HS3 Paddington to Newport

[AlastairFraser]

I know it’s too early for it but how could a potential HS3 to the West look like. Currently the Great Western Mainline is at capacity between Reading and Paddington mainly because of the Elizabeth Line is hopefully this new line could divert existing GWR trains on the new line.

My vision would look like Paddington - Old Oak Common - Heathrow Central - Reading - New Bristol Cental Station? - Newport.

To cross the river Severn we will need to build a tunnel between Portishead and somewhere near the coast of Newport.

The most realistic way this would be built is by starting with Phase 1 between Paddington and Reading just to help alleviate capacity. Then Phase 2 between Newport and Bristol then Phase 3 between Reading and Bristol.

Benefits of HS3:

- Possibility to send GWR trains between Paddington and South Wales via Bristol which is a high demand destination.

- More capacity on the GWML so possibility to run additional Elizabeth Line trains, freight trains and even some more semi fast trains.

- Direct train connections between West England, South Wales and Heathrow Airport.

I think going the whole way into Paddington would be too expensive, given Central London land values and the experience of tunneling into Euston with HS2.
The removal of GWR long distance services would permit extension of more Elizabeth Line services west from Paddington anyway, to carry the passenger load into central London.

I'm going to structure this in stages, to make this easier to read (the HSR London to Wales is referred to as HS5, it is 4 track as far as eastern Bristol, then 2 tracks into Bristol and 2 tracks westwards into Wales).

Stage 1: I'd build a large 6 platform terminus for the HS5 line at Old Oak Common, but on the current Cargiant site off Hythe Road.
Then I'd link it using a people mover to Old Oak Common HS2/Elizabeth Line/Heathrow Express Station and Willesden Junction for orbital connections around London.

Maybe a connection to North Acton for the Central Line too.

Stage 2: Then I'd build a tunnel from the HS5 Old Oak Common station to a tunnel portal by the M4 west of B454 Windmill Lane in Osterley.
Follow the M4 on a elevated viaduct as far as Heston services, then a tunnel towards a Heathrow station under Heathrow Terminal 3 (likely due for redevelopment by the time this is proposed).

Stage 3:  
Continued tunnel from Heathrow T3 HS5 station to the southbound M4 carriageway, west of Junction 5 for Slough East and Colnbrook.
Resumption of an elevated viaduct following the motorway as far as the M48/M4 split north of Bristol. (Yes, I know this is a long section, but this makes sense to minimise the land take of the railway within an existing transport corridor, as much as possible.)

Stage 4:
A new 2 track Severn tunnel from west of the M48/M4 split to west of Magor. 2 dedicated tracks alongside the South Wales Main Line/SWML until the outskirts of Newport (perhaps using the disused tracks south of the SWML). Either a junction with the SWML here only, or, if extra funding is available, a junction with the SWML and tunnel across to a junction with the SWML west of Newport.

Appendix 1 - Spurs:
1.) Spur from the M4/A329 (M) interchange at Winnersh Triangle, as a 2 track viaduct following the A329(M)/A3290 to just before the interchange with that road, then a short tunnel to a junction with the GWML (space for tunnel portal and junction to be created by displacing Southern Region Reading line alignment to the south for a few hundred metres on the approach to Reading station).

2.) Spur from Berks and Hants line approx. 500m east of Theale station to mainline HS5 viaduct alignment, to allow westbound HSL trains to rejoin after serving Reading.

3.) Tunnelled spur from the M4 approx 6 miles east of Swindon at Foxhill, to a junction on the GWML.

4.) Spur from the 4 track viaduct HS5 mainline, close to the M4/M32 split. Spur to follow M32 till junction 3, where spur would enter tunnel to a HSR station underneath the Temple Meads complex, and continue to a tunnel portal and junction south of the station for connections south.

 

[Thechopperguy]

Going to Portishead to cross the Severn is surely out of the question due to the terrain on the English side = hilly & you can’t go through the gorge.

