Midland Mainline Capacity

[21C101]

I hear a lot said about the midland main line being full.

I dont think it is. Officially it is full south of Harpenden, however that is largely caused by fast Thameslinks having to cross slow Thameslinks on the fast lines, not the four (six peak) per hour intercities on the fast lines. As there are only single lead ladders and the tracks are paired, this causes all sorts of capacity reducing conflicting movements.

It seems to me that it is quite easily solved though. Next time you resignal, realign the tracks in two places, so that most of the Thameslinks (and all the offpeak Thameslinks) don't need to cross slows on the fast lines.

At Camden Road it is six track to Hampstead tunnels through Kentish Town. so keep the fasts as the fasts and realign the slows and Thameslinks giving from left to right facing south.

• Up Thameslink Loop
• Up Thameslink
• Down Thameslink
• Down Thameslink Loop.
• Up Fast
• Down Fast

This would allow some Bedford trains to overtake stopping St Albans trains at Kentish Town

Similarly, abolish the little used goods lines north of Finchley Road as far as Cricklewood yard and realign the tracks as above, this would give the above configuration between Finchley Road and the north spur of the Cricklewood Triangle where the goods lines would now begin.

This would give a three mile long paired dynamic loop clear of the fasts, enabling most Bedford trains to overtake slow line trains and importantly allow all Bedford trains to call at West Hampstead (they can't at the moment due to holding up intercities).

Finally, electrify the goods lines from Cricklewood to Silkstream and increase linespeed of the down goods line. This would allow down Thameslinks that cross to the fast lines at Havercross Hill to cross to the slow lines again at Silkstream without needing to cross the up fast. Similarly a new up slow to up fast crossover would be installed south of the Silkstream flyover.

That would mean that the only Thameslink services still using the fast lines would be the four per hour peak hour only limited stop services (St A-Harp-Luton-Flit-Bed only) and the vast reduction in conflicting movements would significantly increase capacity.

 

[route:oxford]

Extra capacity would be good.

Especially with E-W link!

Bristol-Swindon-Oxfod-Milton Keynes-Luton Airport-London International(-Gatwick?)

 

[LLivery]

Its not exactly looming with capacity between Sharnbrook, Wellingborough, Kettering and (Corby-Manton) either. The single freight line from Sharnbrook though Findon Rd deport to Kettering really does restrict freight movements and the current single track via Corby doesn't really help either. The current EMT timetable isn't exactly brilliant to use all capacity either. The whole MML south of Kettering should really be at least four tracks again. After EWR opens and electrification four tracks is inevitable.

 

[The Planner]

The resignalling back in the 80s was done on the cheap and only provided the bare minimum too.

 

[edwin_m]

Interesting and looks do-able on a quick scan of the aerial maps.

I guess the crunch question would be whether the Thameslink off-peak fasts would catch up the slows if they all shared the two slow lines between Cricklewood area and St Albans, the fasts running non-stop and the slows serving all stations. The fasts might also be a bit slower because the slow lines have speed restrictions at some stations where they have to dog-leg round the middle platform.

Not sure where Havercross Hill is as is doesn't appear on my Quail map and this thread is the only relevant hit on Google. But would such a slow-fast move still be needed if there were extra "slow" tracks as described which would provide non-conflicting opportunities to overtake? Even if this isn't needed, electrifying what are now the goods lines between Cricklewood and Silkstream might allow a better Sunday timetable, since it could then assume use of four out of six electrified tracks rather than two out of four at present.

 

[Abpj17]

Why south of Harpenden? If anything it would be south of Luton or south of St Albans as that is where trains start and terminate?

"St A-Harp-Luton-Flit-Bed only" as someone who lives in Leagrave, I'm not fond of those services - you can get them but then have a 13 minute wait at Luton for a Leagrave train (in practice you wait at the London station instead and just hope the train isn't suddenly delayed or cancelled). Or you forget/miss that they don't call and have to double back at Flitwick :x The 'small' stations north of Luton don't have lifts yet either - so unfortunately the 'slow' line trains aren't popular with buggies/impossible for wheelchair as you need to cross bridges to exit the station. For fast line trains, there are no steps from the platform, you're dropped right at the exit.

And some of the above is academic while performance remains poor from a range of other factors; trains are routinely a few minutes out from their actual times which messes up any careful scheduling.

 

[edwin_m]

Why south of Harpenden? If anything it would be south of Luton or south of St Albans as that is where trains start and terminate?

The off-peak fasts normally use the fast lines south of Harpenden and the slow lines north of Harpenden.

