Great Western Mainline Elizabeth Line upgrades

[BerkshireRails]

If there is likely to be any major further improvements to the GWML, it is much more likely to be a HS4 taking high speed services from London to South Wales/Devon and Cornwall/the West Country. Such a line would be better tunnelled out to south of Hayes, where it can follow the M4 towards the South West.
A tunnel for suburban services west of Paddington (or, more accurately, Royal Oak), can't be justified for the additional services that could possibly be operated based on feasible growth in passenger numbers.

Now, if you wanted extra capacity and more trains to Heathrow, a frequent suggestion and a much easier plan would be to either 1) extend Heathrow Express through to south/west of Heathrow using the proposed Southern/Western Access - in order to justify their presence on the GWML, based on average passengers through to central London from non-Heathrow destinations bolstering the passenger numbers or 2) replace Heathrow Express with Elizabeth Line services that also likely extend through to the Western/Southern access routes and increase capacity to attract more passengers in a similar way.

Heathrow Third runway plus increased development and Heathrow Southern Railway will increase demand, as it will become a more practical way of getting from the Southern Region to Western Region.

I think a Suburban tunnel for upto 26tph in the Peaks can be justified. The Crossrail Central Operating Section is designed for up to 32tph with 6tph being Reading services so the other 26tph could be for Hwathrow and beyond services. I would build a step plat junctions between Paddington and Westbourne Park to enable a grade separated junction. This would enable a new interchange station at Westbourne Park to be created. This would then allow the stopping patterns to be simplified. Into All Station for the tunnel and Semi Fast for the Reliefs, Ealing Broadway, West Ealing and Hayes & Harlington.

Converting Heathrow Express to a Through running Elizabeth Line services wouldn't be operationally a good idea because of flat junction at Ladbroke Grove. Which will limit capacity and operational reliability, which is already shown by the Didcot to London stoppers being cancelled when ever there is an issue on the Great Western Mainline because of there crossing move between the Reliefs and the Mains at Dolphin Junction.
Approach into London Paddington. In normal service, Heathrow Express and Great Western Railways use the Mains between Dolphin Junction and Ladbroke Grove Junction where they then switch to Lines 1-3. With Elizabeth Line using the Reliefs until Ladbroke Grove where it becomes lines 4-6.

 

[SynthD]

Old Oak Common and Westbourne Park and Paddington stops for differing interchange? It’s getting too complicated.

If you’re increasing the relief line services, why not send more towards Reading? Is it that Reading trains don’t appear full - but they are when in London, more West Drayton starters may be needed.

I imagine some of those 26tph you’re sending through Heathrow will go on the Western access, to the GWML. How many do you want to send to the SWML, what’s the passenger demand and track capacity you’re thinking of?

I think the general theory is good. Fast trains want a tunnel from near the terminus to near the city edge or the end of the stopper services. Stopping trains want a tunnel in the other direction, to go under the terminus, city centre and another terminus on the other side. Two portals close together, maybe in sight of each other. HS1 and Thameslink may be the only example of this in London.

 

[BerkshireRails]

Old Oak Common and Westbourne Park and Paddington stops for differing interchange? It’s getting too complicated.

Trying to speed up interchange for Hammersmith & City and Circle Lines and Elizabeth Line since you won't have to cross from North Western to South Eastern end of Paddington saving 5-10 minutes.

If you’re increasing the relief line services, why not send more towards Reading? Is it that Reading trains don’t appear full - but they are when in London, more West Drayton starters may be needed.

The GWR Didcot and Newbury stoppers would remain on the Reliefs from Reading to Paddington calling at Ealing Broadway, West Ealing, Hayes & Harlington, West Drayton, Slough, Maidenhead and Twyford in-between Reading and Paddington. This would provide an additional 3-4tph calling at West Drayton.

I imagine some of those 26tph you’re sending through Heathrow will go on the Western access, to the GWML. How many do you want to send to the SWML, what’s the passenger demand and track capacity you’re thinking of?

It would probably be something like 6tph to Heathrow T4 which would be double tracked, 6tph to Staines via Heathrow T5 and 6tph to Woking via Heathrow T5, 6tph to Heathrow T6 and 2tph to somewhere else.

 

[Railwaysceptic]

Old Oak Common and Westbourne Park and Paddington stops for differing interchange? It’s getting too complicated.

If you’re increasing the relief line services, why not send more towards Reading? Is it that Reading trains don’t appear full - but they are when in London, more West Drayton starters may be needed.

The Relief Lines between Reading and Acton Main Line are also an important freight route. Capacity for those trains cannot be handed over to extra Elizabeth Line trains.

 

[AlastairFraser]

Heathrow Third runway plus increased development and Heathrow Southern Railway will increase demand, as it will become a more practical way of getting from the Southern Region to Western Region.

Sorry, didn't see this thread.
Unfortunately, I don't think the Heathrow 3rd Runway will actually be built in its current form. The Heathrow Southern Railway, maybe, but only if an alternative way is found to increase Heathrow capacity.

The Crossrail Central Operating Section is designed for up to 32tph with 6tph being Reading services so the other 26tph could be for Hwathrow and beyond services.

Does Heathrow have the demand for 26tph an hour, even if you used the Western/Southern approaches to extend to Staines/Woking and/or Slough/Reading?

This would enable a new interchange station at Westbourne Park to be created

This is way too close to Paddington for a stop, Acton Main Line would be better if you really wanted an interchange (even with underground platforms).

Converting Heathrow Express to a Through running Elizabeth Line services wouldn't be operationally a good idea because of flat junction at Ladbroke Grove. Which will limit capacity and operational reliability, which is already shown by the Didcot to London stoppers being cancelled when ever there is an issue on the Great Western Mainline because of there crossing move between the Reliefs and the Mains at Dolphin Junction.

Why not try to grade separate either this junction or adjacent junctions instead? It would provide you with the extra paths from replacing Heathrow Express, at a fraction of the cost of a tunnel all the way out to Hillingdon.

If you’re increasing the relief line services, why not send more towards Reading? Is it that Reading trains don’t appear full - but they are when in London, more West Drayton starters may be needed.