I would suggest going west from Bristol Parkway following the present line that they plan to use for the Metro West to Chittening and then over the Severn on a barrage that would double up as a tidal power station. On reaching the Welsh side, a new station to serve Newport would be built by the docks and then the new line would proceed to Cardiff - but being as the present line here is straight, that would do with the reliefs being used for freights and local stuff. This would mean no more reliance on the ancient Severn Tunnel as well as being a short cut to Cardiff. Downside is no connection at Newport with the Marches line. No doubt the eco warriors would be on to this - as they have when a new M4 was proposed across the so called ‘wetlands’ = farmland reclaimed from marshes long ago and drained by reens - so not a natural wetland.

Anyway, what I think would be more realistic would be to get the IET’s running at their full speed of 140mph on the straighter sections of the GWML.

A new line between just south of Exeter & Newton Abbot would surely be of great benefit to the south-west - avoiding the route through Dawlish which would remain for local trains.

When they resignalled and electrified Newport - Cardiff, there was a plan to increase the line speed to 125, but it never happened.

I know it’s too early for it but how could a potential HS3 to the West look like. Currently the Great Western Mainline is at capacity between Reading and Paddington mainly because of the Elizabeth Line is hopefully this new line could divert existing GWR trains on the new line.

My vision would look like Paddington - Old Oak Common - Heathrow Central - Reading - New Bristol Cental Station? - Newport.

To cross the river Severn we will need to build a tunnel between Portishead and somewhere near the coast of Newport.

The most realistic way this would be built is by starting with Phase 1 between Paddington and Reading just to help alleviate capacity. Then Phase 2 between Newport and Bristol then Phase 3 between Reading and Bristol.

Benefits of HS3:

- Possibility to send GWR trains between Paddington and South Wales via Bristol which is a high demand destination.

- More capacity on the GWML so possibility to run additional Elizabeth Line trains, freight trains and even some more semi fast trains.

- Direct train connections between West England, South Wales and Heathrow Airport.

The idea 's fantastic but a more realistic proposition could be this. Take the GWML, increase the line speed from 125 - 140(current Great Western IET services timetabled for 125, but average speed is only about 70). Run limited stop services say, Paddington - Reading --Cardiff -Swansea and increase the OHLE as far as Swansea. This would take advantage of the speed capacity of the IET or even take it one stage further and make it full European loading gauge , and run Siemens Velaros from Swansea - Paris via HS1(via a bypass around London)

 

[Mgameing123]

I think going the whole way into Paddington would be too expensive, given Central London land values and the experience of tunneling into Euston with HS2.
The removal of GWR long distance services would permit extension of more Elizabeth Line services west from Paddington anyway, to carry the passenger load into central London.

I'm going to structure this in stages, to make this easier to read (the HSR London to Wales is referred to as HS5, it is 4 track as far as eastern Bristol, then 2 tracks into Bristol and 2 tracks westwards into Wales).

Stage 1: I'd build a large 6 platform terminus for the HS5 line at Old Oak Common, but on the current Cargiant site off Hythe Road.
Then I'd link it using a people mover to Old Oak Common HS2/Elizabeth Line/Heathrow Express Station and Willesden Junction for orbital connections around London.

Maybe a connection to North Acton for the Central Line too.

Stage 2: Then I'd build a tunnel from the HS5 Old Oak Common station to a tunnel portal by the M4 west of B454 Windmill Lane in Osterley.
Follow the M4 on a elevated viaduct as far as Heston services, then a tunnel towards a Heathrow station under Heathrow Terminal 3 (likely due for redevelopment by the time this is proposed).

Stage 3:  
Continued tunnel from Heathrow T3 HS5 station to the southbound M4 carriageway, west of Junction 5 for Slough East and Colnbrook.
Resumption of an elevated viaduct following the motorway as far as the M48/M4 split north of Bristol. (Yes, I know this is a long section, but this makes sense to minimise the land take of the railway within an existing transport corridor, as much as possible.)

Stage 4:
A new 2 track Severn tunnel from west of the M48/M4 split to west of Magor. 2 dedicated tracks alongside the South Wales Main Line/SWML until the outskirts of Newport (perhaps using the disused tracks south of the SWML). Either a junction with the SWML here only, or, if extra funding is available, a junction with the SWML and tunnel across to a junction with the SWML west of Newport.

Appendix 1 - Spurs:
1.) Spur from the M4/A329 (M) interchange at Winnersh Triangle, as a 2 track viaduct following the A329(M)/A3290 to just before the interchange with that road, then a short tunnel to a junction with the GWML (space for tunnel portal and junction to be created by displacing Southern Region Reading line alignment to the south for a few hundred metres on the approach to Reading station).

