michael Hodgson said:

The ScR tokenless block was relatively late - first used in May 1969 I understand. 

 

The WR version used in the rest of the country preceded it, quite a different design and method of operation.  I believe the WR's objective was to allow token to be obtained without the signalling being there full-time, so that he could be freed up to do other duties such as selling tickets, whereas the Scottish version was more like Absolute Block and just did away with the need for physical handling of tokens.  The other advantage of Tokenless block was that the section didn't need continuous track-circuiting.

 

The ScR Tokenless Block first came into use in December 1965 between Montrose South and Usan, and preceded the English version. It has far more in common with Electric Token Block than Absolute Block (working as, effectively, a pair of tablet machines without tablets). But I'm dragging the thread off topic now.

Edited April 14 by PerthBox

[The Stationmaster]

19 hours ago, Michael Hodgson said:

The ScR tokenless block was relatively late - first used in May 1969 I understand. 

 

The WR version used in the rest of the country preceded it, quite a different design and method of operation.  I believe the WR's objective was to allow token to be obtained without the signalling being there full-time, so that he could be freed up to do other duties such as selling tickets, whereas the Scottish version was more like Absolute Block and just did away with the need for physical handling of tokens.  The other advantage of Tokenless block was that the section didn't need continuous track-circuiting.

 

Where a platform needed to be usable in both directions, direction lever working (different regulations) was common. 

 

 

I never came across the SCr version of Tokenless Block butI understand that it had a number of differences from the WR version (with which I was - at times unfortuantely - intimately familiar for 4 years of my railway career.  WR Tokenless could be worked as 'open block' provided the 'box in advance turned its Acceptance  Switch to 'Accept' (then Signalman could go off and do something else although in reality that never happened with the potential ultimate exception of Templecombe).  So in that respect it too was like Track Circuit Block although how the Signalmen worked in reality was slightly different and trains were very often offered by rings on the box-tobox. 'phones and then accepted (provided they could be accepted of course).

 

The use of either Direction Levers or - in earlier times Interlocking Levers (subtly different from an acceptance lever) was long established practice at larger stations with signalboxes at each end although on the Western it seems not to have been used for passenger trains on platform lines (I'm open to further information on this latter point)

[TravisM]

On 09/04/2024 at 20:51, Steadfast said:

Weston-super-Mare is on a single line but has a loop and two platforms. Trains can use either platform in either direction. Both lines have the same limit of 25 mph, so there is no slowing to diverge over pointwork.

The limitation (as I recall slightly hazily from memory, it's not something that directly affects me but was an interesting nugget of info) is that London IETs turn back in the longer of the two platforms, so if there's one of those sat waiting, everything else will use the other platform.

 

Jo

 

As I grew up near Weston-super-Mare in the 70's, I was told by station staff there at the time that London bound and cross country trains, plus HST's generally used platform 2 (the station building side and longest platform) because they were generally the longest, and platform 1 was tight for a full length train with engine and coaches.

 

As I'm modelling St Bees in the present era and has a similar track plan with passing loop to what the OP has drawn out, the Carlisle to Barrow trains use platform 2 (station building side), and the return workings use platform 1.  It has a signal box and uses tokens from St Bees to Whitehaven and St Bees to Sellafield. 

 

Generally the signaller closes the road crossing gates and the Carlisle bound train arrives first on platform 1, then the signaller sets the route for the Barrow train via platform 2, and takes the token from the driver.  Then will walk to the end of platform 2 via the pedestrian bridge and waits for the Barrow bound train to arrive.  When it arrives, they swop tokens and the Barrow train is free to depart and the signaller walks back to platform 1 and hands the new token to Carlisle bound driver.  Once that is done, the signaller returns to his cabin to pull the signals off and the train can depart.  I've been told that it's not uncommon for the crossing gates to be closed up to 10 minutes should one train be late.

[Jeremy Cumberland]

1 hour ago, TravisM said:

Generally the signaller closes the road crossing gates and the Carlisle bound train arrives first on platform 1, then the signaller sets the route for the Barrow train via platform 2, and takes the token from the driver.  Then will walk to the end of platform 2 via the pedestrian bridge and waits for the Barrow bound train to arrive.  When it arrives, they swop tokens and the Barrow train is free to depart and the signaller walks back to platform 1 and hands the new token to Carlisle bound driver.  Once that is done, the signaller returns to his cabin to pull the signals off and the train can depart.  I've been told that it's not uncommon for the crossing gates to be closed up to 10 minutes should one train be late.

St Bees, like most passing loops, is only signalled for left-hand running.

 

I can't say that I have watched the St Bees signaller particularly closely, but surely they have to put each token through the instrument, which would change the sequence of operations (notably the signaller not taking the token from the driver of the Barrow train and giving it directly to the driver of the Carlisle train).

 

Also, if the up train is expected more than a couple of minutes after the down train (down trains are usually scheduled to arrive first), then the signaller often raises the level crossing barriers after the down train has stopped in the platform, and there is a signal at the Carlisle platform end specifically for this purpose.

 

I don't know what information the St Bees signaller has to know when to expect trains. Departure times from Sellafield and Whitehaven, certainly, but they are both some distance away (Sellafield particularly), which might well mean the signaller lowers the barriers prematurely, expecting a train to arrive when it has been delayed en route.