Chiltern Mainline Upgrades post TPE Mk5As

[BerkshireRails]

Here is my ideas for Chiltern Mainline post Mk5As, feel free to suggest your ideas and improvements;

London Marylebone 8 platforms,
Four tracking from London Marylebone to High Wycombe, (paired by direction apart from the approach to London Marylebone in St John's Wood and Lord Tunnels and on tge approach to High Wycombe),
New extra platforms at West Hampstead on the slows,
Linespeed enhancements and electrifaction to enable 110-125mph,
Replacement of the 68s with a 125mph electric loco,
Princess Risborough to Aylesbury double tracking,
Class 165s, 168s & 196s replaced by Siemens Desrios,
Route converted to ETCS Level 2 apart from Met,
Met section either modified to allow third rail pick up or OLE and fourth rail on the fasts between Harrow and Amersham,

Proposed service Frequency enhancement

4tph High Wycombe to London (Stopper),
4tph Aylesbury Vale Parkway to London Marylebone via Met (Semi-Fast),
2tph Princess Risborough to Milton Keynes Central via Aylesbury Vale Parkway (Stopper),
2tph London Marylebone to Birmingham Moor Street (Fast),
1tph London Marylebone to Kidderminster (Fast),
1tph London Marylebone to Oxford (Fast),
2tph London Marylebone to Cowley (Semi-Fast)

 

[JonathanH]

London Marylebone 8 platforms,

How would that be achieved? I realise there is the wall siding, but would the platform widths be reduced to fit them in?

 

[The Planner]

None of that will happen in the next 30 years apart from some non-continuous electrification and the replacement of 165s and 168s.

 

[bramling]

Here is my ideas for Chiltern Mainline post Mk5As, feel free to suggest your ideas and improvements;

London Marylebone 8 platforms,
Four tracking from London Marylebone to High Wycombe, (paired by direction apart from the approach to London Marylebone in St John's Wood and Lord Tunnels and on tge approach to High Wycombe),
New extra platforms at West Hampstead on the slows,
Linespeed enhancements and electrifaction to enable 110-125mph,
Replacement of the 68s with a 125mph electric loco,
Princess Risborough to Aylesbury double tracking,
Class 165s, 168s & 196s replaced by Siemens Desrios,
Route converted to ETCS Level 2 apart from Met,
Met section either modified to allow third rail pick up or OLE and fourth rail on the fasts between Harrow and Amersham,

Proposed service Frequency enhancement

4tph High Wycombe to London (Stopper),
4tph Aylesbury Vale Parkway to London Marylebone via Met (Semi-Fast),
2tph Princess Risborough to Milton Keynes Central via Aylesbury Vale Parkway (Stopper),
2tph London Marylebone to Birmingham Moor Street (Fast),
1tph London Marylebone to Kidderminster (Fast),
1tph London Marylebone to Oxford (Fast),
2tph London Marylebone to Cowley (Semi-Fast)

Quite a list of things there, but hard to see how it would be justified when the London/Birmingham market has had massive expenditure in the form of HS2, and the London/Oxford market has had GWML electrification and an element of route modernisation with it.

I’d say benefit could be delivered rather more cheaply by
* completing GWML electrification to Oxford to allow 8 and 12 car Electrostar formations
* lengthening of Chiltern formations where required, achieved through more rolling stock and platform extensions where appropriate (and presumably some investment in stabling provision if required to support this).

Aside from this I’d support electrification of the Chiltern lines, but I have a feeling that’s not going to happen for the foreseeable future.

 

[Farigiraf]

2tph Princess Risborough to Milton Keynes Central via Aylesbury Vale Parkway (Stopper),

If possible, this service should start at High Wycombe as it would then provide an actual destination for passengers from MK, rather than just two services attached onto each other.

2tph London Marylebone to Birmingham Moor Street (Fast),
1tph London Marylebone to Kidderminster (Fast),

Rather than 3tph to Birmingham which (especially post-HS2) seems a bit overkill, 1 fast to Stourbridge/Kidderminster and 1 semifast to Moor Street could work. Then, if possible, route the third service to Stratford-upon-Avon instead, restoring a pre-COVID link from London. If hourly is possible, then of course make it hourly, alternatively it could be hourly to Banbury with 2-hourly extensions to Stratford. With it being a London to Stratford-upon-Avon via Bicester service, first class would be a good idea, as it would most likely be popular.