2.) Spur from Berks and Hants line approx. 500m east of Theale station to mainline HS5 viaduct alignment, to allow westbound HSL trains to rejoin after serving Reading.

3.) Tunnelled spur from the M4 approx 6 miles east of Swindon at Foxhill, to a junction on the GWML.

4.) Spur from the 4 track viaduct HS5 mainline, close to the M4/M32 split. Spur to follow M32 till junction 3, where spur would enter tunnel to a HSR station underneath the Temple Meads complex, and continue to a tunnel portal and junction south of the station for connections south.

Would there be a way to make Temple Meads a stop on the South Wales route.

== Doublepost prevention - post automatically merged: 3 Aug 2024 ==

I think going the whole way into Paddington would be too expensive, given Central London land values and the experience of tunneling into Euston with HS2.
The removal of GWR long distance services would permit extension of more Elizabeth Line services west from Paddington anyway, to carry the passenger load into central London.

I'm going to structure this in stages, to make this easier to read (the HSR London to Wales is referred to as HS5, it is 4 track as far as eastern Bristol, then 2 tracks into Bristol and 2 tracks westwards into Wales).

Stage 1: I'd build a large 6 platform terminus for the HS5 line at Old Oak Common, but on the current Cargiant site off Hythe Road.
Then I'd link it using a people mover to Old Oak Common HS2/Elizabeth Line/Heathrow Express Station and Willesden Junction for orbital connections around London.

Maybe a connection to North Acton for the Central Line too.

Stage 2: Then I'd build a tunnel from the HS5 Old Oak Common station to a tunnel portal by the M4 west of B454 Windmill Lane in Osterley.
Follow the M4 on a elevated viaduct as far as Heston services, then a tunnel towards a Heathrow station under Heathrow Terminal 3 (likely due for redevelopment by the time this is proposed).

Stage 3:  
Continued tunnel from Heathrow T3 HS5 station to the southbound M4 carriageway, west of Junction 5 for Slough East and Colnbrook.
Resumption of an elevated viaduct following the motorway as far as the M48/M4 split north of Bristol. (Yes, I know this is a long section, but this makes sense to minimise the land take of the railway within an existing transport corridor, as much as possible.)

Stage 4:
A new 2 track Severn tunnel from west of the M48/M4 split to west of Magor. 2 dedicated tracks alongside the South Wales Main Line/SWML until the outskirts of Newport (perhaps using the disused tracks south of the SWML). Either a junction with the SWML here only, or, if extra funding is available, a junction with the SWML and tunnel across to a junction with the SWML west of Newport.

Appendix 1 - Spurs:
1.) Spur from the M4/A329 (M) interchange at Winnersh Triangle, as a 2 track viaduct following the A329(M)/A3290 to just before the interchange with that road, then a short tunnel to a junction with the GWML (space for tunnel portal and junction to be created by displacing Southern Region Reading line alignment to the south for a few hundred metres on the approach to Reading station).

2.) Spur from Berks and Hants line approx. 500m east of Theale station to mainline HS5 viaduct alignment, to allow westbound HSL trains to rejoin after serving Reading.

3.) Tunnelled spur from the M4 approx 6 miles east of Swindon at Foxhill, to a junction on the GWML.

4.) Spur from the 4 track viaduct HS5 mainline, close to the M4/M32 split. Spur to follow M32 till junction 3, where spur would enter tunnel to a HSR station underneath the Temple Meads complex, and continue to a tunnel portal and junction south of the station for connections south.

The sad truth is that we will have to send the route into Central London for connectivity reasons. Which terminal though?

 

[GRALISTAIR]

Some great ideas. Won’t happen in my lifetime but I do love grandiose thinking.

 

[Topological]

Would there be a way to make Temple Meads a stop on the South Wales route.

== Doublepost prevention - post automatically merged: 3 Aug 2024 ==


The sad truth is that we will have to send the route into Central London for connectivity reasons. Which terminal though?

IF there was money to be spent then a rebuild of Parkway is needed. I do not know if a new one can be built East of the present one, but that would bring it closer to the M32 and would allow the present station to be kept open in the mean time.