 

[Muzer]

Surely St. Pancras is a major capacity bottleneck, at least for EMT services.

 

[21C101]

Interesting and looks do-able on a quick scan of the aerial maps.

I guess the crunch question would be whether the Thameslink off-peak fasts would catch up the slows if they all shared the two slow lines between Cricklewood area and St Albans, the fasts running non-stop and the slows serving all stations. The fasts might also be a bit slower because the slow lines have speed restrictions at some stations where they have to dog-leg round the middle platform.

Not sure where Havercross Hill is as is doesn't appear on my Quail map and this thread is the only relevant hit on Google. But would such a slow-fast move still be needed if there were extra "slow" tracks as described which would provide non-conflicting opportunities to overtake? Even if this isn't needed, electrifying what are now the goods lines between Cricklewood and Silkstream might allow a better Sunday timetable, since it could then assume use of four out of six electrified tracks rather than two out of four at present.

Sorry, Haverstock Hill. Basically the south end of the long tunnel from Finchley road where it widens back from 4 to six tracks.

My guess is that, with the track layout I outline, overtaking at Kentish Town would be for late/out of course running rather than scheduled and the normal overtaking would be between West Hampstead and Cricklewood.

North of Cricklewood you only have four stations, Hendon, Mill Hill, Elstree and Radlett, so there is not too much scope to hold up northbound unless silly route setting lets a slow out of Cricklewood right in front of a fast.

Southbound is more tricky as is St Albans where there is no bay and terminating trains can and do hold up following fasts that have crossed to the slows at Radlett.

I think I would remove a few parking spaces at Harpenden and turn the up slow platform into an Island. The new side of the Island would be the up slow with the existing up slow mainly used to turn back trains that now terminate at St Albans. The problem with that is that this would conflict with trains changing from fast to slow at Harpenden so additional crossovers would be needed north of Harpenden as a result.
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Surely St. Pancras is a major capacity bottleneck, at least for EMT services.

They've got four platforms to themselves for four trains an hour offpeak and six trains per hour in the peaks for an all "multiple unit" service (ie no locos running round)

Fenchurch St manages to fit 20+ an hour into four platforms.

 

[ChiefPlanner]

The W. Hampstead 6 tracking (passenger) was half looked at some years ago - along with a south end bay at St Albans (impossible now due to commercial development - and hard then as the solum is so tight.

Of course - a certain "company" thinks there is plenty of space south of St Albans to serve the proposed "Rail" terminal at Radlett / Napsbury. Still brewing away with another "decision" next February....

 

[Senex]

The resignalling back in the 80s was done on the cheap and only provided the bare minimum too.

The Leicester scheme was de-scoped and de-scoped to cut the cost to an absolute minimum. First proposals had four aspects throughout, better crossover speeds, and kept much more track on the ground. That was then cut back to end up with what was eventually done. Even at the very last minute there were further cuts, in that the Market Harborough re-alignment was taken out -- after the riding school had been given notice and cleared and the surveyors' pegs had appeared on what was to be the new alignment. Market Harborough Junction was to be north of the station on a section of new straight track, but ended up with the two crossovers on the sharp well-canted curve south of the station, and for a long time this proved a rather unreliable installation (not sure if it's better these days). The provision of proper bi-di signalling was kept in the scheme, but only after a careful re-assessment of cost and benefit. The restrictiveness of the three aspects has been a plague right from the start, with much less traffic on the line, especially on the approach to Wigston North Junction from the south.

 

[edwin_m]

The Leicester scheme was de-scoped and de-scoped to cut the cost to an absolute minimum. First proposals had four aspects throughout, better crossover speeds, and kept much more track on the ground. That was then cut back to end up with what was eventually done. Even at the very last minute there were further cuts, in that the Market Harborough re-alignment was taken out -- after the riding school had been given notice and cleared and the surveyors' pegs had appeared on what was to be the new alignment. Market Harborough Junction was to be north of the station on a section of new straight track, but ended up with the two crossovers on the sharp well-canted curve south of the station, and for a long time this proved a rather unreliable installation (not sure if it's better these days). The provision of proper bi-di signalling was kept in the scheme, but only after a careful re-assessment of cost and benefit. The restrictiveness of the three aspects has been a plague right from the start, with much less traffic on the line, especially on the approach to Wigston North Junction from the south.

Much of this will have to go in the next few years because I believe the AC immunisation was cut out as well - unless the re-locking and re-control in recent years has rendered it compatible. So there may be an opportunity to reduce the signal spacings although Market Harborough remodelling still doesn't seem to be on the cards.

