Fantasy: Major Infrastructure with Zero Chance of being Built

[Topological]

This thread is for highly speculative infrastructure suggestions that could be built with current technology, but would never be. If there is some plausibility then that is great, but certainly the cost-benefit does not need to wipe its face.

I will start with a tunnel from near Nailsea to the East edge of Cardiff such that all mainline services route that way. Electrification would be required and would cover Bristol Temple Meads. The result would be extra services between Bristol and London, some via Parkway and some via Bath. If kept, the Severn Tunnel would be for local services only. An added traffic generator would be buses from Nailsea (where 2tph through the tunnel would call) to Bristol Airport. Appropriate additional tracks would be added approaching Temple Meads using the available formation.

I have not done the maths to compare with the Marches, but Bristol to Manchester trains would be started back at Cardiff to use the tunnel. These, and the Cardiff to London, would be the Nailsea calls.

Any other great ideas out there?

 

[Tomos y Tanc]

This thread is for highly speculative infrastructure suggestions that could be built with current technology, but would never be. If there is some plausibility then that is great, but certainly the cost-benefit does not need to wipe its face.

I will start with a tunnel from near Nailsea to the East edge of Cardiff such that all mainline services route that way. Electrification would be required and would cover Bristol Temple Meads. The result would be extra services between Bristol and London, some via Parkway and some via Bath. If kept, the Severn Tunnel would be for local services only. An added traffic generator would be buses from Nailsea (where 2tph through the tunnel would call) to Bristol Airport. Appropriate additional tracks would be added approaching Temple Meads using the available formation.

I have not done the maths to compare with the Marches, but Bristol to Manchester trains would be started back at Cardiff to use the tunnel. These, and the Cardiff to London, would be the Nailsea calls.

Any other great ideas out there?

Given how old and leaky the Severn Tunnel is, your idea might not be that outlandish, although I think if the tunnel did need replacing a bridge crossing is more likely.

A Holyhead-Dublin tunnel is certainly doable but unlikely to wash its face, particularly post-Brexit and the virtual disappearance of the 'land bridge' freight traffic between Ireland and the EU.

At the end of the day all these things are political. As an example, the Lower Thames Crossing is a total non-starter by any rational analysis, yet it seems likely to happen anyway.

 

[Bald Rick]

I will start with a tunnel from near Nailsea to the East edge of Cardiff such that all mainline services route that way. Electrification would be required and would cover Bristol Temple Meads. The result would be extra services between Bristol and London, some via Parkway and some via Bath.

Youd need a new line all the way to Paddington for that…

 

[Topological]

Youd need a new line all the way to Paddington for that…

I must confess I was using the two paths for London to South Wales that are not going through the Severn Tunnel. The Swansea/Cardiff trains would be coming through my new tunnel and therefore serving Temple Meads en route to London. Do not want the whole thing becoming too silly.

 

[Sir Felix Pole]

A new high-speed line from Exeter to Plymouth, broadly following the A38. A few engineering challenges, but hey ho. Solves the 'Dawlish Problem' - what about South Devon you say - well a spur to Newton Abbot for residual services to Torbay / Totnes. Or if you want to be really bold a high-speed line from Exeter to Bodmin broadly following the A30 - it would make rail services to Cornwall competitive.

 

[Charlie978]

I propose a high-speed line from Manchester (or even beyond Bolton/Preston or Liverpool) to Sheffield and onto Nottingham or Derby via Chesterfield. Could help relieve Hope valley pressure and conventional lines to the south of Sheffield. Would never happen and would probably need a station upgrade in Sheffield to go along with it, but we can only dream.

 

[zwk500]

Given how old and leaky the Severn Tunnel is, your idea might not be that outlandish, although I think if the tunnel did need replacing a bridge crossing is more likely.

Given the demand for travel between Bristol and Cardiff, some way of increasing capacity is probably not too far off although exactly how is another matter.