I would build the station with through lines and hopefully that means the platforms etc could be built while trains were still running on the present (soon to be through) lines. The islands would be larger and allow for better cross platform interchange.

I would also take the chance to add Bristol facing bays in the new design so that there could be more shuttle trains into Temple Meads.

The actual London to South Wales trains would definitely stop at this new Bristol Parkway, as would the return of the fast Temple Meads to London trains. With 4 tph from the new Parkway to Reading and Paddington some could skip Swindon (though probably only 1 as I doubt it makes much difference to the schedule).

 

[61653 HTAFC]

Rather than a new Severn Tunnel, how about running over the top of the Severn Barrage?

( )

 

[HSTEd]

Rather than a new Severn Tunnel, how about running over the top of the Severn Barrage?

( )

Unfortunately, none of the proposed Severn Barrage schemes are particularly well positioned for such a function.

The two most common proposals are for Minehead-Aberthaw or Cardiff-Weston.
Even Cardiff-Weston is such a large detour that a new bridge would be cheaper!

 

[61653 HTAFC]

Unfortunately, none of the proposed Severn Barrage schemes are particularly well positioned for such a function.

The two most common proposals are for Minehead-Aberthaw or Cardiff-Weston.
Even Cardiff-Weston is such a large detour that a new bridge would be cheaper!

Well, it wasn't entirely a serious suggestion (as I'm sure you could tell) but I was thinking more along the earlier proposals for a barrage which were further upstream closer to Bristol.

 

[AlastairFraser]

Would there be a way to make Temple Meads a stop on the South Wales route.

As there is a new Severn tunnel (and indeed 4 tracking Temple Meads to near Bristol Parkway is planned now), you could run limited stop Devon - Somerset - Bristol - South Wales services using the existing Severn tunnel.

It would mean much better penetration of the population centres along the classic rail route than going via the High Speed line, so you would be able to justify a higher frequency with the higher passenger potential.

The sad truth is that we will have to send the route into Central London for connectivity reasons. Which terminal though?

I'm not convinced that you need to - at the end of the day, the Old Oak Common and Heathrow stations will have far more connectivity combined than any single central London station, and if central London is your final destination, the Elizabeth Line station at OOC offers a massive range of connections to whisk you into most of central London in 20 mins.

If you were absolutely convinced it had to be in central London, I would nominate Marylebone. There's space to the west of the platforms for a 4 platform station, as far north as Rossmore Rd.

It would require some compulsory purchase, but none of the buildings currently on site are of any heritage or architectural value I believe (unlike the existing neighbouring Marylebone station) and you could build some new very valuable real estate on top of the new station to relocate existing land users.

You already have the Bakerloo there, which isn't super busy and could be upgraded for higher frequency, plus room for a travelator tunnel to nearby Baker St and the tube connections there.

 

[Transilien]

I'm not convinced that you need to - at the end of the day, the Old Oak Common and Heathrow stations will have far more connectivity combined than any single central London station, and if central London is your final destination, the Elizabeth Line station at OOC offers a massive range of connections to whisk you into most of central London in 20 mins.

This would be politically unviable. The idea of South Wales and the West of England losing its direct service to Central London will make the idea of a high speed line unpopular with those who live in those areas and would probably lead to greater opposition than HS2 already has.

 

[AlastairFraser]

This would be politically unviable. The idea of South Wales and the West of England losing its direct service to Central London will make the idea of a high speed line unpopular with those who live in those areas and would probably lead to greater opposition than HS2 already has.

I'm not sure central London will be so much of an important destination by the time this project is being considered.

The centre of financial services has already moved before to the Docklands from the Square Mile, and there are big multi-use redevelopment plans for the OOC area that will be open for at least 10 years before this is even completed.

If there absolutely has to be a central London terminus, Marylebone is probably the most financially viable, without wrecking the released capacity benefits of the new line.

 

[Irascible]

As there is a new Severn tunnel (and indeed 4 tracking Temple Meads to near Bristol Parkway is planned now), you could run limited stop Devon - Somerset - Bristol - South Wales services using the existing Severn tunnel.

If you're boring a new one, I'm quite sure you'd want to get rid of the nightmare that's the old one. I think a bridge might be a better idea, though. Anyone know what state the current M4 bridge is in?

