Paired by use or paired by direction

[Ianno87]

The Trent Valley north of Rugby has the unusual arrangement of up slow, up fast, down slow, down fast as far as Brinklow where it becomes three tracks (up slow, up fast, down) to Nuneaton before taking up the arrangement you describe of both slows on the outside. I work at Brinklow so 66s running bracket open after being held at the end of the down slow and trying to get to Attleborough without holding up the next Pendo is a regular sight and sound.

That arrangement also happens for a short section further north between Hartford Jn and Acton Bridge.

 

[plugwash]

Even in the same area, you can have some of the layout using one arrangement, while less than a mile away, you have the other arrangement...

And sometimes it switches from one to the other without a 2-track section in between.

For example immediately south of Manchester picadilly the lines are at least nominally paired by use, but through levenshulme/heaton cheapel/stockport the lines are paired by direction. Not sure exactly where the switchover between the arangements is.

 

[AndyPJG]

And sometimes it switches from one to the other without a 2-track section in between.

For example immediately south of Manchester picadilly the lines are at least nominally paired by use, but through levenshulme/heaton cheapel/stockport the lines are paired by direction. Not sure exactly where the switchover between the arangements is.

Slade Lane Jn

 

[SynthD]

To me paired by direction with stations built as two islands is best, as it best facilitates fast to slow interchange. Also makes it easier to add slow-line-only stations as side platforms.

Only with wide platforms, with a fence to keep people from the fast platform while high speed trains pass.

 

[Bletchleyite]

Only with wide platforms, with a fence to keep people from the fast platform while high speed trains pass.

Wide platforms certainly. No need for a fence any more than there is any need for one between MKC P3 and P4 or the equivalent at Watford - the fences are used at stations where fast trains do not routinely call.

 

[LNW-GW Joint]

The Trent Valley north of Rugby has the unusual arrangement of up slow, up fast, down slow, down fast as far as Brinklow where it becomes three tracks (up slow, up fast, down) to Nuneaton before taking up the arrangement you describe of both slows on the outside. I work at Brinklow so 66s running bracket open after being held at the end of the down slow and trying to get to Attleborough without holding up the next Pendo is a regular sight and sound.

That arrangement also happens for a short section further north between Hartford Jn and Acton Bridge.

The logic in both these cases, I believe, was that the original Down Slow track had been lifted from the previous 4-track layout, so needed reconstruction anyway.
They were therefore installed to higher standards for 125mph, while the adjacent track, previously the Down Fast, remained at 110mph and became the Down Slow.
It saved a full reconstruction of one track in each case.
Probably the result of "optioneering" on the WCRM project cost.

Another WCML oddity is the way the 4-track layout splits into 2x2 at Colwich.
The result is that today's 125mph Down Fast weaves left into the Down Stafford with a 65mph speed restriction, while the Down Slow (the former 110mph Down Fast, now also 125mph) has a straight run into the Down Stafford with a higher 90mph restriction.

 

[Ianno87]

The logic in both these cases, I believe, was that the original Down Slow track had been lifted from the previous 4-track layout, so needed reconstruction anyway.
They were therefore installed to higher standards for 125mph, while the adjacent track, previously the Down Fast, remained at 110mph and became the Down Slow.
It saved a full reconstruction of one track in each case.
Probably the result of "optioneering" on the WCRM project cost.

Also puts (in both cases) the Down Slow on the operationally favourable side, so that freights from Northampton / Northwich can enter it and wait for an onward path on the Down Fast, so don't have to get across the Down and and Up Fast 'in one go' (though at Rugby that's helped by the flyover at the south end)

 

[ijmad]

One disadvantage of paired by direction, especially up slow / up fast / down fast / down slow is that it's difficult to terminate traffic on the slows without having a blocking move across the fasts. Hence what went on at Stevenage with Platform 5 and the Great Northern being turned at Watton-at-Stone while some expensive infrastructure was built to work around the problem.

