Paired by use or paired by direction

Ken H

Established Member
Joined
11 Nov 2018
Messages
2,516
Location
N Yorks
On the West Coast route, between London* and where the Northampton route diverges at Roade, there are 4 tracks. These are paired by use so from East to West you have up slow, down slow, up fast and down fast.

North of Rugby it is paired by direction, so from east to west you have down slow, down fast, up fast and up slow (Except for the short 3 track section south of Nuneation)

Is it railway geography that determines this, or historical accident? Or are there current operating reasons that favour 1 layout of another?

I can see the argument for paired by use for south of Roade as it allows a simple clean diverge for the northampton loop. But it comes at a cost as trains needing to 'weave' from fast to slow lines must cross a track for the opposite direction.

*ignoring the DC lines to Watford
 
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
64,465
Location
"Marston Vale mafia"
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.
 

The Lad

Member
Joined
22 Jan 2015
Messages
314
In areas with heavy freight traffic paired by use can be better. It depends.
 

LNW-GW Joint

Veteran Member
Joined
22 Feb 2011
Messages
15,216
Location
Mold, Clwyd
On the WCML, the slow lines are on the outside Rugby-Colwich and Crewe-Winsford. Also Adswood Road-Stockport-Manchester.
But adjacent everywhere else (Euston-Roade, Milton-Stafford-Crewe, Golborne-Wigan and Balshaw Lane-Preston).
Much of that was to do with how the routes were originally constructed.
The later 4-trackings were generally paired by use (and extended in the recent TV4 project between Tamworth and Armitage).
Apparently some thought was given to reversing the pattern between Stafford and Crewe in the WCRM programme, but decided against because of the impact at Crewe.
RT/NR did start reversing the layout through Stockport (so that the slows fed into the Airport line and P13/14 at Piccadilly), but gave up because of the signalling complications.
Hence we still have the "Stockport 5" absolute block sections signalling the original layout there.
 

steverailer

Member
Joined
15 Feb 2013
Messages
169
From a basic maintenance point of view paired by use is the best option, as you can close 2 lines to work on them, paired by direction needs all 4 lines blocked due to ALO working restrictions
 

70014IronDuke

Established Member
Joined
13 Jun 2015
Messages
2,860
From a basic maintenance point of view paired by use is the best option, as you can close 2 lines to work on them, paired by direction needs all 4 lines blocked due to ALO working restrictions

That's a very good point, and one that had slipped my mind - or perhaps I'd never thought of it.

I imagine paired by direction is the most natural way in most cases for four tracking to "evolve" as traffic builds up, because you start by adding loops at stations for easy overtaking, and then extend the slow lies to these as needed. But in the case of the Midland's four-tracking, I think the need for easier gradients in order to facilitate heavier mineral trains (specifically on the approaches to Sharnbrook summit) was the decisive factor.

That doesn't really explain why the GWR chose to be paired by use between PAddington and Didcot, however.
 

mr_jrt

Established Member
Joined
30 May 2011
Messages
1,159
There's also the question of which kind of paired by direction - slows in the middle or on the outside. In my mind, slows in the middle works best in urban areas, and fasts in the middle in more rural areas.

Slows in the middle enable you to have a single island platform for minor stations, reducing infrastructure required, along with enabling you to put in centre turnback sidings very easily wherever you like, particularly at stations where the lines are already separated for the platforms - no need for expensive fixed flyovers at turnbacks. Downsides are that the fast lines will have to deal with the "bump" from those minor stations, which can affect speeds. Obtaining the land required to ease the curvature could be tricky. Every branch will also require a single track bit of grade separation for a single fast line to go over or under it.

Fasts in the middle have the advantage that they will have the optimal alignment, so will be fastest with minimal land take as the slow platforms can be short bulges into the surrounding land without need for gentle track curvature. You will however still require a single track bit of grade separation for any branches, abet to get the opposite slow line over to the side of the branch instead of getting the fast line over both slows as before.

Paired by direction means you'll obviously always need some sort of grade separation for every branch whichever way is selected though (unless the lines are so lightly loaded a flat crossing is acceptable...but then you'd have to wonder why there are 4 tracks at all!)
 

edwin_m

Veteran Member
Joined
21 Apr 2013
Messages
20,701
Location
Nottingham
The only significant section of "slow in the middle" I can think of is the Met/Jubilee between Finchley Road and Wembley Park, where the "fast" Met lines aren't exactly fast in main line terms. Ironically this has the "paired by use" Great Central alongside it. Everywhere else the alignment difficulties of putting the slows in the middle seem to outweigh the operational benefits.