4tph High Wycombe to London (Stopper)

Again, 4tph at the likes of Denham Golf Club, Seer Green etc. might be overdoing it. If the (quite difficult to resolve) problem of 'what to do with the smaller suburban Chiltern mainline stations in London' is sorted out then something like 4tph to West Ruislip with 2 continuing to High Wycombe (complemented by a semifast to Aylesbury/Oxford* giving Gerrards Cross/Beaconsfield a faster London service) would be the most likely resolution. All of this is not really possible to do without four tracking which won't be easy in suburban London and I doubt will happen for a long time.

* This is assuming that the Oxford service remains a slower alternative to GWR, not competing with it, as Didcot-Oxford electrification and a frequent service to Paddington would make GWR the clear winner of that competition anyway.

 

[BerkshireRails]

How would that be achieved? I realise there is the wall siding, but would the platform widths be reduced to fit them in?

The extra platforms would be built on the BNP building and tower blocks on the west side of the station.

 

[brad465]

It was not that long ago that Project Evergreen took place, which made some significant line speed upgrades to 100mph, along with track and signal capacity improvements. I doubt more of this is going to happen anytime soon. Electrification is possible, however this will definitely not be done in full; I suspect doing the tunnel approaches into Marylebone will be too difficult to justify the cost (both financially and in disruption to services while erected). Marylebone platforms will probably be done to recharge in the station, followed by the busiest sections of the mainline beyond Wembley. If a rolling programme of electrification in England is achieved, I suspect it will follow on from the TPRU, so nothing earlier than that.

 

[FMerrymon]

The current plan is to increase capacity by running into old oak common for which passive provision is being made during the station's build.

There are proposals to reach MK/Northampton (https://eastwestrail.org.uk/wp-cont...he-Case-for-Northampton-to-Old-Oak-Common.pdf) and expected improvements to frequency of services north of Banbury.

 

[BerkshireRails]

If possible, this service should start at High Wycombe as it would then provide an actual destination for passengers from MK, rather than just two services attached onto each other.

The reason for starting at Princess Risborough is to use the Aylesbury facing bay platform.

Rather than 3tph to Birmingham which (especially post-HS2) seems a bit overkill, 1 fast to Stourbridge/Kidderminster and 1 semifast to Moor Street could work. Then, if possible, route the third service to Stratford-upon-Avon instead, restoring a pre-COVID link from London. If hourly is possible, then of course make it hourly, alternatively it could be hourly to Banbury with 2-hourly extensions to Stratford. With it being a London to Stratford-upon-Avon via Bicester service, first class would be a good idea, as it would most likely be popular.

That is another possibility.

Again, 4tph at the likes of Denham Golf Club, Seer Green etc. might be overdoing it. If the (quite difficult to resolve) problem of 'what to do with the smaller suburban Chiltern mainline stations in London' is sorted out then something like 4tph to West Ruislip with 2 continuing to High Wycombe (complemented by a semifast to Aylesbury/Oxford* giving Gerrards Cross/Beaconsfield a faster London service) would be the most likely resolution. All of this is not really possible to do without four tracking which won't be easy in suburban London and I doubt will happen for a long time.

* This is assuming that the Oxford service remains a slower alternative to GWR, not competing with it, as Didcot-Oxford electrification and a frequent service to Paddington would make GWR the clear winner of that competition anyway.

The 4tph to High Wycombe extends the old Gerrards Cross and West Ruislip services to simplify local services and allow better crowd management. Also, this provides a turn-up-and-go service, making it more attractive to use the trains, as you can already tap on and off with a bank card. A lot of the Southern Chiltern Mainline was four-tracked at some point, so it mostly puts back what was previously there, although costly, it does improve reliability as the local services no longer have to wait for an express to pass.

The Oxford (Fasts) would have intermediate stops of (maybe West Ruislip), High Wycombe, (maybe Princess Risborough), Bicester Village and Oxford Parkway. The Oxford (Fasts) would be to compete with the GWR Oxford (Fasts),

The Cowley services would run through Oxford station to serve the Southeastern part of Oxford.