To be honest, the Reading stoppers have a high enough frequency for the demand west of the M25, especially west of Slough. It's east of the M25 where more services could be useful - perhaps if the Western Rail Access was built, extending the existing T5 terminators to Maidenhead to soak up Slough/Maidenhead area passengers and leave capacity for more west London passengers would be wise.

Trying to speed up interchange for Hammersmith & City and Circle Lines and Elizabeth Line since you won't have to cross from North Western to South Eastern end of Paddington saving 5-10 minutes.

Much cheaper to build a dedicated link with travelator from Paddington Elizabeth Line to Paddington Hammersmith and City/Circle.

The GWR Didcot and Newbury stoppers would remain on the Reliefs from Reading to Paddington calling at Ealing Broadway, West Ealing, Hayes & Harlington, West Drayton, Slough, Maidenhead and Twyford in-between Reading and Paddington. This would provide an additional 3-4tph calling at West Drayton.

Why would you slow down these services like this?!

 

[BerkshireRails]

This is way too close to Paddington for a stop, Acton Main Line would be better if you really wanted an interchange (even with underground platforms).

Westbourne Park had mainline platforms up to 1993, they were only removed to enable a remodeling of the layout at Paddington and never put back. There was suggestions of putting them back as part of Crossrail and Old Oak Common.

Does Heathrow have the demand for 26tph an hour, even if you used the Western/Southern approaches to extend to Staines/Woking and/or Slough/Reading?

Heathrow does have the demand even from massive modal shift from road to rail for people living South West of Heathrow. It is arguably easier to get to Gatwick Airport by rail from Reading than Heathrow Airport.

Why not try to grade separate either this junction or adjacent junctions instead? It would provide you with the extra paths from replacing Heathrow Express, at a fraction of the cost of a tunnel all the way out to Hillingdon.

It might provide 2 paths, with the other 2 Heathrow Express might be taking up by the reduced speed of the 345s compared to the 387s. It would take a 345 approximately an extra 1 1/2 minutes to travel between Heathrow Airport Junction and Ladbroke Grove Junction non stop on the Mains, however it would logically call at Ealing Broadway and Old Oak Common which would add an extra 4 minutes on top of the 1 1/2 increase in journey time.

Much cheaper to build a dedicated link with travelator from Paddington Elizabeth Line to Paddington Hammersmith and City/Circle.

Why would you slow down these services like this?!

But would it really be much cheaper when you do benefits to cost ratio for adding in a station at Westbourne Park on the Elizabeth line versus adding in a travelator.

You are increasing direct connectivity, it would also allow for both Newbury stopper and Fast to run all of the way into Paddington rather than just the fast with the stopper terminating at Reading.

The Relief Lines between Reading and Acton Main Line are also an important freight route. Capacity for those trains cannot be handed over to extra Elizabeth Line trains.

The only logical way of increasing capacity is by building more tracks, underground between Westbourne Park and Airport Junction at least to remove the Heathrow services from the existing tracks, as that is 6 paths now freed up for other services on the Reliefs and you can reduce journey times as you no longer have to book the fasts to travel at the same speed as tge stoppers.

Sorry, didn't see this thread.
Unfortunately, I don't think the Heathrow 3rd Runway will actually be built in its current form. The Heathrow Southern Railway, maybe, but only if an alternative way is found to increase Heathrow capacity.

Does Heathrow have the demand for 26tph an hour, even if you used the Western/Southern approaches to extend to Staines/Woking and/or Slough/Reading?

26tph is the maximum you could run to Heathrow, in reality you would probably run 18tph of Elizabeth Line to Heathrow, which would still double capacity to Heathrow on Elizabeth Line and increase frequency to every 10 minutes from every 15-30 minutes. Which is as frequent as the tube is.

 

[Railwaysceptic]

The only logical way of increasing capacity is by building more tracks, underground between Westbourne Park and Airport Junction at least to remove the Heathrow services from the existing tracks, as that is 6 paths now freed up for other services on the Reliefs and you can reduce journey times as you no longer have to book the fasts to travel at the same speed as the stoppers.

That would be mega-expensive and will never be approved.

 

[London Trains]

Westbourne Park had mainline platforms up to 1993, they were only removed to enable a remodeling of the layout at Paddington and never put back. There was suggestions of putting them back as part of Crossrail and Old Oak Common.

Heathrow does have the demand even from massive modal shift from road to rail for people living South West of Heathrow. It is arguably easier to get to Gatwick Airport by rail from Reading than Heathrow Airport.

It might provide 2 paths, with the other 2 Heathrow Express might be taking up by the reduced speed of the 345s compared to the 387s. It would take a 345 approximately an extra 1 1/2 minutes to travel between Heathrow Airport Junction and Ladbroke Grove Junction non stop on the Mains, however it would logically call at Ealing Broadway and Old Oak Common which would add an extra 4 minutes on top of the 1 1/2 increase in journey time.

But would it really be much cheaper when you do benefits to cost ratio for adding in a station at Westbourne Park on the Elizabeth line versus adding in a travelator.

You are increasing direct connectivity, it would also allow for both Newbury stopper and Fast to run all of the way into Paddington rather than just the fast with the stopper terminating at Reading.

The only logical way of increasing capacity is by building more tracks, underground between Westbourne Park and Airport Junction at least to remove the Heathrow services from the existing tracks, as that is 6 paths now freed up for other services on the Reliefs and you can reduce journey times as you no longer have to book the fasts to travel at the same speed as tge stoppers.

Surely if you were adding an extra station between Paddington and OOC, it would be at Ladbroke Grove and not at Westbourne Park? Fitting a station in at Ladbroke Grove would also be easier.

I agree with the concept of a tunnel, but why would you build a tunnel for the stopping services when you could build the same tunnel for the fasts (and put semi-fast services on the GWML mains) and save billions not having to build 6 underground stations?

 

[BerkshireRails]

Surely if you were adding an extra station between Paddington and OOC, it would be at Ladbroke Grove and not at Westbourne Park? Fitting a station in at Ladbroke Grove would also be easier.