Originally the Midland had relatively little passenger but lots of freight traffic, so over most of their length what are now the Slow lines were actually Goods lines where permissive working was allowed and at times multiple trains could stack up nose to tail. So to some extent these were two separate railways. It's less suited to the current operation where the St Albans/Luton terminators stay on the slows and the MML stays on the fasts but there are also the Thameslink Bedford trains that are non-stop on the fasts to (generally) St Albans but then have to cross on the flat to use the slows further north. A flyover in the Harpenden area would be desirable but very difficult. On the other hand if the MML had been paired by direction it would have needed flyovers around Kentish Town, St Albans, Luton and Bedford to accommodate the present Thameslink service without major flat conflicts. Rather like the GN with flyovers at Kings Cross, Alexandra Palace, Welwyn, Stevenage and more recently Hitchin.
 

macka

Member
Joined
4 Oct 2012
Messages
31
From a basic maintenance point of view paired by use is the best option, as you can close 2 lines to work on them, paired by direction needs all 4 lines blocked due to ALO working restrictions
I believe that's why the Trent Valley has bidirectional signalling on the fast lines in the middle - it lets the lines switch over to paired by use so it can still operate if one of the lines is closed.
 

swt_passenger

Veteran Member
Joined
7 Apr 2010
Messages
24,742
Paired by use is better at a major terminus. Thats why once they’d finished most of the four tracking of the lines out of Waterloo, on a paired by direction basis, and mostly with grade separated junctions, they then had to provide a flyover near Wimbledon to switch back to paired by use on the final approach to Waterloo.
 

edwin_m

Veteran Member
Joined
21 Apr 2013
Messages
20,701
Location
Nottingham
Paired by use is better at a major terminus. Thats why once they’d finished most of the four tracking of the lines out of Waterloo, on a paired by direction basis, and mostly with grade separated junctions, they then had to provide a flyover near Wimbledon to switch back to paired by use on the final approach to Waterloo.
Similarly with the flyover just outside Kings Cross. Although Euston with its multiple grade separations shows that paired by use can also benefit from them.
 

Bald Rick

Veteran Member
Joined
28 Sep 2010
Messages
17,224
Similarly with the flyover just outside Kings Cross. Although Euston with its multiple grade separations shows that paired by use can also benefit from them.

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.
 

TBSchenker

Member
Joined
15 Sep 2010
Messages
548
Also Adswood Road-Stockport-Manchester.

One major pinch point is Slade Lane Junction where the running goes from paired by direction to paired by use - from Stockport to Slade Lane Jn it is Down Slow/Down Fast/Up Fast/Up Slow, and from Slade Lane Jn to Manchester Piccadilly it is Down Slow/Up Slow/Down Fast/Up Fast.

Between Stockport and Slade Lane Jn are Heaton Chapel and Levenshulme stations, platforms on the slow lines .To switch to paired by use from Adswood Road would mean the Down direction platforms remain on the Down Slow, but the Up Direction platforms would be on the Up Fast. Not a major problem if the linespeeds were similar, but I'm not sure what effect this would have on the Edgeley junctions south of Stockport.
 

Taunton

Established Member
Joined
1 Aug 2013
Messages
5,831
Believe it or not, Gerry Fiennes wrote about exactly this point, with diagrams, in a Trains Illustrated article in the late 1950s. His writing stated that by direction was the most effective on open line, and by use approaching the terminus to put the different users into their part of the station, with a flyover to achieve this near the terminus, was the most effective. In other words, the Waterloo approach. However, that seems to be unique. Somehow the LSWR shareholders also seemed able to fund all the flying junctions at the various divergences along the line as well, something that seems to have evaded their successors for the few that remain to be sorted.

It (Camden) really is a very well thought out layout.
It principally just builds on what the LNWR did in 1920 when the DC Line was built. I don't believe they actually added a single flyover, just made use of those which there for the carriage lines etc. It had paired arrivals (and ecs out) on the east, departures (and ecs in) on the west, and in/out locals in the middle. Fiennes was impressed with this one as well.

Fiennes did a brilliant spiders' web diagram of all the conflicts at Kings Cross, and called it "in contrast a mess". He was GN Line Manager at the time, of course. Never one to mince his words, and knowing the BR board would avidly read his article in the magazine first, was quite likely angling for something he had proposed :) . Eventually that caught up with him, but he seemed to have fun along the way.
 
