4 Tracking Welwyn Viaduct: could it happen?

[ess]

Would it be possible to 4-track at Welwyn? How could it be done?

 

[30907]

See posts 16 and 17 for a brief recent summary.
https://www.railforums.co.uk/threads/where-next-to-four-track.174042/

 

[InOban]

Grade 2* listed. Most of the gain could be achieved by extra tunnel bores to the North, so that trains calling at the North station wouldn't be blocking the fast lines.

 

[quantinghome]

Sure it's possible; we can do anything with enough time and resources. Should we do it? Probably not, or at least not until post-HS2 ECML traffic levels are known.

 

[DarloRich]

Would it be possible to 4-track at Welwyn? How could it be done?

Yes it could be done. Could it be afforded?

 

[kieron]

Yes it could be afforded, even when the government is still picking the fruit from the Bank of England's magic money tree. Should it be done?

 

[jon0844]

Could you rebuild Welwyn North Station by moving it southwards enough to build two islands, allowing stopping trains to keep the fast lines clear? Then make a multi storey car park to compensate for the loss of parking.

A satellite view suggests there could just about be enough land and distance to have two extra tracks.

It might be a cheaper way to get a little more capacity without new viaducts or tunnels.

 

[AndrewE]

Another earlier thread (https://www.railforums.co.uk/thread...sion-to-building-new-alignments.169915/page-2 - not the one linked above) explained that there is no capacity for trains further south so there is no point increasing the number of lines at Welwyn. It came as a surprise to me, especially as the EC "ML" is only 2 or 3 tracks form there to Peterborough.
If it was to be done I would go for a pair of tunnels coming out north somewhere like Woolmer Green.

 

[BelleIsle]

They actually made a start a few years ago. They completed a lot of vegetation removal before it got canned.

 

[adamedwards]

The problem would be the time taken slowing to enter the loops, as they would be very short and I suspect rules about loops and points near big drops.

My crayonista idea is a Welwyn Garden City North station on the west side of the line just south of the bridge. It would sit on top of a multistory car park to build it up the side of the embankment. A single reversible line would connect to WGC platform 4 which then gives access to the flyover. In the am peak trains would start from here with very limited southbound trains at Welwyn North, reverse in the evening. In exchange for a longer walk, people joining the train would get a seat as being first on.

 

[DynamicSpirit]

Sure it's possible; we can do anything with enough time and resources. Should we do it? Probably not, or at least not until post-HS2 ECML traffic levels are known.

Although waiting in principle sounds sensible, HS2 is unlikely to impact anything on the ECML until phase 2b is complete, which is scheduled for 2033. Given usual delays with infrastructure projects, it's probably not unreasonable to suppose it might well actually be 20 years away. Also, it seems implausible to me that HS2 would cause much reduction in service levels: Currently there are 5tph LNER services: Two to Leeds, two to Newcastle/Edinburgh/etc. and one all stops to Newark (sometimes extended to York). Plus the irregular Grand Central trains. Post HS2, the intermediate ECML stops will still need connections to the North, so we can immediately surmise that there will still be 1tph each to Leeds and York/Newcastle (With perhaps both trains now stopping everywhere between Peterborough and Doncaster). Add to that a whole range of destinations around Lincolnshire that aren't currently served because the paths are taken up by Leeds/Newcastle trains: So I could well imagine 1tph to Grimsby via Lincoln, 1tph to Grimsby via Scunthorpe and 1tph to Hull. With those services, we're already at roughly current traffic levels. Then growth at Cambridge could see a case for more frequent very fast London-Cambridge services. So it looks to me like a very safe bet that post HS2, traffic levels around the Welwyn viaduct will be at least as great as they are today - and that's before you consider the possibilities for frequency improvements on the local services. I'd conclude that 4-tracking would definitely be of considerable benefit for many decades into the future. (Although you still have the problem of the huge cost).

 

[stut]

It came as a surprise to me, especially as the EC "ML" is only 2 or 3 tracks form there to Peterborough.

The ECML is 4-track from Woolmer Green to Huntingdon North, isn't it?

 

[bramling]

The ECML is 4-track from Woolmer Green to Huntingdon North, isn't it?

