Congestion - a problem called Welwyn

[Lee_Again]

Here are my ideas to fix the problem, with some consideration for costs and planning permission.

1) Hertford Loop - 4 slow per hour. ALL 4 stop at Gordon Hill to allow a FAST service through. They stop again at Hertford to allow the next FAST through. The 4 FAST services would be the Thameslink (TL) services. The extra 4-6 minutes would make little difference and could be saved by the removal of the waiting time at Finsbury Park. This saves 4 paths per hour (pph) across the viaduct.

2) The 5 coach services of LNER/Grand Central/Hull trains MUST run as two pairs with splitting done either at a station or loop along the way. This would save another 1 (poss 2) pph.

3) Run Thameslink trains on the outside up/down very slows between Finsbury Park (FP) and Alexandra Palace, effectively grade separating those services from the mainline all the way to Langley junction. With the new platform 5 for the stoppers, keep the viaduct traffic on the fasts and the loop traffic on the slows, the TL services are grade separated from FP to Peterborough and Hitchin (for the Cambs services). That has a massive impact on timetable allowances across the viaduct even if no additional paths.

4) No freight south of Hitchin during the peaks

Let's spend some real cash...

5) Bring back the two tunnels north of KX and grade separate the TL services from the Canal tunnels to Finsbury Park (yes, a new flyover needed OR keep both up/down to the west side and deal with the connection at Alexandra Palace flyover - both up/down cross over the four mainlines) - Keeping TL away from the mainline effectively means two separate railways run in the same corridor but not mixing. Any delay in the TL core will not spread to LNER services.

6) if you have 4 slows from WGC and 4 from Hertford, put 4 to Moorgate and 4 through an enlarged connection with the NLL at Canonbury. So we'll have new services from South East London/Stratford to Hertfordshire opening up new travel opportunities.

Over to you...

 

[Aictos]

Two major problems is Gordon Hill and Hertford North are not set up to allow faster services to overtake stopping services at those stations.

Gordon Hill will need platform 4 reinstated which means track and signalling to be done then you've got the work on the north end to convert from bay to though platforms.

I believe the work is possible though.

Hertford North is rather more difficult because you have the pointwork at the south end of the station and a road bridge immediately at the north end of the platforms.

So you have to:

1. Replace the road bridge with one capable of taking 4 lines.

2. Build a line for the current unused platform face opposite platform 1 which has never seen any track which needs earthworks to be done.

3. Remodel the layout to convert from bay to though platforms.

All in all, it would cost £££ and a far more cheaper solution would be to install a Up to Down crossover in the DOWN direction at Molewood Junction with the existing Up to Down crossover in the UP direction kept then you could put a Stevenage bound stopping service into Platform 1 while a Stevenage bound non stopping service is routed via Platform 2.

The price of one crossover would pale in comparison to the costs of all the work needed that the OP has stated.

 

[swt_passenger]

There’s no track capacity remaining to run trains from the GN through to Canonbury and onto either the NLL or ELL. There’s no way to build grade separation, which is the solution that usually gets mentioned next.

I also believe, (from one of the Kings Cross remodelling threads), that most of the alleged Thameslink crossing conflicts at Belle Isle Junction are solved by the layout currently being built.

 

[Lee_Again]

Two major problems is Gordon Hill and Hertford North are not set up to allow faster services to overtake stopping services at those stations.

Gordon Hill will need platform 4 reinstated which means track and signalling to be done then you've got the work on the north end to convert from bay to though platforms.

I believe the work is possible though.

Hertford North is rather more difficult because you have the pointwork at the south end of the station and a road bridge immediately at the north end of the platforms.

So you have to:

1. Replace the road bridge with one capable of taking 4 lines.

2. Build a line for the current unused platform face opposite platform 1 which has never seen any track which needs earthworks to be done.

3. Remodel the layout to convert from bay to though platforms.

All in all, it would cost £££ and a far more cheaper solution would be to install a Up to Down crossover in the DOWN direction at Molewood Junction with the existing Up to Down crossover in the UP direction kept then you could put a Stevenage bound stopping service into Platform 1 while a Stevenage bound non stopping service is routed via Platform 2.

The price of one crossover would pale in comparison to the costs of all the work needed that the OP has stated.