Conversely up fast / up slow / down slow / down fast could create problems for the express service if the up fast becomes blocked. This is occasionally seen on the Metropolitan Line on the tube where a block between Finchley Road and Wembley Park can leave a lot of trains stuck because the Met is unable to cross the Jubilee Line (which operates as the slow) to reverse. Even if the signalling systems were compatible I imagine it's still difficult to find paths to allow fasts to use slows to reverse in times of disruption.

 

[A0wen]

One disadvantage of paired by direction, especially up slow / up fast / down fast / down slow is that it's difficult to terminate traffic on the slows without having a blocking move across the fasts. Hence what went on at Stevenage with Platform 5 and the Great Northern being turned at Watton-at-Stone while some expensive infrastructure was built to work around the problem.

Conversely up fast / up slow / down slow / down fast could create problems for the express service if the up fast becomes blocked. This is occasionally seen on the Metropolitan Line on the tube where a block between Finchley Road and Wembley Park can leave a lot of trains stuck because the Met is unable to cross the Jubilee Line (which operates as the slow) to reverse. Even if the signalling systems were compatible I imagine it's still difficult to find paths to allow fasts to use slows to reverse in times of disruption.

BIB - Except weren't turnback sidings also constructed at both St Albans and Tring to allow the that move and to avoid blocking the slows ? An alternative approach is what was done at Welwyn Garden City when electrification took place that allowed a train to leave from the western bay platform (can't remember if it's 1 or 4 now as they renumbered them at some point), by building a flyover on the south side of the station.

The pair by direction makes sense on the ECML given that you have the 2 track section at Welwyn - if you didn't, you'd end up blocking the opposite direction at certain times when accessing one of the pairs.

 

[zwk500]

BIB - Except weren't turnback sidings also constructed at both St Albans and Tring to allow the that move and to avoid blocking the slows ? An alternative approach is what was done at Welwyn Garden City when electrification took place that allowed a train to leave from the western bay platform (can't remember if it's 1 or 4 now as they renumbered them at some point), by building a flyover on the south side of the station.

At both St Albans and Tring the tracks are paired by use (DF/UF/DS/US), so the issue was not blocking trains on parallel lines during crossing moves but trains following behind on the same line.

 

[A0wen]

At both St Albans and Tring the tracks are paired by use (DF/UF/DS/US), so the issue was not blocking trains on parallel lines during crossing moves but trains following behind on the same line.

Yes, understood that, but the point that was being made was that turnback when paired by use is less disruptive and doesn't need the kind of works done at Stevenage - my point was it's not that straightforward and depends on other factors e.g. how busy the line is to begin with.

 

[HSTEd]

If terminating slows is an issue, wouldn't the obvious solution be:

up fast, up slow, down slow, down fast

You have a single island platform a station where only slow trains will call, and two islands at stations where fast and slow will interchange?

 

[swt_passenger]

If terminating slows is an issue, wouldn't the obvious solution be:

up fast, up slow, down slow, down fast

You have a single island platform a station where only slow trains will call, and two islands at stations where fast and slow will interchange?

Yes, but only if your stoppers all finish their stopping patterns on the trunk route. Once they include services to branches as well they‘re better on the outside. Or one side if that’s where all the branches are…

 

[Steve Harris]

One disadvantage of paired by direction, especially up slow / up fast / down fast / down slow is that it's difficult to terminate traffic on the slows without having a blocking move across the fasts. Hence what went on at Stevenage with Platform 5 and the Great Northern being turned at Watton-at-Stone while some expensive infrastructure was built to work around the problem.

Apart from there never was a "blocking move across the fasts" at Stevenage !! The Down Slow was bi - directional from Langley Junction to Stevenage platform 4 (so no need to cross the fasts).

The problem at Stevenage was the time taken for a service from Langley Jnc - Stevange (P4 terminate, change ends, depart back to) - Langley Jnc which was constricting the capacity on the Down Slow.

