Upgrading the Chiltern Line

[43074]

Isn't the benefit of connecting an underserved commuter line to a through-running core with spare capacity fairly self-evident?

I'm not sure the Chiltern line counts as an "underserved commuter line" these days, Marylebone gets 11.8 million entries/exits a year and that demand is coming from somewhere

 

[zwk500]

What stopping patterns would this infrastructure support?

I don't know until we've properly scoped out the study with the requisite objectives, inputs, assumptions, exclusions, and deliverables.


Then I'll be able to provide you with a timescale for an answer, and fee of course

 

[The Planner]

I don't know until we've properly scoped out the study with the requisite objectives, inputs, assumptions, exclusions, and deliverables.


Then I'll be able to provide you with a timescale for an answer, and fee of course

£110 an hour is the going rate.

 

[brad465]

I'd improve the signalling north of Risborough up to Aynho if it were me.

Having just looked at its composition I have to agree, it appears to be a mixture of 2 and 3-aspect throughout rather shockingly.

 

[150219]

Having just looked at its composition I have to agree, it appears to be a mixture of 2 and 3-aspect throughout rather shockingly.

Risborough to Bicester South is not so bad since the last resignalling. Bi-di is however quite restrictive. It's not so difficult to maintain 100mph with a good separation with the existing timetable and allows for some gaps to fit other moves well enough.

I agree with @The Planner for Bicester North to Aynho for both normal direction running and especially bi-di.

 

[The Planner]

Risborough to Bicester South is not so bad since the last resignalling. Bi-di is however quite restrictive. It's not so difficult to maintain 100mph with a good separation with the existing timetable and allows for some gaps to fit other moves well enough.

I agree with @The Planner for Bicester North to Aynho for both normal direction running and especially bi-di.

It's still not brilliant, it drops to 4 north of Risborough and 5 north of Bicester. Its 5 on the down if you have a stopper at Haddenham. If the SRFI at Ardley ever comes off, a slow freight out the terminal is going to chew capacity.

 

[cle]

What more would that signalling really unlock? The maximum I can recall was the 2tph Birmingham and 1tph Banbury/Stratford - which would fit today, no? Is there demand, or space further south for more?

I guess there was Wrexham/Shropshire a few times a day - so maybe another hourly path? Where to?

 

[YamYamDave]

W10 or 12 Gauge Clearance London to Banbury? It would surely be a useful bypass of the WCML now we have bi-mode and tri-mode traction.

 

[zwk500]

W10 or 12 Gauge Clearance London to Banbury? It would surely be a useful bypass of the WCML now we have bi-mode and tri-mode traction.

For which flows?

 

[Zomboid]

Heading towards London from Bicester, unless there's something I'm missing you could get to the GWML via Greenford at West Ealing (could go either direction from there as it's a triangle) or via Wembley to the Dudding Hill lines facing south. So actually quite a few possible destinations for freight. Though not much that doesn't already have a viable route, and I would guess that the capacity to use the Chiltern line for such trains is rather limited.

 

[The Planner]

W10 or 12 Gauge Clearance London to Banbury? It would surely be a useful bypass of the WCML now we have bi-mode and tri-mode traction.

They will run at W8. No way will the Chiltern get cleared for W10 or more.

== Doublepost prevention - post automatically merged: 12 Jun 2026 ==

What more would that signalling really unlock? The maximum I can recall was the 2tph Birmingham and 1tph Banbury/Stratford - which would fit today, no? Is there demand, or space further south for more?

I guess there was Wrexham/Shropshire a few times a day - so maybe another hourly path? Where to?

It would certainly help south of Bicester.

 

[zwk500]

Heading towards London from Bicester, unless there's something I'm missing you could get to the GWML via Greenford at West Ealing (could go either direction from there as it's a triangle) or via Wembley to the Dudding Hill lines facing south. So actually quite a few possible destinations for freight. Though not much that doesn't already have a viable route, and I would guess that the capacity to use the Chiltern line for such trains is rather limited.

The nearest intermodal terminals to Bicester are on the Nuneaton-Birmingham Line. which flows would switch to routing Nuneaton-Coventry-Leamington or Small Heath-Leamington vice Nuneaton-Rugby-Wembley?

If a freight presented to Neasden Jn facing south the only place it can go is back west on the GWML.
The Greenford route at least provides access to Wembley Yard or the North London Line but they're already basically full anyway, and it's going to be preferable to run on the entirely 4-track GWML between London and Didcot and use the regulating points that existing between Didcot and Banbury than to try and lock into a path that cannot be held once committed at Ruislip.

 

[AlexSJW]

Quite a lot of infrastructure needs to be installed before battery electric trains can run, so they need to start pretty quickly, or else there'll be a large fleet of new trains gathering dust in sidings, unable to be used.

I assume Marylebone itself will be wired, even if the tunnels aren't.

The great thing about battery trains is that little infrastructure needs installing. The range claimed for battery trains by train manufacturers is impressive.