Yes. North of Huntington it's three tracks as far as Holme (with an up loop at Connington), then two tracks from Holme to Fletton.

 

[AndrewE]

...Then growth at Cambridge could see a case for more frequent very fast London-Cambridge services. So it looks to me like a very safe bet that post HS2, traffic levels around the Welwyn viaduct will be at least as great as they are today - and that's before you consider the possibilities for frequency improvements on the local services. I'd conclude that 4-tracking would definitely be of considerable benefit for many decades into the future. (Although you still have the problem of the huge cost).

Bald Rick is adamant that the ECML is absolutely full south of Welwyn (as you seem to be saying too), so there's no point increasing capacity for anything from further north. Maybe some of the outer suburban semi-fasts will be siphoned off down another Crossrail to allow more long-distance trains access to London. Although we really do have to stop feeding London-land's habit of hoovering up the lion's share of transport investment.

The ECML is 4-track from Woolmer Green to Huntingdon North, isn't it?

Not quite the same as quadruple all the way to Doncaster is it?

 

[bramling]

Could you rebuild Welwyn North Station by moving it southwards enough to build two islands, allowing stopping trains to keep the fast lines clear? Then make a multi storey car park to compensate for the loss of parking.

A satellite view suggests there could just about be enough land and distance to have two extra tracks.

It might be a cheaper way to get a little more capacity without new viaducts or tunnels.

I'm not sure there's be much value in it, as by the time the train has berthed in the loop, the next train will have suffered such a signal check that the stopping train might as well have cleared the section.

If going for a compromise, it's rebuild the station and one of either the tunnels or the viaduct. There's also an added complication that any second viaduct, IIRC, more-or-less has to be on the east side in order to preserve unspoiled the view of the west side of the existing viaduct.

I'm not holding my breath for anything during my lifetime!

ISTR GNER gently floated the idea of closing Welwyn North station at one point, however it didn't really take off. Perhaps if desperately looking for a quick fix they could resite Welwyn North station to the south side of the viaduct, at the end of the four-track section.

 

[jon0844]

I think it would be quicker to four track the whole thing than attempt to close Welwyn North. The appeals and protests would probably make it cheaper to four track!

But perhaps if you keep running the service down to the station (and Knebworth) everyone will start using Stevenage or WGC, and then you'll be able to justify reducing the service frequency....

 

[bramling]

I think it would be quicker to four track the whole thing than attempt to close Welwyn North. The appeals and protests would probably make it cheaper to four track!

But perhaps if you keep running the service down to the station (and Knebworth) everyone will start using Stevenage or WGC, and then you'll be able to justify reducing the service frequency....

I'm surprised Welwyn North gets the peak service it does. I'd suggest numbers don't really justify more than the 2tph base KX-Cambridge/Cambridge North service. It only seems to get 4tph by historical quirk. Somewhere like Hitchin is much more deserving of a non-stop peak service, having somewhere approaching six times the usage.

Many Welwyn North users arriving by car would probably be happy to use Knebworth or WGC, of even Hertford North, if only parking was more convenient at these. This just leave the immediate Welwyn North catchment, which is actually fairly small, albeit I suspect many households will contain commuters attracted to the property by the nearby station.

 

[59CosG95]

Another earlier thread (https://www.railforums.co.uk/thread...sion-to-building-new-alignments.169915/page-2 - not the one linked above) explained that there is no capacity for trains further south so there is no point increasing the number of lines at Welwyn. It came as a surprise to me, especially as the EC "ML" is only 2 or 3 tracks form there to Peterborough.
If it was to be done I would go for a pair of tunnels coming out north somewhere like Woolmer Green.

Whereabouts would they start at the south end?
The gradients each way would be quite severe - so severe that IMHO the cheapest thing to do would be to build a new viaduct to the west and then add another pair of tunnels parallel to the existing ones.

 

[jon0844]

How about branching off around Stanborough Lakes and running two new lines alongside the A1(M) up towards Stevenage. No need to build an expensive viaduct or tunnels, and maybe even being able to open a new station for Old Welwyn at the same time! Obviously land would need to be purchased, but following the path of a road must be a little easier?

(This is of course posted without having any serious research).

