Line pairings on a 4 track railway

[MarkyT]

Some routes have both, with a flyover/diveunder at the change approaching the terminus (for example SWML at Wimbledon and ECML just north of Copenhagen Tunnel on the approach to Kings Cross).

That only applied after the 1970s remodelling and electrification. Prior to that Holloway flyover was only for goods to get into Kings Cross Yard.

There was less need for passenger trains on the Up Slow to cross over the entire layout to get to suburban platforms however, as a fair proportion of the inner suburban service called at the short York Road platform on the east side of the terminus throat before disappearing into the tunnel on that side to the Widened Lines for Moorgate. Some freight also went through to the Southern via that route and the cross-London connection from Farringdon that subsequently became Thameslink but was freight-only for decades. Most up freight crossed the original Holloway Flyover to get to the large goods yards to the west of the line. Only freight used the westernmost bore of Copenhagen tunnel in the pre-1970s layout.

 

[Kilopylae]

In that example the interchange is beneficial to passengers arriving at Clapham from stations between Teddington & Earlsfield, whereas a DS-DF interchange would only benefit passengers coming from Waterloo or Vauxhall.

The function of Clapham Jn is transitioning between the SWR and SR networks so an up/up interchange would only be useful for passengers getting picky about their London Terminal

 

[edwin_m]

I had a brief chat with a local NR timetabling person some years ago about the Stockport area changes, which had certainly been postponed at that stage but I think not ruled out entirely. He was of the view that it would be operationally beneficial because there would be several places to cross trains over.

For example, any train coming in from the Buxton line currently has to cross both the Up lines towards Cheadle Hulme at Edgeley No2, so must wait until both of these tracks are clear, or have one or two Up trains checked for it to make this move. With the proposed down-up-down-up layout, it would only have to cross one Down line in the Edgeley area. If heading for the Piccadilly shed it wouldn't need to cross any further, but if heading for Piccadilly P14 there would have been several more crossovers onto the westernmost Down line before Piccadilly, and it could have used whichever of these caused least conflict. However, this would create a risk of short-notice re-platformings from one island to the other at Stockport if the signallers changed the booked crossing move from south to north of the station or vice versa, and the subway there isn't really up to handling large numbers of people rushing from one side to the other.

 

[jfollows]

I had a brief chat with a local NR timetabling person some years ago about the Stockport area changes, which had certainly been postponed at that stage but I think not ruled out entirely. He was of the view that it would be operationally beneficial because there would be several places to cross trains over.

For example, any train coming in from the Buxton line currently has to cross both the Up lines towards Cheadle Hulme at Edgeley No2, so must wait until both of these tracks are clear, or have one or two Up trains checked for it to make this move. With the proposed down-up-down-up layout, it would only have to cross one Down line in the Edgeley area. If heading for the Piccadilly shed it wouldn't need to cross any further, but if heading for Piccadilly P14 there would have been several more crossovers onto the westernmost Down line before Piccadilly, and it could have used whichever of these caused least conflict. However, this would create a risk of short-notice re-platformings from one island to the other at Stockport if the signallers changed the booked crossing move from south to north of the station or vice versa, and the subway there isn't really up to handling large numbers of people rushing from one side to the other.

That makes sense, but it's another example of sacrificing passenger convenience on the altar of operational convenience I think, so I'm glad it didn't happen.

EDIT Well, that's perhaps a bit harsh on reflection, the people designing this were trying to do something good, but I still feel that it was a huge amount of money for relatively little gain, so I'm still happy it didn't happen!

 

[edwin_m]

That makes sense, but it's another example of sacrificing passenger convenience on the altar of operational convenience I think, so I'm glad it didn't happen.

EDIT Well, that's perhaps a bit harsh on reflection, the people designing this were trying to do something good, but I still feel that it was a huge amount of money for relatively little gain, so I'm still happy it didn't happen!

I'm inclined to agree, though reducing operational delays is also good for passengers. However any gain from switching a train at short notice between the Stockport islands would be lost by waiting for all the passengers to find their way across - unless it was preferred to leave most of them behind...

 

[30907]

The function of Clapham Jn is transitioning between the SWR and SR networks so an up/up interchange would only be useful for passengers getting picky about their London Terminal

...and you would never manage an up/up cross platform interchange between the two networks without massive upheaval

 

[Route115?]

I can only think of two long (over 40 miles) stretches of Up-Up-D-D four track, that is the SWML from Waterloo & the ECML and both have flyovers so that the tracks are UDUD coming into the teminals, Waterloo & Kings X.

Can anyone think of other examples of long stretches of UUDD? (I would exclude in what are effectively long dynamic loops such as the WCML between Rugby & Stafford).

Are there any major terminii where the tracks are UUDD? Again exclude short relief tracks such as the fast lines coming into Waterloo.