Gordon Hill....I didn't say this would be free but we're comparing to the cost of building a new viaduct and tunnels. Gordon Hill would be easy enough to do with a bit of effort.
Hertford....again, yes some infrastructure work, and I'm aware of the layout, but a bridge, or even your solution, or both, would be cheap[ish].
Either way, and there are other options, running four fasts via the loop has many benefits including not having to touch Welwyn and saving LOADS of money (ok, to be pedantic, LOADS - these costs)

Canonbury - never say "there's no way"...people said that about a virus only last week !!!! ....I did say "Let's spend some real cash"....with money, most things are possible. New/bigger tunnel, grade separation, wider cuttings... all achievable. Maybe not desirable but that's a different question.

 

[30907]

Point 2 - entirely agree.
Point 4 - already happens.

Point 1 though - the extra 6 minutes on the TLs wouldn't go down well with commuters, even if you could cut a minute at FPK. You've also added 4-5 minutes to stations beyond Gordon Hill, and ditto to Watton, depending on headways.
To make it palatable, you would need to recast the timetable to improve frequencies to Stevenage (and beyond) and to Hertford, which uses up at least 2 of your 4 paths.

If such a step could be justified by traffic growth, you could work the Hertford Loop on a 15-min pattern as:
All stations Gordon Hill terminator (using Down Slow 1 with a new connection at Ally Pally)
Thameslink non-stop (DSL2)
Fast to Gordon Hill (DSL2?) and stations to Hertford/Stevenage.
This eliminates most of the engineering work, if not the resignalling.
I've roughly checked the timings (conveniently, there are diversions via the Loop this weekend) and it looks just about workable. How well it fits with actual demand may be another question.

 

[tbtc]

Here are my ideas to fix the problem

Okay, so what is the "problem" that you are trying to solve?

Insufficient capacity due to a two line bottleneck over the viaduct. Fair enough.

But if a proportion of the London - Leeds/ Newcastle services move to HS2 then that frees up a number of paths over Welwyn (presumably there'll be an increase in the number of services from London to Lincoln/ Hull to fill in some of the gaps at Grantham/Newark etc, but since a lot of the long distance services don't stop much south of York/Doncaster, the LNER paths don't need to be replaced on a 1:1 basis)

HS2 isn't going to relieve these services in the next decade, but it'd take several years to approve/ fund/ build the kind of things that you are suggesting, so there'd be a fairly limited timeframe between a flyover being opened and it's usefulness reduced somewhat by HS2 removing a few paths anyway.

Then there's the problem of where any additional services would go (given the additional capacity over the Digswell that your proposals would create) - to Cambridge or Peterborough? Is there really capacity north of Welwyn for more services (given the constraints of existing stoppers between Welwyn North and Cambridge/ Peterborough)? It's not as if the lines are four track all the way from Welwyn North to Cambridge/ Peterborough - you'd just be hitting the next bottleneck.

Don't get me wrong, it's a bottleneck, and I'm certainly not defending five coach trains getting scarce paths over it - there is a problem - I'm just not sure that you're going to be getting much use out of the infrastructure you're proposing before it gets overtaken by events elsewhere (sorry, bad pun!)

 

[Bald Rick]

How many paths does this proposal release into London, compared to the 2021 timetable proposal? (8tph long distance, 8 tph Thameslink, 4tph GN to Kings Cross, 12/14 tph to Moorgate.

To gain full marks, demonstrate your workings of platform occupation at Kings Cross, fast line capacity north of Huntingdon, and how Thameslink services will meet their paths into / out of the core with the extended journey times. Also demonstrate how much extra rolling stock is required for the TL and Mooorgate services tha5 have longer journey times.

Good luck!

 

[30907]

That's easy - you leave the FPK/KGX end unchanged and just recast the timetable all the way north (at least as far as Peterborough/Lynn). That's a trivial exercise
Seriously though, it might be prudent to wait for the next big timetable overhaul. I think the idea is worth keeping in mind for the medium term, though of course by then things may well have changed significantly.

To your other questions:
On stock, my version of the proposal would require 1 extra 700 for the diverted services (2 for flexibility). The Loop would require 1, probably 2 because my version with no looping may be more resource-heavy. The bigger requirement would be for stock to cover the additional paths via Welwyn (as upthread).

Platform occupancy would be an issue for said additional paths, assuming the core is at capacity in 2021. However, 12tph out of 11 platforms at KGX looks generous, even with 55min turnround for Newcastle and beyond, so 14 should be doable and even 16. I suppose I am used to SR style terminal working