It was not that long ago that Project Evergreen took place, which made some significant line speed upgrades to 100mph, along with track and signal capacity improvements. I doubt more of this is going to happen anytime soon. Electrification is possible, however this will definitely not be done in full; I suspect doing the tunnel approaches into Marylebone will be too difficult to justify the cost (both financially and in disruption to services while erected). Marylebone platforms will probably be done to recharge in the station, followed by the busiest sections of the mainline beyond Wembley. If a rolling programme of electrification in England is achieved, I suspect it will follow on from the TPRU, so nothing earlier than that.

It is building on some proposed work post project Evergreen.

Quite a list of things there, but hard to see how it would be justified when the London/Birmingham market has had massive expenditure in the form of HS2, and the London/Oxford market has had GWML electrification and an element of route modernisation with it.

I’d say benefit could be delivered rather more cheaply by
* completing GWML electrification to Oxford to allow 8 and 12 car Electrostar formations
* lengthening of Chiltern formations where required, achieved through more rolling stock and platform extensions where appropriate (and presumably some investment in stabling provision if required to support this).

Aside from this I’d support electrification of the Chiltern lines, but I have a feeling that’s not going to happen for the foreseeable future.

The upgrades are less about Oxford, but rather the whole Chilterns as a complete area. Does GWR even have enough 387s to do that in the first place as they have gotten rid of 18 units, 15 to Heathrow Express and 3 to Great Northern?

Chiltern already runs 9-car trains at some points in the day, so frequency upgrades and electrification are some of the few ways to improve capacity on the Chilterns.

The current plan is to increase capacity by running into old oak common for which passive provision is being made during the station's build.

There are proposals to reach MK/Northampton (https://eastwestrail.org.uk/wp-cont...he-Case-for-Northampton-to-Old-Oak-Common.pdf) and expected improvements to frequency of services north of Banbury.

It will only be a two-platform station to provide up to 4tph. That could be a valuable place to run the Milton Keynes services to.

 

[SynthD]

A lot of the Southern Chiltern Mainline was four-tracked at some point

Do you have maps of what it once was?

 

[The Planner]

The current plan is to increase capacity by running into old oak common for which passive provision is being made during the station's build.

There are proposals to reach MK/Northampton (https://eastwestrail.org.uk/wp-cont...he-Case-for-Northampton-to-Old-Oak-Common.pdf) and expected improvements to frequency of services north of Banbury.

That is EEH wanting that, that isn't necessarily the plan.

== Doublepost prevention - post automatically merged: 10 Aug 2025 ==

Do you have maps of what it once was?

It wasnt all 4 track. It was mainly station loops.

 

[BerkshireRails]

Do you have maps of what it once was?

Neasden Junction to Sudbury Hill Harrow, South to West Ruislip, Denham, Gerrards Cross, Beaconsfield, High Wycombe, Princess, Bicester North and Hatton to Birmingham Moor Street, were all at one time four tracked. They had planned to join up Denham to the South to West Ruislip quadrack section which was never finished, in the 1930s.

 

[172007]

Neasden Junction to Sudbury Hill Harrow, South to West Ruislip, Denham, Gerrards Cross, Beaconsfield, High Wycombe, Princess, Bicester North and Hatton to Birmingham Moor Street, were all at one time four tracked.

Wasn't Hatton to Moor Street, 4 track started about half a mile before Lapworth.

 

[BerkshireRails]

Wasn't Hatton to Moor Street, 4 track started about half a mile before Lapworth.

Very possibly it was.

 

[MatthewHutton]

The current plan is to increase capacity by running into old oak common for which passive provision is being made during the station's build.

There are proposals to reach MK/Northampton (https://eastwestrail.org.uk/wp-cont...he-Case-for-Northampton-to-Old-Oak-Common.pdf) and expected improvements to frequency of services north of Banbury.

Which is bad because OOC isn’t in central London and is only on one ”tube” line - albeit a very strong one - certainly it has bad bus/taxi/on foot access to central London.

Also reverse branching is typically bad really and leads to bad passenger numbers as you don’t know where to go to get the train - there has been ~0 uplift on the LIRR in New York with the reverse branch to Grand Central as well as Penn Station and Grand Central is at least well located.