Ladbroke Grove and Westbourne Park look limited on space above ground hence easier to put it underground. Which would also allow line speed to be raised from 40 to 90mph. My idea would be to put Westbourne Park station on the country side of the A4207

I agree with the concept of a tunnel, but why would you build a tunnel for the stopping services when you could build the same tunnel for the fasts (and put semi-fast services on the GWML mains) and save billions not having to build 6 underground stations?

You would need to grade separate Ladbroke Grove or Portobello Junction as well as double up Stockley Bridge Junction. To remove crossing conflicts between Up Main and Down Relief Line services.


Plus the Paddington approach is already quite constrainted so hence I went for the extension of the Elizabeth Line core with step plate junctions which are fully underground, and the dive site on western end can be located in Stockley Bridge area which has a bit more space for dive site. I know it isn't standard practice but it made the most sense to me.

In my view the first place you could reasonable put a dive site for the Mains would be between Portobello Junction and Old Oak Common. Which wouldn't have a have impact on capacity compared to running Elizabeth stoppers underground to Hayes & Harlington.

 

[AlastairFraser]

Westbourne Park had mainline platforms up to 1993, they were only removed to enable a remodeling of the layout at Paddington and never put back. There was suggestions of putting them back as part of Crossrail and Old Oak Common.

The tube serves demand for the area completely adequately, so there's no real reason to rebuild them.

Heathrow does have the demand even from massive modal shift from road to rail for people living South West of Heathrow. It is arguably easier to get to Gatwick Airport by rail from Reading than Heathrow Airport.

Hants and Surrey sure, but that won't be served well by additional services into central London. That would be served by rail connections such as the Heathrow Southern Railway/Western Rail Access to Heathrow proposals.
And it is very easy to get to Heathrow from most Thames Valley towns. You have the Rail Air, the Elizabeth Line and back track at Hayes & Harlington combo, Flightline/The Airline buses, EL to West Drayton and quick bus to Heathrow T5, frequent National Express coaches etc..

The only place where the options are thin on the ground is further north in Herts or Beds, even then it's usually only 1 change.

It might provide 2 paths, with the other 2 Heathrow Express might be taking up by the reduced speed of the 345s compared to the 387s. It would take a 345 approximately an extra 1 1/2 minutes to travel between Heathrow Airport Junction and Ladbroke Grove Junction non stop on the Mains, however it would logically call at Ealing Broadway and Old Oak Common which would add an extra 4 minutes on top of the 1 1/2 increase in journey time.

Well, the solution may be to upgrade linespeeds closer to Paddington (perhaps as part of ETCS for that). I agree that a Old Oak Common stop would be needed (for GWR intercity users doubling back and HS2), but Ealing Broadway already has a frequent EL service with less than half an hour journey time to all terminals, it doesn't need a stop on the semi fast HeX replacer.

But would it really be much cheaper when you do benefits to cost ratio for adding in a station at Westbourne Park on the Elizabeth line versus adding in a travelator.

How are you increasing direct connectivity, when all the interchange opportunities and more are available at the station next door? A 5 min walk through a travelator or similar interchange walks to other lines is hardly an imposition.

it would also allow for both Newbury stopper and Fast to run all of the way into Paddington rather than just the fast with the stopper terminating at Reading.

Why on earth would you do this? It's much better and faster to interchange onto a 125mph capable IET at Reading, than waste an east of Reading path on a 110mph Class 387 that won't even be stopping to provide additional connectivity that way.

The only logical way of increasing capacity is by building more tracks, underground between Westbourne Park and Airport Junction at least to remove the Heathrow services from the existing tracks, as that is 6 paths now freed up for other services on the Reliefs and you can reduce journey times as you no longer have to book the fasts to travel at the same speed as tge stoppers.

Or you build an intercity tunnel that starts at Old Oak Common/OOC (after upgrading the Paddington - OOC section to a consistent 6 tracks, which is mostly there now) and surfaces near Osterley, where it parallels the M4 till Bristol eventually (first phase Reading, reconnect to the GWML via a west-facing spur from the high speed line up the A329(M) corridor, and, in later phases, a high speed spur joining the high speed line from the Berks and Hants line a few hundred meters east of Theale station.

This would be a much more long-lasting and value for money investment in increasing capacity, as not only can you finally have a long-mooted HSR stop directly serving Heathrow, but you can turn most of the GWML east of Reading into a suburban, freight and semi-fast intercity line only (potentially even some reopenings with through services from Paddington e.g. Bourne End - Marlow), and enable many more fast intercity services heading for the South West/Bristol/South Wales to run without significant conflicts with the suburban and regional services.

However, I think any new line along the GWR corridor will be a long while off due to the recent upgrades, the Midland Main Line and regional lines (especially the trans-Pennine corridors/lines like Bristol to Birmingham) will be a much priority for major upgrades.

Western Rail Access to Heathrow/Heathrow Southern Railway is the best we'll likely see before 2040, and those do provide massively significant boosts in connectivity on their own.

== Doublepost prevention - post automatically merged: 27 Aug 2025 ==

26tph is the maximum you could run to Heathrow, in reality you would probably run 18tph of Elizabeth Line to Heathrow, which would still double capacity to Heathrow on Elizabeth Line and increase frequency to every 10 minutes from every 15-30 minutes. Which is as frequent as the tube is.

Does Heathrow really need another tube level capacity line?
18tph Class 345s would carry up to 27,000 people an hour, that's 567,000 a day max capacity (given it operates for 21 hours a day).
Add current off peak Piccadilly line frequency at 12tph; with 1973 Stock capacity you can transport 8,208 an hour with 12tph. Scale that up to the 19 hour service day that the Picc seems to operate to Heathrow, that's 155,952 passenger capacity.
Add all the other transport modes and the fact that a lot of passengers are not coming from London.

Now, apparently Heathrow had 83,859,729 passengers last year.
That's around 229k a day.
Even when you consider just your proposed 18tph and the Tube, that's nearly 3 times current Heathrow daily passenger numbers in capacity, and, even if the 3rd runway is built, it isn't going to increase passenger numbers to 750k plus per day!

 

[BerkshireRails]

The tube serves demand for the area completely adequately, so there's no real reason to rebuild them.

That is debateable, as the tube train requires you to head East to head Down the Great Western Mainline which would no longer be required.