A Holyhead-Dublin tunnel is certainly doable but unlikely to wash its face, particularly post-Brexit and the virtual disappearance of the 'land bridge' freight traffic between Ireland and the EU.

Agree here. Sadly, because it'd be nice to have a physical link from Ireland through to the continent.

At the end of the day all these things are political. As an example, the Lower Thames Crossing is a total non-starter by any rational analysis, yet it seems likely to happen anyway.

The LTC as a rational concept is very sensible. The Dartford Crossing is massively overloaded and building an alternative crossing is very sensible. Whether it's worth what it looks like costing is a different question.

 

[Topological]

I propose a high-speed line from Manchester (or even beyond Bolton/Preston or Liverpool) to Sheffield and onto Nottingham or Derby via Chesterfield. Could help relieve Hope valley pressure and conventional lines to the south of Sheffield. Would never happen and would probably need a station upgrade in Sheffield to go along with it, but we can only dream.

This makes me think of a High Speed 6

The top of the 6 is Leeds. The Delta junction is near the base with the right part being via Derby and Sheffield to Manchester and the left part being the route through Crewe to Manchester (where your proposed HS link comes in to complete the 6. HS8 can then link Sheffield to Leeds.

== Doublepost prevention - post automatically merged: 31 Jul 2025 ==

Given the demand for travel between Bristol and Cardiff, some way of increasing capacity is probably not too far off although exactly how is another matter.

I suspect that longer trains through the Severn Tunnel will be the best that is offered. But this is a thread for plausible, but unlikely projects and as you say there is a need for something better than the tunnel.

 

[A S Leib]

Continuous 25kV electrification from Wick to Whitland and everywhere in between (and further south and west), absent large government attitude changes.

I'd add Newcastle – Edinburgh – Edinburgh Airport – Dundee / Perth (– Highland Main Line bypasses; I don't know how much time that would save) to the high-speed line list.

 

[HSTEd]

I guess this is where I float my 505kph GB Metro.

Japanese SCMaglev trains running 12 trains per hour or so on a single stopping pattern, running from Cambourne to Aberdeen via Cardiff and London.
Turn up and go.
I assumed acceleration like a tube train to allow standing, but the actual Japanese trains accelerate substantially faster than that.



Journey times above in minutes, assuming a ~60 second dwell at each stop.
Average wait time about 150 seconds.

The track would have no pointwork moved in normal operation, with balloon loops provided in Aberdeen and Cambourne. Probably a couple provided in the middle of the line to allow for partial maintenance outages. This allows the high intensity despite the slow movement of maglev pointwork. Trains would be injected from one or two depots at the start of service and removed at the end of service, and other than with faulty trains no pointwork would move all day.

The extreme speed (a kilometre in about seven seconds) means the indirect route still absolutely crushes most journeys you can think of.

EDIT:
Fixed a pair of Typos! I've left the original attached.

 

[zwk500]

This makes me think of a High Speed 6

The top of the 6 is Leeds. The Delta junction is near the base with the right part being via Derby and Sheffield to Manchester and the left part being the route through Crewe to Manchester (where your proposed HS link comes in to complete the 6. HS8 can then link Sheffield to Leeds.

My ideal HS2 Alignment would have been to approach Birmingham from the South, and Have a north-south underground line leading directly to a north-south orientation under Manchester that then had Branches to Leeds via a Pennine Base tunnel (connecting to the ECML near Tollerton/Thirsk area) and WCML near Euxton Junction.

I suspect that longer trains through the Severn Tunnel will be the best that is offered. But this is a thread for plausible, but unlikely projects and as you say there is a need for something better than the tunnel.

The "ideal" fantasy tunnel is a for a new Weston-Penarth tunnel to provide circular Severnside services. A less insane but still rather ambitious ploy would be rebuilding the Sharpness-Lydney Bridge for Locals + freight. The actual outcome is probably a signalling rejig and, as you say, longer trains. Oh and Filton Bank electrification but that's not wholly impossible.