 

[MCR247]

They've got four platforms to themselves for four trains an hour offpeak and six trains per hour in the peaks for an all "multiple unit" service (ie no locos running round)



Fenchurch St manages to fit 20+ an hour into four platforms.

5tph off peak: 2x NOT, 2x SHF and 1x Corby. And fenchurch st is hardly a fair comparison.

 

[Muzer]

Yeah, St. Pancras EMT services have a much longer turnaround time than Fenchurch Street's services - partially because the longer-distance trains will need more time to prep/clean/etc., and partially to ensure delays (more likely to be incurred on longer-distance services) can be absorbed and don't have a knock-on effect. I mean, only four or five platforms are used for Waterloo mainline suburban services, but much more for the longer-distance ones.

 

[21C101]

Yeah, St. Pancras EMT services have a much longer turnaround time than Fenchurch Street's services - partially because the longer-distance trains will need more time to prep/clean/etc., and partially to ensure delays (more likely to be incurred on longer-distance services) can be absorbed and don't have a knock-on effect. I mean, only four or five platforms are used for Waterloo mainline suburban services, but much more for the longer-distance ones.

I think they are getting round that by prep/cleaning them at Cricklewood?

 

[PeterY]

I've often thought that single lead ladders on the Midland (and Great Western) from fast to slow, must really restrict capacity in an emergency. I think Network rail got it right on the WCML with double lead ladders.

I don't know the timings but I'm guessing single lead ladders give signallers a real headache when either the fasts or slow lines are closed for an incident.

 

[Muzer]

I think they are getting round that by prep/cleaning them at Cricklewood?

Ah, OK. I haven't yet played SimSig West Hampstead so can't comment

 

[21C101]

I've often thought that single lead ladders on the Midland (and Great Western) from fast to slow, must really restrict capacity in an emergency. I think Network rail got it right on the WCML with double lead ladders.

I don't know the timings but I'm guessing single lead ladders give signallers a real headache when either the fasts or slow lines are closed for an incident.

They are indeed bit of a pain when a pair of lines gets obsructed as a four track to two track merge is throttled effectively by a single lead junction. I'm not sure that they all need doubling though.

Generally Up Thameslink trains go over at the ladder at the north end of Finchley Road Tunnel and down Thameslinks at the ladder at the south end. These ones are 50mph

Same in reverse at the other end. Up trains tend to cross over at Radlett with down trains going over at Harpenden. These are 40 but recently got some approach control (flashing yellow) so the train dosent get brought almost to a halt before crossing over.

Leagrave and luton ladders only get used in the peak, Bedford ladders only used by Thameslink in the peak and up MML trains calling at Bedford with the Flitwick ladders only used when something goes pear shaped.

I once managed a Full Ladder at Leagrave after a train got caped in the up slow then went back to Bedford on the down fast.

 

[edwin_m]

I think they are getting round that by prep/cleaning them at Cricklewood?

That may happen in the peaks (there are certainly several sets at Crickewood during the daytime) but as far as I'm aware the off-peaks stay in the platforms. The Nottingham fast waits for a couple of minutes over an hour, because this is the only off-peak HST working so it can't interwork with anything else. With a uniform fleet of EMUs after electrification it ought to be possible to get a few more trains per hour at St Pancras.

 

[Taunton]

Fenchurch St is hardly a fair comparison.

Yes, Fenchurch Street normally has its departures up on the board well before St Pancras would.

It's notable to see that the MML is quoted as "at capacity" when the bulk of their fleet is made up of only 5-car units, and the handful of 9-cars they once bought have been progressively stripped down to 8 and then 7-car. If they had 11 or 12 coach trains like served this route a generation ago, and those were all full, you might understand things a bit better.

 

[MCR247]

Tbh I'd never seen the MML referred to as "at capacity" before this thread. All I'd heard was the well known fact that 4 platforms isn't enough for the MML at St Pancras.

I think "at capacity" was referring to paths rather than saying that the line was actually full and needed something doing about it

 

[Qwerty133]

It's notable to see that the MML is quoted as "at capacity" when the bulk of their fleet is made up of only 5-car units, and the handful of 9-cars they once bought have been progressively stripped down to 8 and then 7-car. If they had 11 or 12 coach trains like served this route a generation ago, and those were all full, you might understand things a bit better.

To rid the line of 4 coach trains... no less coaches now than when the meridians were 9 coaches.
And the maximum length on the MML would be 10 coaches due to platform lengths.