This would be politically unviable. The idea of South Wales and the West of England losing its direct service to Central London will make the idea of a high speed line unpopular with those who live in those areas and would probably lead to greater opposition than HS2 already has.

I'd be mostly annoyed that OOC doesn't have the same connectivity, I don't think I've ever got off a train into London & not gone somewhere else, even going to Moorgate. You'd need another Crossrail just to shift everyone else! ( at that point it might as well be HS3 under London... ).

Anyone want to ballpark some times for various routes? London-Southampton-<somewhere east of Bridgwater-ish>-Bristol/Exeter? ( add on Soton-Brum if you want ). London-Bristol via HSR paralleling the M4?

 

[Topological]

If you're boring a new one, I'm quite sure you'd want to get rid of the nightmare that's the old one. I think a bridge might be a better idea, though. Anyone know what state the current M4 bridge is in?



I'd be mostly annoyed that OOC doesn't have the same connectivity, I don't think I've ever got off a train into London & not gone somewhere else, even going to Moorgate. You'd need another Crossrail just to shift everyone else! ( at that point it might as well be HS3 under London... ).

Anyone want to ballpark some times for various routes? London-Southampton-<somewhere east of Bridgwater-ish>-Bristol/Exeter? ( add on Soton-Brum if you want ). London-Bristol via HSR paralleling the M4?

Current M4 bridge is being worked on at the moment, works ongoing all summer. Various contra-flows in operation.

OOC has a lot of potential, I actually think people would not be as wedded to Paddington as believed. If absolutely essential then extend one or two of the HS trains along the classic line to Paddington. I suspect the per-mile pricing would soon lead to everyone preferring OOC. (I cannot imagine a world where the OOC price is the same as the price to Euston on HS2 even).

 

[HSTEd]

Paddington is probably one of the worst positioned of the London Termini, if you draw a circle that encloses all london termini, Paddington and Marylebone are the two stations that together force the circle to be way larger than it otherwise would be.

With Paddington I make the circle ~3.45km in radius, with Paddington removed it is 3.05km. If you remove Marylebone it falls further to 2.6km.

I think your best option for a London terminus would probably be Waterloo, although that would probalby require Crossrail 2 to remove a lot of the traffic from it.

 

[MarkyT]

If you're boring a new one, I'm quite sure you'd want to get rid of the nightmare that's the old one. I think a bridge might be a better idea, though. Anyone know what state the current M4 bridge is in?

I've read that bridge options have been investigated before but maintenance costs would be significantly higher. With a new tunnel, the old one might be relined to create a drier environment. That might only leave space for a single track, but that would still be useful and a safe walking route could be provided alongside for access and evacuation.

I'd be mostly annoyed that OOC doesn't have the same connectivity, I don't think I've ever got off a train into London & not gone somewhere else, even going to Moorgate. You'd need another Crossrail just to shift everyone else! ( at that point it might as well be HS3 under London... ).

The point of the HS2 plan was that two London calls would have immensely greater connectivity in total than either one alone and would share the load. While OOC has the EL it doesn't have any legacy LU connections and any direct taxi journey from there into west end or city would be long and expensive.

 

[HSTEd]

I've read that bridge options have been investigated before but maintenance costs would be significantly higher. With a new tunnel, the old one might be relined to create a drier environment. That might only leave space for a single track, but that would still be useful and a safe walking route could be provided alongside for access and evacuation.

The cost of relining the tunnel, which may or may not actually solve the issues with the tunnel, would likely pay for a two track bridge to be converted into a four track bridge.

That would render the tunnel entirely redundant, I'm not convinced it would be at all worth it.

 

[Smwrff]

A new HS3 route from Bristol to Newport could follow the Shoots Barrage - and could also serve a new Severnside airport - to replace Cardiff & Bristol airports. But that would imply some sort of joined up thinking.... So will never happen....

== Doublepost prevention - post automatically merged: 4 Aug 2024 ==

A new HS3 route from Bristol to Newport could follow the Shoots Barrage - and could also serve a new Severnside airport - to replace Cardiff & Bristol airports. But that would imply some sort of joined up thinking.... So will never happen....