 

[stevieinselby]

I'm not sure the Chiltern line counts as an "underserved commuter line" these days, Marylebone gets 11.8 million entries/exits a year and that demand is coming from somewhere

Only 2 of the top 20 destinations from Marylebone are within the M25. Chiltern is a popular regional service, but its local offering is not much cop. There's a school of thought that says that it needs better services to the Sudburys and the Ruislips because an hourly 2-car Networker is insufficient for a suburban service ... and there's another school of thought that says those areas are already well served by the Piccadilly and Central Lines, and there is nowhere near enough potential demand to merit extending 9-car Lizzie Line trains to them.

Would it be worthwhile running a 15-minute frequency Lizzie service to Gerrards Cross, Beaconsfield and High Wycombe (with some calls at Denham and other intermediate stations), and then running all services from beyond High Wycombe non-stop from there to Marylebone? Potentially, almost all traffic from those stations is to points between Marylebone and High Wycombe so very few passengers would lose through services, it could speed up journeys for longer-distance passengers on the Oxford route if they weren't stopping, as well as giving those commuter towns a more frequent service and a service beyond Marylebone, which is a poorly connected terminus (and especially if it went via Old Oak Common for HS2 connections). But is there enough potential there to justify the expense? That's a difficult question.

 

[cle]

Only 2 of the top 20 destinations from Marylebone are within the M25. Chiltern is a popular regional service, but its local offering is not much cop. There's a school of thought that says that it needs better services to the Sudburys and the Ruislips because an hourly 2-car Networker is insufficient for a suburban service ... and there's another school of thought that says those areas are already well served by the Piccadilly and Central Lines, and there is nowhere near enough potential demand to merit extending 9-car Lizzie Line trains to them.

Would it be worthwhile running a 15-minute frequency Lizzie service to Gerrards Cross, Beaconsfield and High Wycombe (with some calls at Denham and other intermediate stations), and then running all services from beyond High Wycombe non-stop from there to Marylebone? Potentially, almost all traffic from those stations is to points between Marylebone and High Wycombe so very few passengers would lose through services, it could speed up journeys for longer-distance passengers on the Oxford route if they weren't stopping, as well as giving those commuter towns a more frequent service and a service beyond Marylebone, which is a poorly connected terminus (and especially if it went via Old Oak Common for HS2 connections). But is there enough potential there to justify the expense? That's a difficult question.

The thing is, it would be a shuttle to a bay or two at OOC. So OOC-High Wycombe 4tph - change for Elizabeth line, GWML, HS2... something of a shuttle.

A through train I agree would be a game-changer, but I also don't think the traffic is there. Most people in those three main places (GC, Bcf, HW) are captive to the Chiltern route already if they work in Central London. I'm not sure what is suppressed - non rail users probably work elsewhere, like M4 Corridor locations. Maybe a few in Oxford...

But overall it's still an indrect journey. Although better onward options than Marylebone and it might end up being far quicker like for like.

I just don't know if it's worth it without a huge homebuilding programme. Hayes and Southall combined are practically as busy as the whole Chiltern route these days (much more than Marylebone certainly and I expect 75%+ journeys involve it) - those three 'main' stations on the Chiltern route barely total 5m.

 

[Dstock7080]

Linespeed and signalling improvements on the Met Line would be a nice to have too, though not essential for the current 2tph off-peak.

Isn’t that coming with the 4LM project Harrow-Amersham?

 

[CyrusWuff]

Isn’t that coming with the 4LM project Harrow-Amersham?

I was thinking more between Amersham and Aylesbury, which has long signal sections where the recontrol to Marylebone IECC essentially just replaced the semaphores with colour lights in the same place.

That said, linespeed South of Amersham is currently lower than it used to be too.

 

[squingo44]

The thing is, it would be a shuttle to a bay or two at OOC. So OOC-High Wycombe 4tph - change for Elizabeth line, GWML, HS2... something of a shuttle.

A through train I agree would be a game-changer, but I also don't think the traffic is there. Most people in those three main places (GC, Bcf, HW) are captive to the Chiltern route already if they work in Central London. I'm not sure what is suppressed - non rail users probably work elsewhere, like M4 Corridor locations. Maybe a few in Oxford...

But overall it's still an indrect journey. Although better onward options than Marylebone and it might end up being far quicker like for like.

I just don't know if it's worth it without a huge homebuilding programme. Hayes and Southall combined are practically as busy as the whole Chiltern route these days (much more than Marylebone certainly and I expect 75%+ journeys involve it) - those three 'main' stations on the Chiltern route barely total 5m.

If the Elizabeth line were extended to the inner Chiltern Line stations, they would instantly become targets for new housebuilding. Induced demand is a powerful force.

 

[WideRanger]

If the Elizabeth line were extended to the inner Chiltern Line stations, they would instantly become targets for new housebuilding. Induced demand is a powerful force.

Surely only if 1) the existing provision is not enough to induce demand, and 2) there is realistic physical scope to build more buildings.

 

[zwk500]

The great thing about battery trains is that little infrastructure needs installing. The range claimed for battery trains by train manufacturers is impressive.

You still need the power for charging to be available, and of course suitable infrastructure to charge from.
In Chiltern's case, there is currently only the LU electrification to charge from, on one line and requiring a non-standard system to collect from.
So introducing battery trains to Chiltern will still require significant infrastructure works.