Perhaps a 30 minute OOC-Gerrards Cross-Beaconsfield-High Wycombe-Saunderton*-Princes Risborough-Monks Risbourgh (1tph)-Little Kimble (1tph)-Aylesbury-Aylesbury Vale Parkway-Calvert (for HS2)-Winslow-Bletchley-MK service might be interesting and would provide Heathrow connectivity and HS2 connectivity in the south as well as linking the Buckinghamshire towns together.

* If you stop every 30 minutes at Saunderton it is probably politically viable to not run Marylebone service.

== Doublepost prevention - post automatically merged: 10 Aug 2025 ==

Four tracking from London Marylebone to High Wycombe, (paired by direction apart from the approach to London Marylebone in St John's Wood and Lord Tunnels and on tge approach to High Wycombe)

Four tracking between Gerrards Cross (inclusive) and the Whitehouse Tunnel (exclusive) would allow dynamic overtakes and wouldn’t be too expensive I don’t think.

You could do some four tracking on the other side of the M25 if needed as well.

 

[BerkshireRails]

Four tracking between Gerrards Cross (inclusive) and the Whitehouse Tunnel (exclusive) would allow dynamic overtakes and wouldn’t be too expensive I don’t think.

You could do some four tracking on the other side of the M25 if needed as well.

That could be like a Phase 1 so you get some benefits, and you slowly expand the quad tracking between London and High Wycombe would would have the through lines realigned and an additional Bay installed. I would try and realign High Wycombe to get 75mph.

 

[D365]

Why would the Chiltern routes be in any rush to change over to ERTMS before their Class 16x fleets are withdrawn? The existing signalling assets are not yet life expired.

 

[BerkshireRails]

Why would the Chiltern routes be in any rush to change over to ERTMS before their Class 16x fleets are withdrawn? The existing signalling assets are not yet life expired.

It was a requirement as part of the switch off of the Chiltern Automatic Train Protection.

 

[NCT]

There is some civilisation along the Chiltern Main Line but not that much. There aren't enough humans for the level of service proposed.

There was a thread not long ago discussing historic extent of 4-tracking between Ruislip and Wembley and if memory serves correctly the conclusion was 'not a lot'. There were only station loops and platforms have since been rebuilt (avoiding unstable embankments) making four-tracking restoration tricky. There aren't that many bodies in the Sudburys and those areas aren't earmarked for development. There is not going to be a business case for four-tracking.

Restoring the pre-Covid service quantum is realistic, and one should take the opportunity to standardise the timetable to Swiss or Dutch style. Beyond that, lengthen trains if demand warrants it and electrify (if the most economically advantageous solution involves batteries I have no problem with that).

To be on the safe side, stoppers will likely need to be limited to 2tph, overtaken at West Ruislip or South Ruislip. Modern electric rolling stock should help reduce the stopping penalty and avoid/minimise faster services having to be pathed out. It might be possible to operate 2tph semi-fasts to give Gerrards Cross and Beaconsfield 4tph. How many of these terminate at Wycombe or run through to Aylesbury would depend on termating capacity and single line capacity.

Then you have 4tph first-stop Wycombe, which would probably have to be in 2 flights at the London end rather than every 15 minutes, in order to create enough space for the stoppers. South/West Ruislip - Wycombe that's the issue. You might be able to do them 10/20 apart.

Of those 4tph, 2tph goes to Birmingham the other 2tph Oxford. I'm currently undecided about Princes Risborough and Haddenham and Thame Parkway:
- Both should have connectivity to both Bicester Village and Bicester Town
- Passengers should be able to travel between them (skip-stopping is very 'un-Swiss')
The 'easy' answer would be for all 4 to stop but that feels like overserving these small places, and puts too much penalty into journey times to Oxford and Banbury / Warwick.

I think the answer is that, in each of the Oxford and Birmingham pairs, one calls at both Princes Risborough and Haddenham, and the other runs fast. The ones that run fast then call at Islip or King's Sutton (plus some performance), so that both tph arrive at Oxford or Banbury (as close as possible to) exactly half hour apart so not to lose the ability for Oxford and Leamington Spa to be timed as Swiss-style 'takt' nodes with strict 30minute rhythms. This pattern suggests you want those services to be relatively flighted so intervals at Princes Risborough and Haddenham are no worse than 20/40 apart.

London - Stratford-upon-Avon trains may be provided on top of the basic 4tph pattern.