 

[Bald Rick]

How about branching off around Stanborough Lakes and running two new lines alongside the A1(M) up towards Stevenage. No need to build an expensive viaduct or tunnels, and maybe even being able to open a new station for Old Welwyn at the same time! Obviously land would need to be purchased, but following the path of a road must be a little easier?

(This is of course posted without having any serious research).

Have a look at google maps!

 

[AndrewE]

Whereabouts would they start at the south end?
The gradients each way would be quite severe - so severe that IMHO the cheapest thing to do would be to build a new viaduct to the west and then add another pair of tunnels parallel to the existing ones.

I don't want to add yet more pressure for investment in the SE, but I'm sure it would be quite do-able (if it was worth it in terms of being able to handle the extra trains it would be sending into London..)
We are discussing the fast lines which by definition are generally to be kept clear of stopping trains, although it seem that the privileged denizens of this area have come to expect fast line service but calling at their local station.
If the rest of the line south could handle any more traffic to & from the north then I would point out that modern electric passenger trains don't have much of a problem with gradients - to the extent that I believe speed limits are applied on TGV routes when they cross a summit! Freights can be restricted to the slow/existing lines and expresses sent to dive down and back up as steeply as is needed for the geography.
So start as far south as necessary, even going down into the north side of the river Lea valley under the Police HQ or the sports park on the 2 1/2 " map. There is even a stadium of some kind adjacent to the track which could be borrowed. Once you set a tunnelling machine going I suspect that doubling the length of the drive gives just a marginal increase in the overall cost.

 

[Pigeon]

Grade 2* listed. Most of the gain could be achieved by extra tunnel bores to the North, so that trains calling at the North station wouldn't be blocking the fast lines.

All the arguments that being listed cabbages the idea that I've seen rely on an invalid premise: that any additional viaduct would necessarily be some modern monstrosity that would ruin the spectacle. Which isn't so at all. The thing to do is construct an additional viaduct which is identical to the existing one. (And the additional tunnels, of course, otherwise there'd be no point.)

 

[Meerkat]

Surely you build it modern, with slim pillars in line with the old pillars?
I am not having this untouchable listed nonesense - presumably if such delicate opinions existed back then the original would never have got built! The juxtaposition of Victorian and modern would add to the scene....

 

[A0]

How about branching off around Stanborough Lakes and running two new lines alongside the A1(M) up towards Stevenage. No need to build an expensive viaduct or tunnels, and maybe even being able to open a new station for Old Welwyn at the same time! Obviously land would need to be purchased, but following the path of a road must be a little easier?

(This is of course posted without having any serious research).

I won't dissent about your disclaimer at the bottom of your post.

The A1M between Welwyn and Stevenage is 2 lane - and needs to be extended to 3 and there's not really the space to do that.

Add in the hill as you come out of Welwyn heading northwards is surprisingly steep.

That's before the "link" you mention near Stanborough Lakes, which would probably involve demolition of a chunk of the Lakes (good luck with that) and various other challenges all of which make re-building the viaduct and Welwyn North area look simple.

It would probably be easier to branch the ECML south of Potters Bar, run a line north east through Northaw to join the Hertford Loop north of Cuffley and then quad the Hertford loop.

 

[alex17595]

Surely you build it modern, with slim pillars in line with the old pillars?
I am not having this untouchable listed nonesense - presumably if such delicate opinions existed back then the original would never have got built! The juxtaposition of Victorian and modern would add to the scene....

The Swiss have done something like this and it fits in very nicely.

https://www.google.co.uk/maps/@46.5...4!1spEZl9Jm6r6D6j2BGbekr-w!2e0!7i13312!8i6656

 

[DynamicSpirit]

So to clarify, what is the main objection to 4-tracking around Welwyn North? Is it mainly because the cost of building another viaduct and tunnels for the extra tracks is considered too great, or is it mainly because of heritage-related concerns about building next to the current viaduct?