 

[stuu]

At the end of the day all these things are political. As an example, the Lower Thames Crossing is a total non-starter by any rational analysis, yet it seems likely to happen anyway.

Something like 25% of all this country's trade uses the Dartford crossing, it is entirely rational to increase the capacity there, and add redundancy too.

As to the actual topic, a proper metro for Bristol would be nice, I have crayoned a three-line network in the past. A medium capacity system like the VAL in Lille and Toulouse would be perfect. Not going to happen ever though

 

[Topological]

My ideal HS2 Alignment would have been to approach Birmingham from the South, and Have a north-south underground line leading directly to a north-south orientation under Manchester that then had Branches to Leeds via a Pennine Base tunnel (connecting to the ECML near Tollerton/Thirsk area) and WCML near Euxton Junction.

The "ideal" fantasy tunnel is a for a new Weston-Penarth tunnel to provide circular Severnside services. A less insane but still rather ambitious ploy would be rebuilding the Sharpness-Lydney Bridge for Locals + freight. The actual outcome is probably a signalling rejig and, as you say, longer trains. Oh and Filton Bank electrification but that's not wholly impossible.

My choice of Nailsea* to East Cardiff was to allow the trains to face Swansea - I am biased though. My argument is that such a route would be time competitive with via Newport as well as providing for Bristol to Cardiff demand.

I have previously thought about an alignment close to the Prince of Wales Bridge with the line running through Caldicot. That would be less expensive than my proposal, but does less for the Cardiff to Bristol flows.

 

[Charlie978]

My ideal HS2 Alignment would have been to approach Birmingham from the South, and Have a north-south underground line leading directly to a north-south orientation under Manchester that then had Branches to Leeds via a Pennine Base tunnel (connecting to the ECML near Tollerton/Thirsk area) and WCML near Euxton Junction

I think this is surely the alignment that makes the most sense in a network term.

 

[wanderingriver]

A Holyhead-Dublin tunnel is certainly doable but unlikely to wash its face, particularly post-Brexit and the virtual disappearance of the 'land bridge' freight traffic between Ireland and the EU.

Also one other issue would be that Ireland uses broad gauge while it's standard gauge in England. The only way I see it happening is with either a rail ferry and changing gauge on the ferry or one of those automatic gauge changers as it goes through the tunnel. It would probably be easier to Stranraer to Belfast post Brexit immigration wise

 

[CMS1]

Le Shuttle to Rugby (M6 M1 junction)?

 

[GRALISTAIR]

A new high speed line to relieve pressure on the northern WCML from about Wigan to Glasgow and Edinburgh without all the twists and turns and climbs of the current line.

 

[Russel]

Doesn't this thread cover almost every Government press release around public transport and infrastructure projects?

On that note, Rishi said the North Wales Coast was to be wired, how's that going?

 

[DM352]

A lower level Birmingham New Street taking the cross city and Walsall/Wolverhampton stopper lines

Related: Heard and could have been a rumour, there was a one off opportunity for another tunnel by proof house while the Bull Ring was redeveloped but was not taken.

 

[Mgameing123]

London to Beijing Maglev train and London to New York Atlantic Tunnel?

== Doublepost prevention - post automatically merged: 1 Aug 2025 ==

Also one other issue would be that Ireland uses broad gauge while its standard gauge in England. The only way I see it happening is with either a rail ferry and changing gauge on the ferry or one of those automatic gauge changers as it goes through the tunnel. It would probably be easier to Stranraer to Belfast post Brexit immigration wise

Not really a problem. You can either use gauge changers or build a standard rail line station in Dublin.