Hants and Surrey sure, but that won't be served well by additional services into central London. That would be served by rail connections such as the Heathrow Southern Railway/Western Rail Access to Heathrow proposals.
And it is very easy to get to Heathrow from most Thames Valley towns. You have the Rail Air, the Elizabeth Line and back track at Hayes & Harlington combo, Flightline/The Airline buses, EL to West Drayton and quick bus to Heathrow T5, frequent National Express coaches etc..

Heathrow Southern railway needs the extra paths, as some passengers will treat it as a through Line to central London, since even though it is all stops it would be around 15 minutes faster than the South Western Railway service. Taking 2U18 for example it takes 40 minutes to go from Staines to London Waterloo, then 15 minute interchange at London Waterloo, then 5 minutes to Tottenham Court Road so in total around 60 minutes, Elizabeth Line would be around 45 minutes Staines to Tottenham Court Road. Elizabeth Line is already booked timing wise between Paddington and Hayes & Harlington as if it calls at all Stations due to number of trains.

The only place where the options are thin on the ground is further north in Herts or Beds, even then it's usually only 1 change.

Well, the solution may be to upgrade linespeeds closer to Paddington (perhaps as part of ETCS for that). I agree that a Old Oak Common stop would be needed (for GWR intercity users doubling back and HS2), but Ealing Broadway already has a frequent EL service with less than half an hour journey time to all terminals, it doesn't need a stop on the semi fast HeX replacer.

I would disagree about not having Ealing Broadway as a station stop on the Semi-Fasts. As it is another major interchange for South West London. Old Oak Common will reduce line speed from 85/MU100 to 60.

How are you increasing direct connectivity, when all the interchange opportunities and more are available at the station next door? A 5 min walk through a travelator or similar interchange walks to other lines is hardly an imposition.

Why on earth would you do this? It's much better and faster to interchange onto a 125mph capable IET at Reading, than waste an east of Reading path on a 110mph Class 387 that won't even be stopping to provide additional connectivity that way.

The 387s will be stopping to provide additional connectivity. Reading to Paddington they will call at Twyford, Maidenhead, Slough, West Drayton, Hayes & Harlington, West Ealing at least overnight, Ealing Broadway and Acton Mainline.

Or you build an intercity tunnel that starts at Old Oak Common/OOC (after upgrading the Paddington - OOC section to a consistent 6 tracks, which is mostly there now) and surfaces near Osterley, where it parallels the M4 till Bristol eventually (first phase Reading, reconnect to the GWML via a west-facing spur from the high speed line up the A329(M) corridor, and, in later phases, a high speed spur joining the high speed line from the Berks and Hants line a few hundred meters east of Theale station.

You don't built high speed railways to deliberately following Motorways, due to the tighter curves and more frequent curves on Motorways. If you building a railway and it just so happens to follow a motorway that is fine. The A329(M) follows the North Downs Line between Winnersh Triangle and Reading and that is third rail and has a 70mph limit in that area. The A329(M) has some rather sharp bends in built up areas of around 500m, you would very lucky to get 65mph out of that alignment.

(Credit = London Reconnections)
Doesn't look like six tracks will be enough. Currently the lines are normally used as such Line 1 GWR IET ECS moves, Line 2 Down Main, Line 3 Up Main, Line 4 Down Relief, Line 5 Up Relief, Line 6 Crossrail ECS moves. Line 6 doesn't exist fully as part of Line 6 is now the CCOS (Crossrail Central Operating Section) Westbound Line.

This would be a much more long-lasting and value for money investment in increasing capacity, as not only can you finally have a long-mooted HSR stop directly serving Heathrow, but you can turn most of the GWML east of Reading into a suburban, freight and semi-fast intercity line only (potentially even some reopenings with through services from Paddington e.g. Bourne End - Marlow), and enable many more fast intercity services heading for the South West/Bristol/South Wales to run without significant conflicts with the suburban and regional services.

My idea would enable an extra 7-8 IET paths an hour which is the same number of extra paths your idea will allow. The through service from Paddington to Marlow was withdrawn because of how inefficient it is for capacity as Marlow can only fit a 2car Turbo or a 3 car 230. It is much better to run 8-12 car 387s & 345s into Paddington rather than a 2 car Turbo.

Line Name	Current Paths (Airport Jn to Paddington){Peak}	Future Paths (Airport Jn to Paddington){Peak}	Designed Capacity (Airport Jn to Paddington)	Capacity Change in Seats per Hour*/**
Mains	20 (4xHEX 387s, 4xGWR 387s, 12xGWR IETs)	20xGWR IETs	22	+1,624
Relief	20 (14xTfL Rail, 6xFreight)	16+2 (4xGWR 387s, 6xFreight, 6xTfl Rail)[2xSpare for ECS moves to Reading]	22	-1,856
Crossrail Western Operating Section (CWOS)	0	≤26xTfL Rail	32	+11,804
Total Capacity (Mains + Reliefs + CWOS)	40	66	76	+11,572

*8car 387s, 9car IETs, 9car 345s.
**Compared to Now

Unit Class	Seating Capacity[+ Standing Capacity]
387/1 4car	222 (Based on a 357)
IET 9car	647
345 9car	454[+1046 Standing]

However, I think any new line along the GWR corridor will be a long while off due to the recent upgrades, the Midland Main Line and regional lines (especially the trans-Pennine corridors/lines like Bristol to Birmingham) will be a much priority for major upgrades.

Trans Pennine Route is currently being upgraded to provide a step change in service pattern.

Western Rail Access to Heathrow/Heathrow Southern Railway is the best we'll likely see before 2040, and those do provide massively significant boosts in connectivity on their own.

Which require extra through trains to provide the need increase in capacity for that.

Does Heathrow really need another tube level capacity line?
18tph Class 345s would carry up to 27,000 people an hour, that's 567,000 a day max capacity (given it operates for 21 hours a day).
Add current off peak Piccadilly line frequency at 12tph; with 1973 Stock capacity you can transport 8,208 an hour with 12tph. Scale that up to the 19 hour service day that the Picc seems to operate to Heathrow, that's 155,952 passenger capacity.
Add all the other transport modes and the fact that a lot of passengers are not coming from London.