 

[quantinghome]

Although waiting in principle sounds sensible, HS2 is unlikely to impact anything on the ECML until phase 2b is complete, which is scheduled for 2033. Given usual delays with infrastructure projects, it's probably not unreasonable to suppose it might well actually be 20 years away. Also, it seems implausible to me that HS2 would cause much reduction in service levels: Currently there are 5tph LNER services: Two to Leeds, two to Newcastle/Edinburgh/etc. and one all stops to Newark (sometimes extended to York). Plus the irregular Grand Central trains. Post HS2, the intermediate ECML stops will still need connections to the North, so we can immediately surmise that there will still be 1tph each to Leeds and York/Newcastle (With perhaps both trains now stopping everywhere between Peterborough and Doncaster). Add to that a whole range of destinations around Lincolnshire that aren't currently served because the paths are taken up by Leeds/Newcastle trains: So I could well imagine 1tph to Grimsby via Lincoln, 1tph to Grimsby via Scunthorpe and 1tph to Hull. With those services, we're already at roughly current traffic levels. Then growth at Cambridge could see a case for more frequent very fast London-Cambridge services. So it looks to me like a very safe bet that post HS2, traffic levels around the Welwyn viaduct will be at least as great as they are today - and that's before you consider the possibilities for frequency improvements on the local services. I'd conclude that 4-tracking would definitely be of considerable benefit for many decades into the future. (Although you still have the problem of the huge cost).

I believe current ECML capacity is 6 long distance high speed (LDHS) services per hour. The latest NR capacity report (http://orr.gov.uk/__data/assets/pdf...20-capacity-timetable-assessment-dec-2014.pdf) allows for 7 or 8 LDHS tph once the currently planned improvements are complete. I have no details but it's likely that the planned ETCS signalling will increase capacity further, and before HS2 opens. Post-HS2, the priority of ECML services will move towards connectivity and away from speed. So yes, I look forward to hourly trains serving Lincoln, Grimsby, Hull, York/Newcastle and Leeds, with a more intensive stopping pattern than at present, perhaps with more regular calls at Stevenage and even Finsbury Park (using the same logic as Old Oak Common and Stratford stations). This scenario, is likely to reduce the speed differential between the LDHS and Cambridge services, thus increasing the number of trains that could be run.

TL;DR there will be at least 8 LDHS slots per hour on the ECML post-HS2, maybe more. I'm pretty sure this will be enough to be getting on with. If it's not enough, and if it's the key bottleneck then sure, let's 4-track Welwyn.

 

[MarkyT]

Here's an idea for partial widening, with four tracks through Welwyn North station itself but only one additional new track north and south thereof through new single bore tunnels and over a new viaduct respectively. This concept removes the platforms from the fast lines and allows a stopping arrival at the same time as a fast is passing in the same direction. It also allows a Welwyn North stopper to depart on yellow very close behind a fast that has just passed the station.
http://www.townend.me/files/welwynviaduct.pdf

 

[A0]

So to clarify, what is the main objection to 4-tracking around Welwyn North? Is it mainly because the cost of building another viaduct and tunnels for the extra tracks is considered too great, or is it mainly because of heritage-related concerns about building next to the current viaduct?

A mix of all 3 probably - you'd either need 2 new tunnels or extensive re-build of the existing, the viaduct is listed and if you look on Google earth you'll see there's not a huge amount of space from the north end of the viaduct through the station area.

Out of interest and probably a question for somebody like @Bald Rick - what or is there a limit about having points in close proximity to something like Welwyn viaduct where there is a large drop if something happened?

 

[XDM]

Here's an idea for partial widening, with four tracks through Welwyn North station itself but only one additional new track north and south thereof through new single bore tunnels and over a new viaduct respectively. This concept removes the platforms from the fast lines and allows a stopping arrival at the same time as a fast is passing in the same direction. It also allows a Welwyn North stopper to depart on yellow very close behind a fast that has just passed the station.
http://www.townend.me/files/welwynviaduct.pdf

This is a great idea, which never occurred to me nor, much more importantly, to the authors of the report into various options for quadrupling all the way between Stevenage & Welwyn Garden City.
That report must have been at least 10/12 years ago & it concluded they were all too expensive. From memory it did not mention the viaduct listing as a problem.

The other virtue of MarkyT's excellent scheme is that it will not be a barrier to full quadrupling. Indeed it provides quadrupling through the critical Welwyn North station.