The possible problem you pointed out is a very valid one, but your example wasn't really the best to prove the point I'm afraid ! Peterborough would of probably been a better example tbh.

Yes, but only if your stoppers all finish their stopping patterns on the trunk route. Once they include services to branches as well they‘re better on the outside. Or one side if that’s where all the branches are…

I think we can probably debate this topic to death and never really find an answer. As what works in one place is not suitable in the other. (Junctions being on different sides etc).
The only solution which comes close is "flying junctions" ie where one line goes over (or under) another without crossing on the flat. But to build these type of junctions now costs ££££ along with residents protesting that they don't want a dirty great big embankment at the bottom of the garden etc.

 

[A0wen]

Apart from there never was a "blocking move across the fasts" at Stevenage !! The Down Slow was bi - directional from Langley Junction to Stevenage platform 4 (so no need to cross the fasts).

The problem at Stevenage was the time taken for a service from Langley Jnc - Stevange (P4 terminate, change ends, depart back to) - Langley Jnc which was constricting the capacity on the Down Slow.

The possible problem you pointed out is a very valid one, but your example wasn't really the best to prove the point I'm afraid ! Peterborough would of probably been a better example tbh.


I think we can probably debate this topic to death and never really find an answer. As what works in one place is not suitable in the other. (Junctions being on different sides etc).
The only solution which comes close is "flying junctions" ie where one line goes over (or under) another without crossing on the flat. But to build these type of junctions now costs ££££ along with residents protesting that they don't want a dirty great big embankment at the bottom of the garden etc.

Paradoxically, for many years they did block the fasts, but a few miles further up when they ran to Letchworth and had to cross to the Cambridge branch on the level at Hitchin before the flyover was put in !

 

[Steve Harris]

Paradoxically, for many years they did block the fasts, but a few miles further up when they ran to Letchworth and had to cross to the Cambridge branch on the level at Hitchin before the flyover was put in !

Indeed. But Hitchin is NOT Stevenage, which was the example given! As I said.... "problem you pointed out is a very valid one, but your example" (Stevenage) "wasn't really the best to prove the point".

Actually the problem at Hitchin (which would of been a better example) wasn't just the via Hertford North services terminating at Letchworth Garden City, you also had the Kings Cross - Cambridge, Royston (back in the 80's) and Kings Lynn terminators aswell.

 

[A0wen]

Indeed. But Hitchin is NOT Stevenage, which was the example given! As I said.... "problem you pointed out is a very valid one, but your example" (Stevenage) "wasn't really the best to prove the point".

Actually the problem at Hitchin (which would of been a better example) wasn't just the via Hertford North services terminating at Letchworth Garden City, you also had the Kings Cross - Cambridge, Royston (back in the 80's) and Kings Lynn terminators aswell.

In fact Hitchin would have been a good example with a terminating service as well. After electrification to Royston when there was the Hitchin - Huntingdon DMU that had to cross over from the Up to the Down lines - blocking both fasts. Ironically BR introduced that problem because originally the shuttle originally ran from Hertford North to Huntingdon and was therefore out the way when it reversed - curtailing it to Hitchin introduced the problem !

 

[ijmad]

Well I may have misremembered the situation at Stevenage but at least it generated some conversation

 

[Steve Harris]

Well I may have misremembered the situation at Stevenage but at least it generated some conversation

Indeed!
As I said, what works in one location may not work in another.

 

[onlinespotting]

The alignment of fast and slow lines were part of the rationale for the closure of Norton Bridge I believe, the slow lines are not near the platform I believe or aren’t in once direction, presumably this changed following the restructure of the junction there

 

[The Planner]

The alignment of fast and slow lines were part of the rationale for the closure of Norton Bridge I believe, the slow lines are not near the platform I believe or aren’t in once direction, presumably this changed following the restructure of the junction there

Nope, it was always sandwiched between the Up Fast and the Up and Down Recess lines prior to the remodeling, so could have only been served by trains to/from Stone. The lines are effectively reversed now so the Up Fast is on the other side and the chord line is at the back. The only way it could be served is if you sent a train across the job at Doxey and used the chord, which defeats the point of the flyover. The lack of a bridge is secondary..