Now, apparently Heathrow had 83,859,729 passengers last year.
That's around 229k a day.
Even when you consider just your proposed 18tph and the Tube, that's nearly 3 times current Heathrow daily passenger numbers in capacity, and, even if the 3rd runway is built, it isn't going to increase passenger numbers to 750k plus per day!

My plan would use Heathrow Western Access and Heathrow Southern Railway to enable removal of certain RailAir Buse routes. It isn't just Heathrow would benefit, the local communities like Southall and Hanwell would benefit from being able to fit on the train, rather than being left behind. The Luggage takes up lets say half of the standing space. That means there is only space for 523 people standing, which reduces capacity down to 17,586 per hour and it only operates for 19 hours a day with the first Up service being at the 05:20 at Heathrow Central and the last being 00:11 at Heathrow Central. This takes the maximum capacity down to 334,134 Elizabeth Line passengers per day. During the off Peak frequency might drop to 4tph from 6tph. Which gives a minimum capacity of 222,756 per day. Lets say 25% of all passengers are traveling through Heathrow from Western Access/Southern Access to Central London. This cuts minimum capacity to 167,067 per day for Heathrow passengers and maximum capacity for Heathrow passengers of 250,600 per day.

 

[D365]

Question: is any of the above based on proposals that are realistically going to come to light in the next 40, 50, 60 years? Or is this just a ”My idea for” type of discussion.

 

[AlastairFraser]

That is debateable, as the tube train requires you to head East to head Down the Great Western Mainline which would no longer be required.

It's a 4 min ride plus walking time at Paddington. That's not worth spending tens of millions on an extra station to change.

Heathrow Southern railway needs the extra paths, as some passengers will treat it as a through Line to central London, since even though it is all stops it would be around 15 minutes faster than the South Western Railway service.

You can disincentivize this by including a premium fare to travel via Heathrow (similar to how any heavy rail service works now at Heathrow).

Taking 2U18 for example it takes 40 minutes to go from Staines to London Waterloo, then 15 minute interchange at London Waterloo, then 5 minutes to Tottenham Court Road so in total around 60 minutes

How on earth does it take 15 mins to change at Waterloo? 5-8 mins at worst.

I would disagree about not having Ealing Broadway as a station stop on the Semi-Fasts. As it is another major interchange for South West London

It is a major interchange that already has direct timely access to Heathrow.

Old Oak Common will reduce line speed from 85/MU100 to 60.

We need to increase line speed further in to compensate.

The 387s will be stopping to provide additional connectivity. Reading to Paddington they will call at Twyford, Maidenhead, Slough, West Drayton, Hayes & Harlington, West Ealing at least overnight, Ealing Broadway and Acton Mainline.

There's no real additional connectivity gained, it's a simple change onto an Elizabeth Line train or GWR Didcot Parkway stopper at Reading, and this gives you far more option than 1 or 2 Newbury stoppers would.

You don't built high speed railways to deliberately following Motorways

Tell the French that (and even look at HS1 - it spends a lot of time next to the A2/M2/M20 for a reason).

. The A329(M) follows the North Downs Line between Winnersh Triangle and Reading and that is third rail and has a 70mph limit in that area.

The NDL doesn't have a low speed limit because it is curvy, it has it because there is no point having a higher speed limit (because of the stopping pattern of NDL/SWR Reading line trains and the limitations of 3rd rail technology).
A high speed rail on a viaduct on top of the A329M would mostly have a linespeed of 100mph+ until the last half a mile where it would slow down to join the GWML, near Thames Valley Park.

The A329(M) has some rather sharp bends in built up areas of around 500m, you would very lucky to get 65mph out of that alignment

Not at all, many mainlines have linespeeds of 100mph+ with curves sharper than that.

Doesn't look like six tracks will be enough. Currently the lines are normally used as such Line 1 GWR IET ECS moves, Line 2 Down Main, Line 3 Up Main, Line 4 Down Relief, Line 5 Up Relief, Line 6 Crossrail ECS moves. Line 6 doesn't exist fully as part of Line 6 is now the CCOS (Crossrail Central Operating Section) Westbound Line.

Line 1/Line 6 don't have to exclusively be used for ECS moves - especially as the replacement HeX trains would be extensions of Paddington Elizabeth Line terminators in many cases.

My idea would enable an extra 7-8 IET paths an hour which is the same number of extra paths your idea will allow.

7-8 IET paths for billions upon billions of tunneling for a suburban tunnel out to Hayes?!

The through service from Paddington to Marlow was withdrawn because of how inefficient it is for capacity as Marlow can only fit a 2car Turbo or a 3 car 230. It is much better to run 8-12 car 387s & 345s into Paddington rather than a 2 car Turbo.

I was suggesting operating a through service to High Wycombe via Bourne End and Loudwater on the former alignment, Marlow would become a shuttle.
I agree a 2 car turbo would be inefficient use of capacity - I'd use a 8 car Class 387 with ASDO on the smaller stations, some of which can't be practically upgraded (e.g. Cookham).

Trans Pennine Route is currently being upgraded to provide a step change in service pattern.

It is, but NPR is still needed to encourage greater modal shift in a combined region of over 13 million people, where it is also desperately necessary to kickstart regeneration for some towns.

Which require extra through trains to provide the need increase in capacity for that

Extra through trains that can be delivered by replacing the under utilised Heathrow Express and extending the insane number of Elizabeth Line services that currently have to turn back at Paddington.

My plan would use Heathrow Western Access and Heathrow Southern Railway to enable removal of certain RailAir Buse routes.

There will still be a certain demand for RailAir on the Reading/Woking routes, especially given the railway doesn't operate at some times that people need to access Heathrow and RailAir does, or go to places that don't have direct rail services to Heathrow/better located for a drop off from residential areas than a local station - e.g. Winnersh Triangle Park and Ride or the Bishops Centre in Taplow pickup.

It isn't just Heathrow would benefit, the local communities like Southall and Hanwell would benefit from being able to fit on the train, rather than being left behind.

Exactly why you extend existing EL trains to fill this purpose, instead of continue running comparatively utilised Heathrow Express trains.

The Luggage takes up lets say half of the standing space.