 

[The Planner]

It was a requirement as part of the switch off of the Chiltern Automatic Train Protection.

ETCS is a long way from happening on the Chilterns.

 

[philosopher]

Here is my ideas for Chiltern Mainline post Mk5As, feel free to suggest your ideas and improvements;

London Marylebone 8 platforms,
Four tracking from London Marylebone to High Wycombe, (paired by direction apart from the approach to London Marylebone in St John's Wood and Lord Tunnels and on tge approach to High Wycombe),
New extra platforms at West Hampstead on the slows,
Linespeed enhancements and electrifaction to enable 110-125mph,
Replacement of the 68s with a 125mph electric loco,
Princess Risborough to Aylesbury double tracking,
Class 165s, 168s & 196s replaced by Siemens Desrios,
Route converted to ETCS Level 2 apart from Met,
Met section either modified to allow third rail pick up or OLE and fourth rail on the fasts between Harrow and Amersham,

Proposed service Frequency enhancement

4tph High Wycombe to London (Stopper),
4tph Aylesbury Vale Parkway to London Marylebone via Met (Semi-Fast),
2tph Princess Risborough to Milton Keynes Central via Aylesbury Vale Parkway (Stopper),
2tph London Marylebone to Birmingham Moor Street (Fast),
1tph London Marylebone to Kidderminster (Fast),
1tph London Marylebone to Oxford (Fast),
2tph London Marylebone to Cowley (Semi-Fast)

This list of improvements I think would have made sense if HS2 were not being built as it would provide three trains per hour to Birmingham with journey times perhaps comparable to the current Avanti service, plus an alternative London to Milton Keynes route. Therefore it would have relieved the West Coast Mainline to a small extent. Since HS2 is being built to provide additional capacity, I just can’t see the need for a massive programme to increase capacity on the Chiltern Mainline.

With HS2, the only improvements in the next 10 to 20 years I can really see are some electrification and new rolling stock. I would expect frequencies to remain similar to what they are now, although there may be some train lengthening.

 

[MatthewHutton]

Of those 4tph, 2tph goes to Birmingham the other 2tph Oxford. I'm currently undecided about Princes Risborough and Haddenham and Thame Parkway

Do not forget Saunderton has to have some trains and Haddenham and Thame Parkway has roughly 50% more passengers than Princes Risborough (nearly 800k vs just over 500k including interchanges) - it actually has more passengers than Bicester North (750k) now.

In general that does support faster Oxford service as Bicester Village has 1.7 million passengers a year. It’s actually only a touch less than High Wycombe (1.9 million).

== Doublepost prevention - post automatically merged: 10 Aug 2025 ==

Since HS2 is being built to provide additional capacity, I just can’t see the need for a massive programme to increase capacity on the Chiltern Mainline.

The Chiltern lines are going to have to be high up the list for further improvements given the disruption being caused by the HS2 construction.

 

[NCT]

Do not forget Saunderton has to have some trains and Haddenham and Thame Parkway has roughly 50% more passengers than Princes Risborough (nearly 800k vs just over 500k including interchanges) - it actually has more passengers than Bicester North (750k) now.

In general that does support faster Oxford service as Bicester Village has 1.7 million passengers a year. It’s actually only a touch less than High Wycombe (1.9 million).

Haddenham is still in the 2tph territory, though 4tph might not be too ridiculous. As a P&R railhead I do see the attraction of 2tph to each of Oxford and Birmingham.

Saunderton just needs a welfare stop on the Aylesbury service.

 

[HamworthyGoods]

The extra platforms would be built on the BNP building and tower blocks on the west side of the station.

Wouldn’t that be quite challenging having some platforms at current level and some elevated on top of existing buildings?

 

[MatthewHutton]

Haddenham is still in the 2tph territory, though 4tph might not be too ridiculous. As a P&R railhead I do see the attraction of 2tph to each of Oxford and Birmingham.

Saunderton just needs a welfare stop on the Aylesbury service.

But if you want to do that reliably then the Aylesbury service needs to be extended to London (and be relatively fast - it can’t call at every station to London Marylebone I don’t think) - plus extra track is needed so at least a train length north of Princes Risborough it is double track to avoid delays cascading.