The ECML has a flyover at Welwyn allowing reversing trains not to foul the fast lines. Can anyone think of any other similar examples?

 

[edwin_m]

I can only think of two long (over 40 miles) stretches of Up-Up-D-D four track, that is the SWML from Waterloo & the ECML and both have flyovers so that the tracks are UDUD coming into the teminals, Waterloo & Kings X.

Can anyone think of other examples of long stretches of UUDD? (I would exclude in what are effectively long dynamic loops such as the WCML between Rugby & Stafford).

Are there any major terminii where the tracks are UUDD? Again exclude short relief tracks such as the fast lines coming into Waterloo.

The ECML has a flyover at Welwyn allowing reversing trains not to foul the fast lines. Can anyone think of any other similar examples?

There is UUDD from east of London Bridge to the grade-separated junctions north of East Croydon, obviously not 40 miles though. At the London Bridge end that used to be sorted out on the flat, but the East London Line and Thameslink works introduced some grade separation.

 

[Benjwri]

Can anyone think of other examples of long stretches of UUDD? (I would exclude in what are effectively long dynamic loops such as the WCML between Rugby & Stafford).

Severn Tunnel to Cardiff?

 

[jfollows]

Are there any major terminii where the tracks are UUDD? Again exclude short relief tracks such as the fast lines coming into Waterloo.

As with Manchester London Road, Liverpool Lime Street was paired by direction (DDUU towards the terminus from Edge Hill from left to right) until the changes associated with electrification in around 1960, when it changed to its current arrangement of paired by use (DUDU).

 

[zwk500]

Can anyone think of other examples of long stretches of UUDD? (I would exclude in what are effectively long dynamic loops such as the WCML between Rugby & Stafford).

Not sure if you're thinking of an old layout, but Attleborough to Colwich is definitely UUDD 4-track, not dynamic loops. Colwich to Rugby is a full fast/slow in the Up direction, although I will grant you that Rugby-Brinklow in the down is effectively a dynamic loop (as is Crewe to Winsford). Whitehouse/Milford to Stafford is UDUD, along with Stafford-Crewe.

The ECML has a flyover at Welwyn allowing reversing trains not to foul the fast lines. Can anyone think of any other similar examples?

Purely reversing flyovers the only other I can think of is also on the ECML, at Harringay. There are flyovers to switch the a UUDD layout to UDUD near Wimbledon, New Cross Gate*, Finsbury Park, and Severn Tunnel Junction.

* - The New Cross Gate flyover could be argued to be more along the lines of Battledown Flyover/Worting junction, splitting a 4-track route into 2 separate 2-tracks, rather than reshuffling the track assignment.
Honourable mention to the proposed rebuild of Windmill Bridge Junction, which would have moved the London Bridge slows from UUDD to UDUD, grade-separated London Bridge and Victoria routing conflicts and grade separated the Fast/Slow crossovers on the UDUD London Vic lines, in between grade separating all the 2-track line junctions in between. It's not clear what level of that scheme is still going ahead.

Severn Tunnel to Cardiff?

Only UUDD for a few miles, before reverting to UDUD at LLanwern East. Given the flat junction at Severn Tunnel and short distance you could argue it's more just an elongated junction than actually switching to paired by direction.

 

[Greybeard33]

I had a brief chat with a local NR timetabling person some years ago about the Stockport area changes, which had certainly been postponed at that stage but I think not ruled out entirely. He was of the view that it would be operationally beneficial because there would be several places to cross trains over.

For example, any train coming in from the Buxton line currently has to cross both the Up lines towards Cheadle Hulme at Edgeley No2, so must wait until both of these tracks are clear, or have one or two Up trains checked for it to make this move. With the proposed down-up-down-up layout, it would only have to cross one Down line in the Edgeley area. If heading for the Piccadilly shed it wouldn't need to cross any further, but if heading for Piccadilly P14 there would have been several more crossovers onto the westernmost Down line before Piccadilly, and it could have used whichever of these caused least conflict. However, this would create a risk of short-notice re-platformings from one island to the other at Stockport if the signallers changed the booked crossing move from south to north of the station or vice versa, and the subway there isn't really up to handling large numbers of people rushing from one side to the other.

One issue with this is that the Buxton and Hazel Grove services currently provide two of the 4tph calls at Heaton Chapel and Levenshulme, with the Alderley Edge and Crewe stoppers providing the other two. If this continued, the Down Buxton and Hazel Grove trains would still have to cross both Up lines between Edgeley and Heaton Chapel. Possibly the Stoke and Chester services could take over the Down calls, but that would give a very irregular timetable at those two stations.

Also the two fast Hope Valley services both go to Liverpool via the CLC line, so would still need to cross the entire layout somewhere between Edgeley and Piccadilly.