Unrealistic, people don't bring that much luggage with most airlines' policies towards bringing more than 2 23kg suitcases, even with business and first class passengers.

During the off Peak frequency might drop to 4tph from 6tph

The off-peak frequency is already minimum 6tph and will only increase.

Lets say 25% of all passengers are traveling through Heathrow from Western Access/Southern Access to Central London.

You'd price it to disincentivize these journeys to central London via Heathrow, as suggested above.

This cuts minimum capacity to 167,067 per day for Heathrow passengers and maximum capacity for Heathrow passengers of 250,600 per day.

As I mentioned before, Heathrow currently has an average passenger volume of around 229-230k a day. Around 11.6k on average a day are domestic, most of who will be connecting and never leave Heathrow.
Then you have to calculate that many Heathrow passengers are coming from elsewhere in the UK by car or coach and will not interact with the rail system either.
250k a day capacity on the Elizabeth Line + the nearly 156k daily Picc Line capacity will continue to serve Heathrow's central London rail transport needs well for generations.

I do admire your optimism and your research is good, but the inner GWML corridor has recently received a massive investment and upgrade.
A further large investment anytime soon is unlikely.
Why not focus that energy on designing and proposing rail schemes elsewhere, where the current service offering is very poor?

Question: is any of the above based on proposals that are realistically going to come to light in the next 40, 50, 60 years? Or is this just a ”My idea for” type of discussion.

I think my idea to get rid of HeX at some point and potentially replace with extended Elizabeth line services onto the Heathrow Southern Railway proposed alignment/diverted GWR regional & intercity services via the Western Rail Access to Heathrow is a proposal at least partially already being considered somewhere.
@Bald Rick @The Planner
Any ideas? I think I have seen discussion of the replacement of HeX on this forum by either of you at some point?

 

[BerkshireRails]

It's a 4 min ride plus walking time at Paddington. That's not worth spending tens of millions on an extra station to change.

That depends on price per minute.

You can disincentivize this by including a premium fare to travel via Heathrow (similar to how any heavy rail service works now at Heathrow).

That doesn't always work.

How on earth does it take 15 mins to change at Waterloo? 5-8 mins at worst.

National Rail Minimum Connection time says it takes 15 minutes as it is London Terminus

It is a major interchange that already has direct timely access to Heathrow.

It isn't just Heathrow it is also for the Tube.

We need to increase line speed further in to compensate.

You don't need to go fast, you just don't want to go slow.

There's no real additional connectivity gained, it's a simple change onto an Elizabeth Line train or GWR Didcot Parkway stopper at Reading, and this gives you far more option than 1 or 2 Newbury stoppers would.

Both Newbury and Didcot would follow the same calling pattern therefore giving 4tph GWR.

Tell the French that (and even look at HS1 - it spends a lot of time next to the A2/M2/M20 for a reason).

Even when does spend time next to the major road it doesn't follow every twist and turn.

The NDL doesn't have a low speed limit because it is curvy, it has it because there is no point having a higher speed limit (because of the stopping pattern of NDL/SWR Reading line trains and the limitations of 3rd rail technology).
A high speed rail on a viaduct on top of the A329M would mostly have a linespeed of 100mph+ until the last half a mile where it would slow down to join the GWML, near Thames Valley Park.

Not at all, many mainlines have linespeeds of 100mph+ with curves sharper than that.

The curve at Morpeth has a similar radius to the curve you would have at the A329(M) & M4 and that has a 50mph limit with 150mm of cant which is the maximum amount of cant allowed. I never said the North Downs in Winnersh area was limited due to the curvature. Which mainlines which have a higher top speed and a sharper bend?

Line 1/Line 6 don't have to exclusively be used for ECS moves - especially as the replacement HeX trains would be extensions of Paddington Elizabeth Line terminators in many cases.

Line1 & Line 6 do get used for other stuff like passing passenger trains to let an IET get in front of 387. That doesn't help with the lack of grade separation of the junctions on approach into Paddington, which would be required for 20-22tph on the Mains.

7-8 IET paths for billions upon billions of tunneling for a suburban tunnel out to Hayes?!

It is 7-8 IET Paths on top of the up to 26 extra Suburban paths.

I was suggesting operating a through service to High Wycombe via Bourne End and Loudwater on the former alignment, Marlow would become a shuttle.
I agree a 2 car turbo would be inefficient use of capacity - I'd use a 8 car Class 387 with ASDO on the smaller stations, some of which can't be practically upgraded (e.g. Cookham).

An 8 car 387 is over doing it, a 4 car will be long enough.

Extra through trains that can be delivered by replacing the under utilised Heathrow Express and extending the insane number of Elizabeth Line services that currently have to turn back at Paddington.

That requires grade separation and you might not get as many as you would think.

There will still be a certain demand for RailAir on the Reading/Woking routes, especially given the railway doesn't operate at some times that people need to access Heathrow and RailAir does, or go to places that don't have direct rail services to Heathrow/better located for a drop off from residential areas than a local station - e.g. Winnersh Triangle Park and Ride or the Bishops Centre in Taplow pickup.

However RailAir would operate mainly on a Weekend night rather than all day.

Unrealistic, people don't bring that much luggage with most airlines' policies towards bringing more than 2 23kg suitcases, even with business and first class passengers.

A 23kg suitcase takes up roughly the same base size and as someone standing, so I would argue it is realistic.

The off-peak frequency is already minimum 6tph and will only increase.

6tph isn't enough, plus what doesn't help is the calling pattern changes between trains which causes confusion. Hence my idea would be to simplify the service pattern into Mains (Express), Relief (Semi-fast) and CWOS (All Stations).

As I mentioned before, Heathrow currently has an average passenger volume of around 229-230k a day. Around 11.6k on average a day are domestic, most of who will be connecting and never leave Heathrow.
Then you have to calculate that many Heathrow passengers are coming from elsewhere in the UK by car or coach and will not interact with the rail system either.
250k a day capacity on the Elizabeth Line + the nearly 156k daily Picc Line capacity will continue to serve Heathrow's central London rail transport needs well for generations.

Not all of that Piccadilly Line and Elizabeth Line capacity is used by Heathrow the rest is used by other local communities, hence although it looks like an excessive capacity for Heathrow but once you factor in all other communities it becomes a decent capacity.