 

[TheBigD]

They've got four platforms to themselves for four trains an hour offpeak and six trains per hour in the peaks for an all "multiple unit" service (ie no locos running round)...

EMT run 5 trains per hour to/from St Pancras... Even in the peaks it's usually only 5 per hour...

1600-1659 = 5 departures (1600, 1615, 1625, 1629, 1657)
1700-1759 = 5 departures (1700, 1715, 1730, 1745, 1757)
1800-1859 = 5 departures (1800, 1815, 1825, 1830, 1857)

 

[AM9]

I think they are getting round that by prep/cleaning them at Cricklewood?

So doesn't that double the number of movements with an ECS to/from Criclewood on every service?

 

[Bald Rick]

Making Radlett a double junction was looked at in advance of the renewal a few years ago. Basically, the junction as designed is squeezed in to the only place it can go that avoids curves, neutral sections, under bridges and stations. To make it double - or even raise the crossover speed at all - means the junction has to spread over two or three signal sections which triggers major resignalling and considerable OLE works.

Making better use of the lines at Kentish Town has also been looked at. Unfortunately it is not possible to get a turnout of the speed required for the northbound line between the top of the incline ex st Pancras LL and the start of the next tunnel. It could be done with a lower speed turnout, but that would actually reduce the capacity.

Proposals like this get examined regularly, they just don't make the 'press' if they are shown not to be realistic.
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All I'd heard was the well known railway myth that 4 platforms isn't enough for the MML at St Pancras.

Corrected that for you

 

[AM9]

Making Radlett a double junction was looked at in advance of the renewal a few years ago. Basically, the junction as designed is squeezed in to the only place it can go that avoids curves, neutral sections, under bridges and stations. To make it double - or even raise the crossover speed at all - means the junction has to spread over two or three signal sections which triggers major resignalling and considerable OLE works.

If the Helioslough thing goes ahead could the Radlett ladder be supplemented by another or even a dive-under as part of the fast line acces to the depot

 

[Class 170101]

It would be correct to say that Fenchurch Street uses the same number of platforms as St Pancras but the services types are different.

In terms of single lead crossovers, the GE has some of these so they have to be used in pairs - for example Forest Gate Jn and Maryland West. Bow Jn and Bethnal Green. Doubtless the same would apply on the MML.

In terms of the signalling what is the aspect configuration now? Three or four?

If its three the stopping distances must be interesting at 125 for a Meridian and even 110mph for a HST (or are they allowed to do 125 as well?)

 

[CallySleeper]

I think they are getting round that by prep/cleaning them at Cricklewood?

Around half a dozen EMTs will stable at Cricklewood between the peaks, otherwise there are literally only a few that might visit between services. Otherwise any prep and clean is done at STP.

And yes HSTs can also do 125mph.

 

[AM9]

In terms of single lead crossovers, the GE has some of these so they have to be used in pairs - for example Forest Gate Jn and Maryland West. Bow Jn and Bethnal Green. Doubtless the same would apply on the MML.

The ladders frequently used by Thameslink fasts on the MML are at Carlton Road and West Hampstead S, slow to fast (down) and Radlett Junction, (both ways but interlaced. Ususally Down fasts cross over to the fast lines at Carlton Road and Up fasts at West Hampstead, thereby crossing the Up fast in a lower speed area and clearing the Uop fast as soon as possible. The problem with the Radlett bi-directional ladders is that they are interlaced, so only one train can be switched per Up fast gap. If there was a second crossover nearby, probably fast to slow (down) they could both be used to reduce conflicts.

 

[Bald Rick]

The ladders frequently used by Thameslink fasts on the MML are at Carlton Road and West Hampstead S, slow to fast (down) and Radlett Junction, (both ways but interlaced. Ususally Down fasts cross over to the fast lines at Carlton Road and Up fasts at West Hampstead, thereby crossing the Up fast in a lower speed area and clearing the Uop fast as soon as possible. The problem with the Radlett bi-directional ladders is that they are interlaced, so only one train can be switched per Up fast gap. If there was a second crossover nearby, probably fast to slow (down) they could both be used to reduce conflicts.

Depends on the definition of 'nearby' but Harpenden and Radlett are effectively used as a pair.
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If the Helioslough thing goes ahead could the Radlett ladder be supplemented by another or even a dive-under as part of the fast line acces to the depot

There is a proposed dive under, from the slows. There is no proposed access to / from the fasts. When Helioslough realise how much it will really cost, they may well then try and wriggle out of a rail connection altogether.