Last edited:

John Webb

Established Member
Joined
5 Jun 2010
Messages
2,081
Location
St Albans
.......Originally the Midland had relatively little passenger but lots of freight traffic, so over most of their length what are now the Slow lines were actually Goods lines where permissive working was allowed and at times multiple trains could stack up nose to tail. So to some extent these were two separate railways. It's less suited to the current operation where the St Albans/Luton terminators stay on the slows and the MML stays on the fasts but there are also the Thameslink Bedford trains that are non-stop on the fasts to (generally) St Albans but then have to cross on the flat to use the slows further north. A flyover in the Harpenden area would be desirable but very difficult. On the other hand if the MML had been paired by direction it would have needed flyovers around Kentish Town, St Albans, Luton and Bedford to accommodate the present Thameslink service without major flat conflicts. Rather like the GN with flyovers at Kings Cross, Alexandra Palace, Welwyn, Stevenage and more recently Hitchin.
The history of the Midland main line, particularly the 'London Extension' (opened 1868) is rather complex. The Midland Railway built the latter in stages as they didn't have the money to lay all four tracks from Bedford southwards in one go. They bought the land, but at first only built the current Fast lines, followed by an 'Up Freight' line, started in 1875. By the 1890s both freight and passenger traffic needed more space and the present slow lines were built from St Albans southwards and opened at first only to freight. But with the completion of the second Elstree Tunnel in 1895 the goods lines became the slow lines and handled passengers as well from South of St Albans.
Meanwhile work also progressed northwards on doubling up the goods lines - by 1894 these extended from Harlington down to Elstree.
In 1906 the goods lines from St Albans to north of Harpenden were converted to passenger working with new platforms at St Albans City and Harpenden stations. The goods lines to Bedford were not converted to passenger use until the introduction of the DMU service in 1960.
So the pairing of the MML is mostly due to economic factors.
 

Bald Rick

Veteran Member
Joined
28 Sep 2010
Messages
17,224
Believe it or not, Gerry Fiennes wrote about exactly this point, with diagrams, in a Trains Illustrated article in the late 1950s. His writing stated that by direction was the most effective on open line, and by use approaching the terminus to put the different users into their part of the station, with a flyover to achieve this near the terminus, was the most effective. In other words, the Waterloo approach. However, that seems to be unique. Somehow the LSWR shareholders also seemed able to fund all the flying junctions at the various divergences along the line as well, something that seems to have evaded their successors for the few that remain to be sorted.

It principally just builds on what the LNWR did in 1920 when the DC Line was built. I don't believe they actually added a single flyover, just made use of those which there for the carriage lines etc. It had paired arrivals (and ecs out) on the east, departures (and ecs in) on the west, and in/out locals in the middle. Fiennes was impressed with this one as well.

Fiennes did a brilliant spiders' web diagram of all the conflicts at Kings Cross, and called it "in contrast a mess". He was GN Line Manager at the time, of course. Never one to mince his words, and knowing the BR board would avidly read his article in the magazine first, was quite likely angling for something he had proposed :) . Eventually that caught up with him, but he seemed to have fun along the way.

I was referring to the whole Euston layout, not just Camden.

As an aside, why are the suburban platforms called the Wood?

I’ll refer to @ChiefPlanner
 

ChiefPlanner

Established Member
Joined
6 Sep 2011
Messages
6,505
Location
Herts
I was referring to the whole Euston layout, not just Camden.



I’ll refer to @ChiefPlanner

Because the old DC platforms were , in fact . wooden - up to the rebuilding in the 1960's , one of these wonderful legacy terms carried on - to the extent that the DC lines supervisors were always referred to as such.
 

Helvellyn

Established Member
Joined
28 Aug 2009
Messages
1,650
Somehow the LSWR shareholders also seemed able to fund all the flying junctions at the various divergences along the line as well, something that seems to have evaded their successors for the few that remain to be sorted.
They even had the land ready for the flyover at Woking to grade separate traffic coming off the Up Portsmouth but BR sold it for housing. Had it been built there would have been no need for platform 3 at Woking.

Interestingly when the LSWR went to four tracks they went for paired by direction even though it had originally been a two track railway. However, West of Basingstoke they switch from being fast/slow to Sailisbury/Southampton. Hence the nice fishtail effect as an Up train comes off the Up Southampton and joins the Up Salisbury at Worting Junction that is then the Up Fast into Basingstoke.
 

HowardGWR

Established Member
Joined
30 Jan 2013
Messages
4,909
..... Hence the nice fishtail effect as an Up train comes off the Up Southampton and joins the Up Salisbury at Worting Junction that is then the Up Fast into Basingstoke.
Any idea what the speed limit is to take that junction (to join what is now the Up Fast)?
 

Inversnecky

Member
Joined
1 Jan 2021
Messages
454
Location
Scotland
I'm a bit confused about the arrangement of up, down, fast and slow lines.

In some cases, I have seen ("left to right") - up fast, down fast, up slow, down slow (i.e fast and slow either side of the "middle"). But in other cases it's been up slow, up fast, down fast, down slow (i.e., fast lines together in the middle to perhaps go through a non stopping station).