 

[NCT]

But if you want to do that reliably then the Aylesbury service needs to be extended to London (and be relatively fast - it can’t call at every station to London Marylebone I don’t think) - plus extra track is needed so at least a train length north of Princes Risborough it is double track to avoid delays cascading.

If the 2tph semifasts could be provided (on top of the 4tph fasts and 2tph stoppers) then it would make sense for the Aylesbury to be an extension of the semifasts.

 

[MatthewHutton]

If the 2tph semifasts could be provided (on top of the 4tph fasts and 2tph stoppers) then it would make sense for the Aylesbury to be an extension of the semifasts.

Agreed. OOC could be another destination for the Aylesbury semi-fasts I think.

 

[The Planner]

The Chiltern lines are going to have to be high up the list for further improvements given the disruption being caused by the HS2 construction.

Why? Chiltern itself hasn't been massively disrupted by it. The only interactions have been at West Ruislip and south of Wendover on the Met. You can't justify upgrades just because a separate project has inconvenienced potentially non rail users.

 

[BerkshireRails]

Wouldn’t that be quite challenging having some platforms at current level and some elevated on top of existing buildings?

The buildings mentioned would be demolished to create space for the tracks to be all at one level, then Oversite Development would take place at London Marylebone.

This list of improvements I think would have made sense if HS2 were not being built as it would provide three trains per hour to Birmingham with journey times perhaps comparable to the current Avanti service, plus an alternative London to Milton Keynes route. Therefore it would have relieved the West Coast Mainline to a small extent. Since HS2 is being built to provide additional capacity, I just can’t see the need for a massive programme to increase capacity on the Chiltern Mainline.

With HS2, the only improvements in the next 10 to 20 years I can really see are some electrification and new rolling stock. I would expect frequencies to remain similar to what they are now, although there may be some train lengthening.

Trains would be extended to be 5 cars off peak and 10 cars in the peak. HS2 might not provide enough capacity for all of the extra travellers, hence these upgrades.

There was a thread not long ago discussing historic extent of 4-tracking between Ruislip and Wembley and if memory serves correctly the conclusion was 'not a lot'. There were only station loops and platforms have since been rebuilt (avoiding unstable embankments) making four-tracking restoration tricky. There aren't that many bodies in the Sudburys and those areas aren't earmarked for development. There is not going to be a business case for four-tracking.

All there wasn't a lot restoring what was there and sorting out the platforms and earthworks, with a project to link up quad track sections and extend it into London Marylebone.

To be on the safe side, stoppers will likely need to be limited to 2tph, overtaken at West Ruislip or South Ruislip. Modern electric rolling stock should help reduce the stopping penalty and avoid/minimise faster services having to be pathed out. It might be possible to operate 2tph semi-fasts to give Gerrards Cross and Beaconsfield 4tph. How many of these terminate at Wycombe or run through to Aylesbury would depend on termating capacity and single line capacity.

Considering there is already 4tph stopper, formed from West Ruislip, Gerrards Cross and High Wycombe services, 2tph stopper will not cut it hence you require a 4tph stopper to High Wycombe.

Of those 4tph, 2tph goes to Birmingham the other 2tph Oxford. I'm currently undecided about Princes Risborough and Haddenham and Thame Parkway:

- Both should have connectivity to both Bicester Village and Bicester Town
- Passengers should be able to travel between them (skip-stopping is very 'un-Swiss')
The 'easy' answer would be for all 4 to stop but that feels like overserving these small places, and puts too much penalty into journey times to Oxford and Banbury / Warwick.
London - Stratford-upon-Avon trains may be provided on top of the basic 4tph pattern.

That could be a possible long distance services pattern however the Aylesbury services would run to Milton Keynes Central from Princess Risborough via Aylesbury to provide a direct link from Aylesbury and Southern Chiltern Mainline with the West Coast Mainline.

 

[MatthewHutton]

Why? Chiltern itself hasn't been massively disrupted by it. The only interactions have been at West Ruislip and south of Wendover on the Met.

And all the road disruptions and the extra construction traffic and making a whole swathe of countryside ugly while they are doing it.

You can't justify upgrades just because a separate project has inconvenienced potentially non rail users.

I mean you really really can. It’s not like they won’t also stand on their merits.

Also with the line initially terminating at Old Oak Common you probably need the goodwill/traffic from the Chilterns to boost the ridership to something reasonable.