Some of the fast Avanti/XC/TfW services would probably need to use the "Up Slow" from Piccadilly to Stockport, in order to overtake the stoppers that would have to use the "Up Fast" to call at Levenshulme and Heaton Chapel. This would create potential conflicts between Stockport and Adswood Road, with fast trains in opposite directions having to cross each others' paths.

All in all I am unconvinced that this change would bring a net benefit.

 

[Bald Rick]

Can anyone think of other examples of long stretches of UUDD? (I would exclude in what are effectively long dynamic loops such as the WCML between Rugby & Stafford).

Not sure if you're thinking of an old layout, but Attleborough to Colwich is definitely UUDD 4-track, not dynamic loops. Colwich to Rugby is a full fast/slow in the Up direction, although I will grant you that Rugby-Brinklow in the down is effectively a dynamic loop (as is Crewe to Winsford). Whitehouse/Milford to Stafford is UDUD, along with Stafford-Crewe.

it is definitely running lines, and not dynamic loops. It’s 32miles!

 

[jfollows]

One issue with this is that the Buxton and Hazel Grove services currently provide two of the 4tph calls at Heaton Chapel and Levenshulme, with the Alderley Edge and Crewe stoppers providing the other two. If this continued, the Down Buxton and Hazel Grove trains would still have to cross both Up lines between Edgeley and Heaton Chapel. Possibly the Stoke and Chester services could take over the Down calls, but that would give a very irregular timetable at those two stations.

Also the two fast Hope Valley services both go to Liverpool via the CLC line, so would still need to cross the entire layout somewhere between Edgeley and Piccadilly.

Some of the fast Avanti/XC/TfW services would probably need to use the "Up Slow" from Piccadilly to Stockport, in order to overtake the stoppers that would have to use the "Up Fast" to call at Levenshulme and Heaton Chapel. This would create potential conflicts between Stockport and Adswood Road, with fast trains in opposite directions having to cross each others' paths.

All in all I am unconvinced that this change would bring a net benefit.

The full proposal, posted in a different thread https://www.railforums.co.uk/threads/manchester-south-remodelling-proposals-historical.241695/ show four platform faces at Heaton Chapel and Levenshulme which get around some of the issues here.

On the basis of this full proposal I think it does bring benefit, but I suspect at significantly too high a cost. My feeling is that "the money" can probably be spent better elsewhere.

 

[miklcct]

In that example the interchange is beneficial to passengers arriving at Clapham from stations between Teddington & Earlsfield, whereas a DS-DF interchange would only benefit passengers coming from Waterloo or Vauxhall.

There is no need for people coming from Earlsfield to do a cross-platform interchange at Clapham Junction. If they want Waterloo they will continue on the same train, if they want the country they will change at Surbiton and/or Woking.

 

[zwk500]

Are there any major terminii where the tracks are UUDD? Again exclude short relief tracks such as the fast lines coming into Waterloo.

Just picking back up on this, The Windsor lines into Waterloo are UUDD all the way from Barnes, with a brief drop down to 3 tracks from Queenstown Road to Nine Elms Jn.

 

[gabrielhj07]

There is no need for people coming from Earlsfield to do a cross-platform interchange at Clapham Junction. If they want Waterloo they will continue on the same train, if they want the country they will change at Surbiton and/or Woking.

What time is saved by continuing on to Waterloo, as opposed to changing at Clapham?

 

[zwk500]

What time is saved by continuing on to Waterloo, as opposed to changing at Clapham?

It's irrelevant. The line pairing does not switch over to accommodate any interchange. It's about smooth operating at Waterloo.

 

[miklcct]

What time is saved by continuing on to Waterloo, as opposed to changing at Clapham?

I'm explaining that there should be no situation where the cross-platform interchange at Clapham is useful, because they are in opposite directions. People starting from Earlsfield won't change trains there if they need Waterloo because they will stay on the same train.

 

[gabrielhj07]

I'm explaining that there should be no situation where the cross-platform interchange at Clapham is useful, because they are in opposite directions. People starting from Earlsfield won't change trains there if they need Waterloo because they will stay on the same train.

Except that passengers arriving on P10 from commuter trains may change to long distance trains on P9 whilst avoiding London.

 

[Bald Rick]

I'm explaining that there should be no situation where the cross-platform interchange at Clapham is useful, because they are in opposite directions. People starting from Earlsfield won't change trains there if they need Waterloo because they will stay on the same train.

There’s a surprisingly large flow between Croydon and Kingston, who have a cross platform change in one direction.

 

[swt_passenger]

Except that passengers arriving on P10 from commuter trains may change to long distance trains on P9 whilst avoiding London.

But that’s still only a useful side effect, I doubt it would ever have been considered as a specific aim of the original project.

 

[M-Train]

There’s a surprisingly large flow between Croydon and Kingston, who have a cross platform change in one direction.

Is the congestion that bad that the X26 doesn’t help?