For those who might know, the Shoots Barrage is one of the proposed locations for a Severn Barrage - it would be located around 1km West of the existing Second Severn Bridge, so would be well placed to connect with existing SWML. A tunnel could be partially placed within the Barrage structure itself only reaching full depth under the main shipping channel. This could be built with or without HS3 - and I suggest keeping old Severn tunnel for freight only.

== Doublepost prevention - post automatically merged: 4 Aug 2024 ==

A Severnside airport has been proposed in the Estuary on the 'Welsh Grounds' south of Llanwern, so could easily be integrated with a rail line - Whether existing SWML or HS3.

 

[HSTEd]

A new HS3 route from Bristol to Newport could follow the Shoots Barrage - and could also serve a new Severnside airport - to replace Cardiff & Bristol airports. But that would imply some sort of joined up thinking.... So will never happen....

== Doublepost prevention - post automatically merged: 4 Aug 2024 ==


For those who might know, the Shoots Barrage is one of the proposed locations for a Severn Barrage - it would be located around 1km West of the existing Second Severn Bridge, so would be well placed to connect with existing SWML. A tunnel could be partially placed within the Barrage structure itself only reaching full depth under the main shipping channel. This could be built with or without HS3 - and I suggest keeping old Severn tunnel for freight only.

== Doublepost prevention - post automatically merged: 4 Aug 2024 ==

A Severnside airport has been proposed in the Estuary on the 'Welsh Grounds' south of Llanwern, so could easily be integrated with a rail line - Whether existing SWML or HS3.

A tunnel in the barrage would probably be ruled out on engineering grounds.
All the below water cross section of the barrage is going to be filled with turbines and their intake and outlet structures.
Trying to put a tunnel through it would impede the functioning of the barrage.

If such a structure is built it would be on a viaduct built into the top of the barrage structure.
Given how much of a pain the tunnel is it would likely be better to simply build however many tracks are needed to allow the Severn Tunnel to be abandoned.

Of course the problem with the Shoots barrage scheme is it requires people to support Tidal power enough to build such a scheme, but at the same time not support it enough to want to develop the resources of the estuary to a larger degree.

 

[Irascible]

I've read that bridge options have been investigated before but maintenance costs would be significantly higher. With a new tunnel, the old one might be relined to create a drier environment. That might only leave space for a single track, but that would still be useful and a safe walking route could be provided alongside for access and evacuation.

Crossing at Chepstow where the M48 bridge might be a little better. Ofc a tunnel would also be shorter too, I have absolutely no idea about the geology.

Paddington is probably one of the worst positioned of the London Termini, if you draw a circle that encloses all london termini, Paddington and Marylebone are the two stations that together force the circle to be way larger than it otherwise would be.

Yes. Having the Met/Circle/District/Bakerloo/XR there makes it massively more attractive than OOC though ( especially if OOC ends up being the end of HS2, although I don't know what world would build HSR to the bottom left of the country & not finish HS2 properly! ). South-west trains at least would need to be captive gauge so I guess you could run them into Padd P1, unless it's been irreversably shortened and I haven't noticed ( got to admit I haven't been in for a while ).

Waterloo would be great, if you can work out how to funnel a full main line domestic service into it ( if you're doing HSR to Exeter then I guess you're not running WoE past Salisbury, at least ). And, I guess, work out how to funnel all the extra passengers out of it. I guess we know where Crossrail 2 would be going...

Excuse me while I go for a wry chuckle about all this though . Local housing targets have been bumped up again with no sign of funding for any infrastructure at all ( and SWW are now bottom of the water providers table ), talking about this does make me grin. Maybe it really should just go to Wales.

 

[HSTEd]

Waterloo would be great, if you can work out how to funnel a full main line domestic service into it ( if you're doing HSR to Exeter then I guess you're not running WoE past Salisbury, at least ). And, I guess, work out how to funnel all the extra passengers out of it. I guess we know where Crossrail 2 would be going...

Crossrail 2 would presumably stay on its existing route, which would seriously cut the traffic into Waterloo by diverting all those passengers to Victoria et al.
I believe Waterloo is also not listed, which means a major reconstruction could be undertaken to allow long high capacity trains to use it.