Is there a normal pattern to this? Or is it purely dependent on the local requirements (eg station layout)?

Perhaps I'm looking for a standard when there is none?
 

MadMac

Member
Joined
13 Jun 2008
Messages
319
Location
Moorpark, CA
Ah, the old "paired by direction" and "paired by use" thing. Basically, different railway companies had their own preferences. Example: the ECML four-track sections have both Ups together, whereas the GW is Slow (or Relief) together.
 

Flange Squeal

Member
Joined
17 Jul 2012
Messages
500
The lines out of Waterloo are good for this.

On the 'Main side', it is Down Slow, Up Slow, Down Fast, Up Fast as you head out.... until just beyond Earlsfield, where a flyover crosses the Up Slow over the fasts to give a Down Slow, Down Fast, Up Fast, Up Slow arrangement.

On the 'Windsor side', you start with Down Slow, Down Fast, Up Fast and Reversible. Beyond Queenstown Road the Reversible becomes the Up Slow, giving the Down Slow, Down Fast, Up Fast and Up Slow arrangement as per the 'Main side' beyond Earlsfield, described above. In reality though, the Down Fast is generally used by stopping services, and the Down Slow used by faster services. I believe this is to reduce conflicting movements at Barnes, where by the faster services using the Slow and stoppers using the Fast means the stoppers that "turn right" onto the Hounslow loop don't have to cross in front of the faster services (Readings/Windsors) which tend to all continue straight towards Richmond.
 

Taunton

Established Member
Joined
1 Aug 2013
Messages
5,831
On the 'Windsor side' ... In reality though, the Down Fast is generally used by stopping services, and the Down Slow used by faster services. I believe this is to reduce conflicting movements at Barnes
Same long applied east of Taunton, widened in the 1930s for the several miles out to Cogload Junction where the Paddington and Bristol lines split. Although designated conventionally, Main in the middle and Relief on the outside, they were always run that Paddington services used the middles and Bristol trains, which had the more frequent fast expresses, on the outside, down Bristol services using the flyover at Cogload. This extended right through to the platform usage at Taunton, Paddington on the centre island and Bristol on the outers. It also suited loading of mails, which were always heavier to Bristol and the North. Immediately west of the station things changed by the crossovers there, all expresses on the main and all locals on the outside Reliefs. This usage lasted until out to Cogload was reduced to double track in the 1980s.

There were high speed (well, 50 mph) crossovers at Cogload for Bristol trains to gain the main lines, but I never heard of a passenger service using them. They were used however by slow Up freights for Bristol, from the goods loop and yards on the south side by the station, running on the Up Main, enabling a Bristol express to pass on the Up Relief, and the freight crossing over to follow.
 

Annetts key

Member
Joined
13 Feb 2021
Messages
148
Location
West is best
Is it railway geography that determines this, or historical accident? Or are there current operating reasons that favour 1 layout of another?
Determined by local conditions, the required junctions, the type of traffic and history. Also keep in mind that for the most part, mechanical signalling was only suitable for unidirectional working.

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...

With modern signalling, now, if wanted, you can have four bidirectional lines, all with the same line speed and capacity (unless there are local or geographical reasons, such as station platforms causing curves that otherwise would not be required). Obviously the location of junctions and the arrangements at these junctions also affects things.
 

Snow1964

Member
Joined
7 Oct 2019
Messages
720
Location
West Wiltshire
On the South Western the 1930s widening associated with new docks (Southampton tunnel to west of Millbrook) was done opposite way to Wimbledon-Basingstoke as the slows lines are in the middle, and Millbrook now only has an island platform on centre pair of tracks. Although this bit is rather complicated as there are goods lines and loops outside the fast tracks

With paired by use Earsfield-Waterloo means there are 3 variations within 80 miles on same line
 

Aictos

On Moderation
Joined
28 Apr 2009
Messages
9,824
From a basic maintenance point of view paired by use is the best option, as you can close 2 lines to work on them, paired by direction needs all 4 lines blocked due to ALO working restrictions
Pretty much why I prefer paired by use to paired by direction simply because as you pointed out you can close two lines for engineering works and still be able to run a rail service over the two open lines which is something you cannot do with paired by direction lines as you need a complete line block and operate rail replacement buses.
 

david_g

Member
Joined
16 Mar 2013
Messages
44
Location
Warwickshire
On the West Coast route, between London* and where the Northampton route diverges at Roade, there are 4 tracks. These are paired by use so from East to West you have up slow, down slow, up fast and down fast.

North of Rugby it is paired by direction, so from east to west you have down slow, down fast, up fast and up slow (Except for the short 3 track section south of Nuneation)
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.
 

Top