== Doublepost prevention - post automatically merged: 1 Aug 2025 ==

Youd need a new line all the way to Paddington for that…

That sounds like a job for HS3

HS3 Paddington to Newport

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...

www.railforums.co.uk

 

[Bald Rick]

My ideal HS2 Alignment would have been to approach Birmingham from the South, and Have a north-south underground line

That was looked at

A new high speed line to relieve pressure on the northern WCML from about Wigan to Glasgow and Edinburgh without all the twists and turns and climbs of the current line.

and so was that!

leading directly to a north-south orientation under Manchester

I *think* that was looked at, but Manchester was just a bit out of the way of Birmingham to Scotland on a decent alignment.

 

[daodao]

Any heavy or light rail tunnel under central Manchester.

 

[Austriantrain]

This thread is for highly speculative infrastructure suggestions that could be built with current technology, but would never be. If there is some plausibility then that is great, but certainly the cost-benefit does not need to wipe its face.

I will start with a tunnel from near Nailsea to the East edge of Cardiff such that all mainline services route that way. Electrification would be required and would cover Bristol Temple Meads. The result would be extra services between Bristol and London, some via Parkway and some via Bath. If kept, the Severn Tunnel would be for local services only. An added traffic generator would be buses from Nailsea (where 2tph through the tunnel would call) to Bristol Airport. Appropriate additional tracks would be added approaching Temple Meads using the available formation.

I have not done the maths to compare with the Marches, but Bristol to Manchester trains would be started back at Cardiff to use the tunnel. These, and the Cardiff to London, would be the Nailsea calls.

Any other great ideas out there?

Build HS2 as originally planned.

 

[zwk500]

A new high speed line to relieve pressure on the northern WCML from about Wigan to Glasgow and Edinburgh without all the twists and turns and climbs of the current line.

From Carnforth to Carstairs I think this line has a reasonable likelihood of being built tbh. Eventually...

That was looked at

and so was that!

I *think* that was looked at, but Manchester was just a bit out of the way of Birmingham to Scotland on a decent alignment.

I'm sure they were, they're hardly non-obvious options at a conceptual level. I'd contend that having a 'HS2 Core' of all trains serving London-Birmingham-Manchester would be more beneficial than the marginal JT improvement of a better route from B'ham to Scotland but then again I don't have all the data from the route selection study.
Although looking at the map, a dead straight line from Central Birmingham to Central Edinburgh passess though central Manchester (the direct line from Birmingham to Glasgow skirts the eastern edge of Warrignton). However I can completely see that by the time the route gets out of Manchester and has a junction for Leeds, it'd be too close for comfort to difficult terrain. Which then forces an underground, high-speed junction underneath Manchester....
One benefit of having a much simpler line is that there wouldn't have been so much negative reaction about who was going to be connected to what, and the Manchester-Leeds section would have been aligned with TRU, and NPR. Obviously so many deep-level stations under the biggest cities in the land was never going to happen, but still we can dream....

 

[Railwaysceptic]

Greatham to Middlesbrough with a bridge across the Tees.

 

[gg1]

Also one other issue would be that Ireland uses broad gauge while it's standard gauge in England. The only way I see it happening is with either a rail ferry and changing gauge on the ferry or one of those automatic gauge changers as it goes through the tunnel. It would probably be easier to Stranraer to Belfast post Brexit immigration wise

In the astronomically unlikely event a Holyhead to Dublin tunnel was every built, the gauge changer is so minor an obstacle as to be barely worth mentioning, it's proven technology.

If it was to happen I think the most likely layout would be a short standard gauge line from the Irish portal to the main Dublin station (probably either new platforms at Connolly or a totally new station), with a gauge changer there for any services beyond Dublin. The majority of the services through the tunnel would likely terminate in Dublin anyway so a little silly to mess around with changing gauge for that sake of 10 miles or so.

 

[Topological]

From Carnforth to Carstairs I think this line has a reasonable likelihood of being built tbh. Eventually...