Although to be honest, if we are going to the South West of England (rather than Wales), I would prefer to just run to Brighton and then along the coast.
That would fill the line by taking huge portions of the traffic off the Brighton Main Line, South West Main Line and eventually the Cornish traffic.

It would still be pretty competitive on journey time even if every train stopped every 30km - imagine a metro that runs 260-320kph.

 

[Irascible]

Although to be honest, if we are going to the South West of England (rather than Wales), I would prefer to just run to Brighton and then along the coast.

I still think going to Southampton and then splitting in Somerset somewhere could be fast enough for both the SW and Wales ( and add on Bristol to Birmingham, that would grab traffic to the north from a giant swathe of the south then - and tbh from rough sketching would probably be quicker to London even from Gloucester if you don't stop too much ). A Brighton/South coast metro sounds like it's own project, would admittedly dovetail in nicely.

That leads onto a question though - it's been discussed repeatedly that newbuild HSR is hardly more expensive than newbuild 125mph - but does that cover minimising environmental impact, like noise levels & so on? how do they scale with service speed, if at all?

 

[MarkyT]

I believe Waterloo is also not listed, which means a major reconstruction could be undertaken to allow long high capacity trains to use it.

ISTR some long high-capacity trains using Waterloo a few years ago! They used some modern part of the station that was constructed specially.

Although to be honest, if we are going to the South West of England (rather than Wales), I would prefer to just run to Brighton and then along the coast.
That would fill the line by taking huge portions of the traffic off the Brighton Main Line, South West Main Line and eventually the Cornish traffic.

In a recent video, Gareth Dennis proposed a WoE HS line roughly following the LSWR to Southampton then going along the south coast to Exeter. I think that's a better compromise for the far west than initially heading due south to Brighton. Not saying the Brighton main line also doesn't cry out for some improvements. The big scheme at Croydon would be a good start.

 

[AlastairFraser]

If you're boring a new one, I'm quite sure you'd want to get rid of the nightmare that's the old one. I think a bridge might be a better idea, though. Anyone know what state the current M4 bridge is in?

It is a nightmare, but there is a lot of demand for new frequent services from Cardiff to Bristol, serving the existing towns and suburban estates (e.g Patchway for the swathes of South Gloucs suburbia). A bridge is a possibility, but you'd still need a tunnel under Caldicot and Magor. We'll see what the plan has budget for when HS3 is likely to be designed in the 2040s.

 

[HSTEd]

ISTR some long high-capacity trains using Waterloo a few years ago! They used some modern part of the station that was constructed specially.

They then rebuilt the station to undo a lot of it! But what do I know.
(Even despite the sadness of the shortened platforms, the rebuild seems to be quite nice, I used it very recently for the first time since Eurostar moved out)

In a recent video, Gareth Dennis proposed a WoE HS line roughly following the LSWR to Southampton then going along the south coast to Exeter. I think that's a better compromise for the far west than initially heading due south to Brighton. Not saying the Brighton main line also doesn't cry out for some improvements. The big scheme at Croydon would be a good start.

Going straight to Southampton does shorten the line by about 50km, but at a reasonably pedestrian 260kph that is still only ~10 minutes.
I am not sure Southampton (possibly some of the traffic from Portsmouth but probably not all of it), Bournemouth and Devonwall is truly enough to challenge the capacity of a high speed line.

But I understand that a south coast super metro is rather a radical concept. 15+ (depends on platforming time) 400m high speed trains per hour stopping all stations doesn't really have much of a parallel elsewhere. The line would still be competitive or beat the conventional line on most journey combinations, with some being absolutely crushing. I would expect the frequency would be decisive thanks to negligible waiting times though.

 

[AlastairFraser]

Paddington is probably one of the worst positioned of the London Termini, if you draw a circle that encloses all london termini, Paddington and Marylebone are the two stations that together force the circle to be way larger than it otherwise would be.

With Paddington I make the circle ~3.45km in radius, with Paddington removed it is 3.05km. If you remove Marylebone it falls further to 2.6km.

I think your best option for a London terminus would probably be Waterloo, although that would probalby require Crossrail 2 to remove a lot of the traffic from it.

Problem is, you want to limit tunneling under central London as much as possible, and that there aren't many existing termini without Tube stations or other issues to work around.