Why not focus that energy on designing and proposing rail schemes elsewhere, where the current service offering is very poor?

Because Elizabeth Line is Britain's busiest railway, in just 3 years of operation so it needs major upgrades to enable to maintain it rapid growth.

I think my idea to get rid of HeX at some point and potentially replace with extended Elizabeth line services onto the Heathrow Southern Railway proposed alignment/diverted GWR regional & intercity services via the Western Rail Access to Heathrow is a proposal at least partially already being considered somewhere.
@Bald Rick @The Planner
Any ideas? I think I have seen discussion of the replacement of HeX on this forum by either of you at some point?

My idea also gets rid of HEX.

Question: is any of the above based on proposals that are realistically going to come to light in the next 40, 50, 60 years? Or is this just a ”My idea for” type of discussion.

Maybe within the next 10-20 years, but probably more like 30-40 years.

 

[Railwaysceptic]

. . . . . Elizabeth Line is Britain's busiest railway, in just 3 years of operation so it needs major upgrades to enable to maintain it rapid growth.

The Elizabeth Line does not need major upgrades. The core platforms were constructed to allow longer trains as and when necessary, and selective door operation can be used for other stations with short platforms.

 

[BerkshireRails]

The Elizabeth Line does not need major upgrades. The core platforms were constructed to allow longer trains as and when necessary, and selective door operation can be used for other stations with short platforms.

The core is but the branches are unable to accommodate 11 car 345s, Heathrow, Hayes & Harlington bay, Chadwell Heath turnback, are just some of the limiting factors on length. London Reconnections article

 

[D365]

Why does Elizabeth Line need to ”maintain growth”? Like all other railways it will, at some point, reach saturation.

This strikes me as an exercise in diminishing returns.

 

[Snow1964]

The Relief Lines between Reading and Acton Main Line are also an important freight route. Capacity for those trains cannot be handed over to extra Elizabeth Line trains.

It is likely the freight could be handled on one reversible line. But widening the line is unlikely to be practical.

It is probably much easier to build new reversible flyover, (or dive under) between Hayes and Harrington and Slough, redirect the freight trains to Brentford (a former double line, now single, so space for long passing loop), reinstate a bridge over A4 (where old Firestone bridge was removed), a single line reversible spur towards Brentford station, after Brentford there was previously sidings, so already spare trackbed, leading to line to Acton (and onwards towards Willesden or Cricklewood area).

Most of this alternative route has 4 or less trains per hour, considerably less than 12-20tph each pair on GW line. Would be about 1km of brand new single track reversible link lines and about another 2km of track relaid on former trackbed. A tiny fraction of cost of trying to widen line through Hanwell and Ealing.

 

[BerkshireRails]

It is likely the freight could be handled on one reversible line. But widening the line is unlikely to be practical.

There is 6 paths of freight each way per hour. A single line will struggle with that amount of freight.

It is probably much easier to build new reversible flyover, (or dive under) between Hayes and Harrington and Slough, redirect the freight trains to Brentford (a former double line, now single, so space for long passing loop), reinstate a bridge over A4 (where old Firestone bridge was removed), a single line reversible spur towards Brentford station, after Brentford there was previously sidings, so already spare trackbed, leading to line to Acton (and onwards towards Willesden or Cricklewood area).

You will still have to send some stuff via the Reliefs to get to Hanwell bridge loop, Acton yard and a few other places.

Most of this alternative route has 4 or less trains per hour, considerably less than 12-20tph each pair on GW line. Would be about 1km of brand new single track reversible link lines and about another 2km of track relaid on former trackbed. A tiny fraction of cost of trying to widen line through Hanwell and Ealing.

The West London Orbital plans will increase number of trains to 12-16tph passenger wise, so trying to divert the 6tph GWML freight on top of North London Line freights just will not work reliability.

 

[Bald Rick]

Question: is any of the above based on proposals that are realistically going to come to light in the next 40, 50, 60 years? Or is this just a ”My idea for” type of discussion.

No, not remotely. Yes it is a “My (fantastical) idea for…”

But would it really be much cheaper when you do benefits to cost ratio for adding in a station at Westbourne Park on the Elizabeth line versus adding in a travelator.

Yes. A new Crossrail Style underground station is £1bn plus. A new at grade station at Westbourne Park would be, conservatively, £400m.

A new travelator in the Bakerloo link - perhaps £10m.

Does Heathrow really need another tube level capacity line?
18tph Class 345s would carry up to 27,000 people an hour, that's 567,000 a day max capacity (given it operates for 21 hours a day).
Add current off peak Piccadilly line frequency at 12tph; with 1973 Stock capacity you can transport 8,208 an hour with 12tph. Scale that up to the 19 hour service day that the Picc seems to operate to Heathrow, that's 155,952 passenger capacity.
Add all the other transport modes and the fact that a lot of passengers are not coming from London.

Now, apparently Heathrow had 83,859,729 passengers last year.
That's around 229k a day.
Even when you consider just your proposed 18tph and the Tube, that's nearly 3 times current Heathrow daily passenger numbers in capacity, and, even if the 3rd runway is built, it isn't going to increase passenger numbers to 750k plus per day!

I think you have calcuated the rail capacity one way, but the airport passenger numbers are both ways and include people who never leave the airport due to changing planes (about 20%). The number of air passengers travelling to (or from) the airport is around 30m a year, or about 80,000 a day. Even if they were all using rail, they would all fit on the Elizabeth line service alone, wihout need for HEx or the Piccadilly line.

Heathrow Southern railway needs the extra paths, as some passengers will treat it as a through Line to central London, since even though it is all stops it would be around 15 minutes faster than the South Western Railway service. Taking 2U18 for example it takes 40 minutes to go from Staines to London Waterloo, then 15 minute interchange at London Waterloo, then 5 minutes to Tottenham Court Road so in total around 60 minutes,

Taking 2U18 for example, it takes 36 from Staines to Vauxhall then a 5 minute (max) change on to the Victoria Line, arriving Oxford Circus 6 minutes later, so in total 47 minutes.