 

[norbitonflyer]

If terminating slows is an issue, wouldn't the obvious solution be:

up fast, up slow, down slow, down fast

You have a single island platform a station where only slow trains will call, and two islands at stations where fast and slow will interchange?

I can only think of two places where that is done - the Metropolitan/Jubilee Lines between Finchley Road and Wembley Park, and the SDWR Windsor route between Queenstown Road and Barnes. In both cases it allows the stopping services to use island platforms. The Great Central Railway's London Extension was built with island platforms and extra-wide bridges to allow fast tracks to be added later, but it never came to pass.

There used to be an unusual working arrangement between Loughborough Junction and Blackfriars. In the peaks the four tracks were paired by use, with the eastern pair used by trains towards Denmark Hill (mainly Catford Loop services) and the western by the Central Division services via Herne Hill and Tulse Hill (the ancestors of today's Thameslink Wimbledon Loop services, although destinations varied over the years - Holborn Viaduct - Norbury - Norwood Junction - Gipsy Hill - London Bridge for example). Off peak, all up trains used the eastern (Denmark Hill) up line and all down trains the western (Herne Hill) down line, up trains from the Herne Hill direction crossing over north of Loughborough Junction and back again south of Blackfriars, whilst down Catford line trains did the opposite. With only 2tph on each route this rarely led to any conflicts. I could see no reason for this other than to allow platforms 1 and 4 at Elephant & Castle to be closed off peak - all trains using the island.

 

[Ianno87]

, and the SDWR Windsor route between Queenstown Road and Barnes.

Although the actual use of the lines today is Down Fast / Down Slow / Up Fast / Up Slow.

 

[43096]

Although the actual use of the lines today is Down Fast / Down Slow / Up Fast / Up Slow.

And the actual designation of the lines is Down Slow / Down Fast / Up Fast / Up Slow.

 

[nlogax]

The flyovers at Camden / Euston essentially split a paired by use railway into three pairs, ie Fasts to/from low numbered platforms (line A and X), slows to the Wood (lines B&C), and fasts to/from high numbered platforms (lines D&E).

Lines C, D, E, and X are all bi-di out to Camden, with the result that you can do a fast to slow weave, and vice versa (A<>B up, C<>D down) on Camden bank without conflict. D is usually an up line, but can be used as a down for services from the central / high number platforms to the down fast if required without interfering with up traffic to the low numbers.

It really is a very well thought out layout. But then success has many fathers.

Am a bit late to this one, but could anyone recommend where I could find a detailed and current map of the Euston approaches? From a passenger perspective I have been long confused by where everything seems to go and it'd be good to make sense of it.

 

[Halifaxlad]

Funny enough it was only yesterday I was thinking about pairing the lines between York and Northallerton paired by speed rather than direction!

 

[Ianno87]

Am a bit late to this one, but could anyone recommend where I could find a detailed and current map of the Euston approaches? From a passenger perspective I have been long confused by where everything seems to go and it'd be good to make sense of it.

The OpenTrainTimes map is a good place to start: https://www.opentraintimes.com/maps/signalling/lec1

 

[nlogax]

The OpenTrainTimes map is a good place to start: https://www.opentraintimes.com/maps/signalling/lec1

Lovely stuff, thank you

 

[Bald Rick]

It takes a while to make sense of all the tunnelled, grade separated routes up at Camden / eastern side of Primrose Hill Tunnel too. And of course there is the old Up Empty Carrigae Line Tunnel - the rathole - which closed about 30 years ago.

 

[The Planner]

It takes a while to make sense of all the tunnelled, grade separated routes up at Camden / eastern side of Primrose Hill Tunnel too. And of course there is the old Up Empty Carrigae Line Tunnel - the rathole - which closed about 30 years ago.

Showing your age calling it the wood too