And theres been a bit of a gap between range claimed and range realised, although I am hopeful thats a technology maturity issue that will be resolved.

 

[AlexSJW]

In Chiltern's case, there is currently only the LU electrification to charge from, on one line and requiring a non-standard system to collect from.
So introducing battery trains to Chiltern will still require significant infrastructure works.the open country can be battery

Charging infrastructure can be where hefty electricity cables actually are - in stations. Using batteries in the open countryside is where the installation gains are. Also though thee tunnels out of Marylebone.

The gains on batteries recently is phenomenal. Soon these gains will work their way into trains. I can see de-electrification hapening

 

[AlexSJW]

If the Elizabeth line were extended to the inner Chiltern Line stations, they would instantly become targets for new housebuilding. Induced demand is a powerful force.

Use land value capture to fund it.

 

[Mikey C]

Even just wiring up Marylebone will be a major project, one which will take years to do if they're starting from zero.

 

[cle]

If the Elizabeth line were extended to the inner Chiltern Line stations, they would instantly become targets for new housebuilding. Induced demand is a powerful force.

Except that we go full circle to NIMBY mania - good luck getting those of Beaconsfield and Gerrards Cross on board with mass housebuilding. Or developing all these golf courses...

High Wycombe has seen development. Bicester has happened regardless. Aylesbury is too far but again developing. I'm not sure where else you could.

 

[md2016]

Except that we go full circle to NIMBY mania - good luck getting those of Beaconsfield and Gerrards Cross on board with mass housebuilding. Or developing all these golf courses...

High Wycombe has seen development. Bicester has happened regardless. Aylesbury is too far but again developing. I'm not sure where else you could.

Most peak trains are already standing room only from Beaconsfield, and the government is pushing through a fair amount of additional housebuilding (Wilton Park, Beeches Park, London Road). It'll be in desperate need of capacity soon. Plenty already drive to Amersham/ Chalfont to the north, or Burnham/ Taplow to the south for cost/ flexibility and a guaranteed seat.

No idea if the business case is there (especially as nearly all the demand between Marylebone-High Wycombe comes from the three final stops), but if future capacity requires an Old Oak Common connection, some wires being added and new rolling stock, I could see why crossrail might seem like a simpler option.

 

[cle]

The other fact is that Chiltern have been ok running extremely short trains for a London commuter route. 5 or 6 max usually!

When the new batt/AC stock comes, if it is in multiples of 4... 8 car trains would blow their minds and see capacity met.

 

[Bletchleyite]

The other fact is that Chiltern have been ok running extremely short trains for a London commuter route. 5 or 6 max usually!

When the new batt/AC stock comes, if it is in multiples of 4... 8 car trains would blow their minds and see capacity met.

Don't forget that 6x24 is about the same as 8x20. And that a 5 car 730/2 has roughly the same number of seats as an 8 car 350 without significant comfort decrease (so 10.730 is like a 16 car - a veritable people eater!).

Though Chiltern do love a good 2 car at times.

 

[MarlowDonkey]

Only 2 of the top 20 destinations from Marylebone are within the M25. Chiltern is a popular regional service, but its local offering is not much cop. There's a school of thought that says that it needs better services to the Sudburys and the Ruislips because an hourly 2-car Networker is insufficient for a suburban service ... and there's another school of thought that says those areas are already well served by the Piccadilly and Central Lines, and there is nowhere near enough potential demand to merit extending 9-car Lizzie Line trains to them.

The Sudbury stations are on the line to Neasden and Marylebone which branches off the line to Old Oak Common at South Ruislip.

If there's anything at all, I doubt it would be any more than reinstatement of the "New North Main Line" from South Ruislip to Old Oak Common with Old Oak Common becoming an alternative terminus to Marylebone with connections to the Elizabeth Line.

 

[Zomboid]

Don't forget that 6x24 is about the same as 8x20. And that a 5 car 730/2 has roughly the same number of seats as an 8 car 350 without significant comfort decrease (so 10.730 is like a 16 car - a veritable people eater!).

Though Chiltern do love a good 2 car at times.

The longest they run are 8x23, though those aren't plentiful.
They have no business operating 2 cars though, 3 should be the minimum. Though that's not an infrastructure issue...

 

[zwk500]

Charging infrastructure can be where hefty electricity cables actually are - in stations. Using batteries in the open countryside is where the installation gains are. Also though thee tunnels out of Marylebone.

Stations are not necessarily near any 'hefty' electric cables. A simple station can be fed from the grid as a domestic supply. A busier station may have a bigger connection but still doubtful it'd be of any use for electric charging (unless you went through the 'trickle-charge a shore reservoir and dump' option, which has it's own downsides)

You also need time to charge.

The gains on batteries recently is phenomenal. Soon these gains will work their way into trains. I can see de-electrification hapening

For third rail, yes. I don't see any 25KV AC OLE being taken down, primarily because we don't really have enough of it as is. I can, however, see lines that should be electrified being skipped because of batteries (frustratingly).