I'm sure they were, they're hardly non-obvious options at a conceptual level. I'd contend that having a 'HS2 Core' of all trains serving London-Birmingham-Manchester would be more beneficial than the marginal JT improvement of a better route from B'ham to Scotland but then again I don't have all the data from the route selection study.
Although looking at the map, a dead straight line from Central Birmingham to Central Edinburgh passess though central Manchester (the direct line from Birmingham to Glasgow skirts the eastern edge of Warrignton). However I can completely see that by the time the route gets out of Manchester and has a junction for Leeds, it'd be too close for comfort to difficult terrain. Which then forces an underground, high-speed junction underneath Manchester....
One benefit of having a much simpler line is that there wouldn't have been so much negative reaction about who was going to be connected to what, and the Manchester-Leeds section would have been aligned with TRU, and NPR. Obviously so many deep-level stations under the biggest cities in the land was never going to happen, but still we can dream....

I would have put the Manchester station in Trafford and then that would have avoided all of these issues. Im not sure how much of the route would need tunelling from the airport either. Whether the junction for Leeds would have been near Bolton, or whether there would have been a separate East Manchester station I am not sure, my preference would have been the latter. The new Manchester Underground would provide the capacity to Salford Quays, University, Central Manchester and Etihad Campus. I think HS2 was a little obsessed with central stations which are inevitably much harder to build (and more expensive).

== Doublepost prevention - post automatically merged: 1 Aug 2025 ==

Doesn't this thread cover almost every Government press release around public transport and infrastructure projects?

On that note, Rishi said the North Wales Coast was to be wired, how's that going?

I think he got voted out, most rude (though this is not a politics thread and it is absolutely up to the current government what they want/think they can fund).

To be honest with batteries I am not sure that long electrification projects actually have as much value as a few years ago. It would be good to see some electrification around Llandudno Junction to permit battery operation on the routes over there, and something at Holyhead for charging. That passes plausibility, but probably also has more than zero chance of being built.

 

[zwk500]

To be honest with batteries I am not sure that long electrification projects actually have as much value as a few years ago. It would be good to see some electrification around Llandudno Junction to permit battery operation on the routes over there, and something at Holyhead for charging. That passes plausibility, but probably also has more than zero chance of being built.

Electrification still has all the value where it was always best - areas of dense service with high numbers of stops, or areas of long-distance high-speed running. Batteries will be impacting the case for borderline schemes that were more for operational reasons than traffic demand, such as Barnt Green-Redditch or Bournemouth-Weymouth (note I don't suggest these should be de-electrified, just that they likely wouldn't have been done if BEMUs were a viable option when they were done).

For North Wales, that likely means a decent case can be made for Warrington & Crewe to Llandudno (town), but beyond the Conwy to Bangor is likely to give a far worse return against a BEMU fleet. You might need a bit of wire from Holyhead to Menai Bridge just to ease the charging times though.

 

[bib]

Railways:
Some sort of higher speed Sheffield-Manchester route, if Sheffield-Derby is ~30mins for ~30 miles as the crow flies then something similar should be technologically doable albeit needing tunnels
A 100mph+ route linking Leicester and Coventry
Kinda think a big bridge from West Kirby over the Dee Estuary to Prestatyn would be cool

There's lots of stuff that could be done technically but would never happen due to cost/legal issues, lots of fast transport that we can't have because it is too expensive, eg Concorde, maglev, giant hovercrafts. I'd love it if they could put the world's fastest ferry on the Irish sea routes, over 60mph you could maybe do Holyhead-Dublin in 1hr and Liverpool-Belfast in about 3,

Energy related you could have some huge pumped storage/hydro schemes in scotland, or the Severn barrage

Roads, I wonder if there will ever be any new motorways built, or if they'll just keep upgrading A roads to Expressway levels

 

[signed]

Any bridge/tunnel ideas between Ireland and the UK

The Scotland-NI ideas are IMHO way too incovenient for access to the rest of the UK

A direct Holyhead-Dublin would be great but hard and expensive AF to build.

The most appealing, but the most expensive proposal, in my opinion is the Liverpool-Isle of Man-Ireland, serving 2 communities with better infrastructure in one go.