Kensington Olympia is one option I hadn't considered, the District branch could be heavily upgraded to make access to central London very quick and direct. It's only 15 mins plus change time to e.g. Westminster today, and that time could be reduced with an upgrade.

== Doublepost prevention - post automatically merged: 4 Aug 2024 ==

I still think going to Southampton and then splitting in Somerset somewhere could be fast enough for both the SW and Wales ( and add on Bristol to Birmingham, that would grab traffic to the north from a giant swathe of the south then - and tbh from rough sketching would probably be quicker to London even from Gloucester if you don't stop too much ). A Brighton/South coast metro sounds like it's own project, would admittedly dovetail in nicely.

Southampton to Somerset would face absolutely interminable opposition from environmental groups, unless it was bored tunnel the whole way. The New Forest, Cranborne Chase and the Somerset Levels would all be on the route.

 

[Christian Schm]

In my view the issue is capacity east of Swindon, and the slow overall speed of Bristol/South Wales/West of England trains because of too many stops caused by this lack of capacity. So any HS West should start in London, then follow the A40 corridor, probably tunnel under the Chilterns, come up near Watlington, then two branches, one to Oxford, one to join the old line east of Didcot, with Didcot - Swindon (well, Wootton Bassett junction) four-tracked.

Service would be something like:
- Half-hourly to South Wales, with first stop Newport
- Half-hourly Bristol/West of England, with first stop Bristol Parkway
- Half-hourly Bristol via Bath, first stop Swindon
- Hourly Gloucester, first stop Didcot
- 4tp Oxford and onwards

In addition there would be normal expresses from Bristol and South Wales stopping at Swindon and Didcot and Reading and Heathrow if WRATH is build

 

[Irascible]

Southampton to Somerset would face absolutely interminable opposition from environmental groups, unless it was bored tunnel the whole way. The New Forest, Cranborne Chase and the Somerset Levels would all be on the route.

Well, let's face it, literally anywhere is going to face enormous opposition - you've gone from the south coast to the Bristol channel there anyway! don't forget the Mendips & Salisbury plain... then look at staying on the south coast. Wait for the riots in the New Forest next stop, a world heritage site!

You'd maybe have a bit more luck staying in the Mendips to go to Bristol, I think, and staying off the levels to go south too - ignoring environmental impacts I suspect they'd be a pain just engineering-wise. They do have a habit of flooding, too.

 

[AlastairFraser]

Well, let's face it, literally anywhere is going to face enormous opposition - you've gone from the south coast to the Bristol channel there anyway! don't forget the Mendips & Salisbury plain... then look at staying on the south coast. Wait for the riots in the New Forest next stop, a world heritage site!

You'd maybe have a bit more luck staying in the Mendips to go to Bristol, I think, and staying off the levels to go south too - ignoring environmental impacts I suspect they'd be a pain just engineering-wise. They do have a habit of flooding, too.

Which is why my plan would be following the M4 corridor; if you wanted to speed up regional and long distance journeys, another spur from just before the approaches of my proposed new Severn tunnel to the M49/M5 corridor (joining the conventional line at Highbridge) would be best.

You avoid as much difficult territory as possible, while still delivering a lot of benefits.

For improving journeys along the south coast to the South West, I'd be looking at full redoubling + electrification of the WoE line, then a new conventional 100mph line Dorchester - Bridport - Charmouth - Axminster along the coast.

Yes, it would still be quite difficult and would no doubt face a lot of opposition, but those 26 miles of new line would be better sized for the journey flow and connect several isolated places to the railway network.

 

[mike57]

Given the half finished mess that HS2 has turned into I doubt there will be any meaningful major rail infrastucture projects for a generation.

What could be done to improve journey times on the existing route? Average speeds London - Newport appear to be about 80mph, the ECML manages 100mph with 125mph running, and could 140mph running be a possibilty?

 

[The Planner]

Given the half finished mess that HS2 has turned into I doubt there will be any meaningful major rail infrastucture projects for a generation.

What could be done to improve journey times on the existing route? Average speeds London - Newport appear to be about 80mph, the ECML manages 100mph with 125mph running, and could 140mph running be a possibilty?

Bristol Parkway to Newport slows it down. You aren't going to do a lot with that. The only other easy option is to take Swindon out, you would save 5 minutes with that.