I think my idea to get rid of HeX at some point and potentially replace with extended Elizabeth line services onto the Heathrow Southern Railway proposed alignment/diverted GWR regional & intercity services via the Western Rail Access to Heathrow is a proposal at least partially already being considered somewhere.
@Bald Rick @The Planner
Any ideas? I think I have seen discussion of the replacement of HeX on this forum by either of you at some point?

If the Southern Link happens (the version towards Woking) it will be HEX extensions.

If the Western Link happens it will be Elizabeth Line extensions.

In theory they could be swapped.

GWR intercity servcies would never be routed that way.

 

[Railwaysceptic]

The core is but the branches are unable to accommodate 11 car 345s, Heathrow, Hayes & Harlington bay, Chadwell Heath turnback, are just some of the limiting factors on length. London Reconnections article

Hence: selective door operation.

 

[BerkshireRails]

Hence: selective door operation.

Selective Door Operation is no help when your fowling the crossovers at Heathrow, which would reduce capacity down to 2tph from 4tph.

 

[Bald Rick]

Selective Door Operation is no help when your fowling the crossovers at Heathrow, which would reduce capacity down to 2tph from 4tph.

Why would you fowl the crossovers? Wouldn’t the Elizabeth Line services just have the platfrom market board beyond the orth end of the London Bound platform at Central? Or would they chicken out?

 

[BerkshireRails]

Why would you fowl the crossovers? Wouldn’t the Elizabeth Line services just have the platfrom market board beyond the orth end of the London Bound platform at Central? Or would they chicken out?

The full Heathrow Branch is bi-directional. My concern is more to do with Heathrow T4 because of the single line. However you would need some way of getting the GPS based ASDO system not to release certain doors at underground stations.

Taking 2U18 for example, it takes 36 from Staines to Vauxhall then a 5 minute (max) change on to the Victoria Line, arriving Oxford Circus 6 minutes later, so in total 47 minutes.

If it only takes 5 minutes then why does TfL say it will take 9 minutes?
(Using Clapham Junction as it is the first stop after Vauxhall with Main Line services, Queenstown Road Battersea only get Windsor Line services and Pimlico is the first station heading north after Vauxhall).

If the Southern Link happens (the version towards Woking) it will be HEX extensions.

If the Western Link happens it will be Elizabeth Line extensions.

In theory they could be swapped.

GWR intercity servcies would never be routed that way.

In some marketing info for Western link Heathrow Express would have extended to Swindon and Newbury, with calls at Reading and Didcot Parkway.

Considering GWR operate HEX on behalf of Heathrow Airport I would imagine the GWR IET Crewe's would sign Heathrow encase something happens on the mainline to allow services to keep on moving.

Yes. A new Crossrail Style underground station is £1bn plus. A new at grade station at Westbourne Park would be, conservatively, £400m.

A new travelator in the Bakerloo link - perhaps £10m.

I ruled out new surface platforms due to lack of space.

 

[Class15]

If it only takes 5 minutes then why does TfL say it will take 9 minutes? View attachment 187475
(Using Clapham Junction as it is the first stop after Vauxhall with Main Line services, Queenstown Road Battersea only get Windsor Line services and Pimlico is the first station heading north after Vauxhall).

I can say very confidently from experience that @Bald Rick is correct and it doesn’t take anywhere near 9 minutes.

== Doublepost prevention - post automatically merged: 30 Aug 2025 ==

Yes. A new Crossrail Style underground station is £1bn plus. A new at grade station at Westbourne Park would be, conservatively, £400m.

Wow, these prices really are eye-watering. Really shows how much infrastructure costs!

 

[D365]

The full Heathrow Branch is bi-directional. My concern is more to do with Heathrow T4 because of the single line. However you would need some way of getting the GPS based ASDO system not to release certain doors at underground stations.

The Class 345s already have non-GPS based door control systems. Each train measures the rotation of the leading axles which are unmotored and unbraked.

 

[BerkshireRails]

The Class 345s already have non-GPS based door control systems. Each train measures the rotation of the leading axles which are unmotored and unbraked.

The Automatic Selective Door Opening (ASDO) system on our trains will release the doors based on the shortest platform at each station. Some platforms may be long enough to accommodate the train, but some doors may still not open. The system utilises a Global Positioning System (GPS) which is able to confirm where the train is but is not accurate enough to correctly identify the platform number. Therefore, where we have short platforms or large steps between train and platform (such as Paddington due to curvature) certain doors will not open, but this is applied for all platforms at that station.

No reference is made to that in this Freedom of Infomation request to TfL via What do they know website about the class 345 ASDO system.

 

[D365]

No reference is made to that in this Freedom of Infomation request to TfL via What do they know website about the class 345 ASDO system.

ASDO isn’t currently required in underground stations due to platforms being long enough for 9 car trains. My point is that the TCMS software could be updated if longer trains were ever required.

 

[Bald Rick]

If it only takes 5 minutes then why does TfL say it will take 9 minutes?

Presumably to allow for people of all abilities to make the advertised change.

Personally, I’ve done it in 90 seconds train to train.

In some marketing info for Western link Heathrow Express would have extended to Swindon and Newbury, with calls at Reading and Didcot Parkway.

Don’t beleive everything you read.

Considering GWR operate HEX on behalf of Heathrow Airport I would imagine the GWR IET Crewe's would sign Heathrow encase something happens on the mainline to allow services to keep on moving.

I would imagine they wouldn’t. Not least because they would then need to be ETCS trained.

 

[BerkshireRails]

I would imagine they wouldn’t. Not least because they would then need to be ETCS trained.

Which some of the links would be from driving the HEX 387s. Plus the ETCS is to replace the GWML ATP system which the IETs have.

Presumably to allow for people of all abilities to make the advertised change.

Personally, I’ve done it in 90 seconds train to train.

Then we should use the minimum connection TfL gives to be on the safe side. Although I have been known to make 2 minute connection at Reading from platform 2 to platform 14, I wouldn't plan my jounrey time around it, instead I would use the minimum connection time of 7 minutes.

Don’t beleive everything you read.

I was just adding that Heathrow Express had suggested they would extended to Newbury and Swindon, I know it is quite unlikely as Heathrow Expresses contract expires in 2028.