• Our new ticketing site is now live! Using either this or the original site (both powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!

HS2: Why do we need it?

Status
Not open for further replies.

Starmill

Veteran Member
Joined
18 May 2012
Messages
25,057
Location
Bolton
This incessant "personalisation" of politics where it's said to be one person's decision is really unhelpful and merely propogates an ignorance of how political systems actually work.
With all due respect, I think you don't know what you're talking about.

Firstly, the Prime Minister presented the policy personally. Note that the Secretary of State wasn't the one speaking, it was the Prime Minister.

Secondly, there was a speech about the policy change made at party conference. This was clearly done deliberately after days of leaking to the press, with official statements to the contrary just a week or so prior which then dried up - it was no mere oversight that the announcement was not made to the House, as is proper. No justification was given for sitting on the announcement until the recess, then choosing to announce days before the House could hear a statement either. This is not only a disrespectful way to treat us and our elected representatives, but it's also to throw the constitutional convention in the bin.

Thirdly, there was no government announcement with updated business case published. Indeed there was no busines case work whatsoever published. That's consistent with none having been done.

Therefore it's right and proper to criticise one man personally, the Prime Minister, for damaging our constitution and disrespecting our democracy, and indeed also for his shameful mismanagement of our money in this policy area. He's engaged in the worst type of policymaking, and is rightly receiving opprobium personally for doing so. His leadership, like those of his four predecessors, has consistently been weak in the face of duty, and he is guilty of prioritising himself and his power above all semblance of good government, in a way which prior to the second Cameron government had been very uncommon in the British political system.

If someone here is being ignorant of how the political system works, it's clearly not Benjwri.
 
Last edited:
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

Nicholas Lewis

On Moderation
Joined
9 Aug 2019
Messages
7,265
Location
Surrey
With all due respect, I think you don't know what you're talking about.

Firstly, the Prime Minister presented the policy personally. Note that the Secretary of State wasn't the one speaking, it was the Prime Minister.

Secondly, there was a speech about the policy change made at party conference. This was clearly done deliberately after days of leaking to the press, with official statements to the contrary just a week or so prior which then dried up - it was no mere oversight that the announcement was not made to the House, Not to do so is not only a disrespectful way to treat us and our elected representatives, but it's also to throw the constitutional convention in the bin.

Thirdly, there was no government announcement with updated business case published. Indeed there was no busines case work whatsoever published. That's consistent with none having been done.

Therefore it's right and proper to criticise one man personally, the Prime Minister, for damaging our constitution and disrespecting our democracy, and indeed also for his shameful mismanagement of our money in this policy area. He's engaged in the worst type of policymaking, and is rightly receiving opprobium personally for doing so.

If someone here is being ignorant of how the political system works, it's clearly not Benjwri.
He was only copying his two predecessors who were equally blatant.
 

Benjwri

Established Member
Joined
16 Jan 2022
Messages
2,371
Location
Bath
Fair point but his shadow chancellor tells us on a stuck record akin to get Brexit done that they will grow the economy by investing in critical infrastructure though. I know thats largely directed at renewables but that alone won't deliver net zero by any stretch of the imagination so they will need to bring transport into the mix. Clearly not going to change overnight.

On policy Labour don't have any serious ones yet and i suspect wont until the Torys launch the election campaign.
In my opinion given that Starmer specifically stated 'Yes. It's not going to happen.', a shift on the original line of effectively they needed to look into it more, it wont happen. The shadow transport minister has claimed that Labour will invest in the railways, which is obviously just talk at this stage, but it is fairly likely they will implement some kind of plan. However from what they've said I just don't think it will be HS2. Given the rhetoric they have pushed it sounds more like investment into existing lines and infrastructure, including electrification.
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
Had a route been devised that roughly followed the WCML at 300kph, would’ve this likely have been cheaper because of less need for tunnelling? Or maybe a more densely populated route would have cancelled out any cost savings…
The need for tunneling is largely not driven by simple engineering needs.

You could put a viaduct through the Chilterns if you wanted, but we can't because of political considerations.
Surface level construction is also politically difficult but also very challenging because it is the means with the greatest interaction with existing infrastructure.

Tunneling is turned to because it is the least politically fraught option and has the least interaction with any other infrastructure. Interactions are a nightmare for a project to deal with, which is why the surface section of HS2 along the New North Main Line alignment was replaced with a tunnel. And the cost growth is largely not a result of more tunnels, despite what some might claim.


In my opinion given that Starmer specifically stated 'Yes. It's not going to happen.', a shift on the original line of effectively they needed to look into it more, it wont happen. The shadow transport minister has claimed that Labour will invest in the railways, which is obviously just talk at this stage, but it is fairly likely they will implement some kind of plan. However from what they've said I just don't think it will be HS2. Given the rhetoric they have pushed it sounds more like investment into existing lines and infrastructure, including electrification.
Well the UK railway, outside of HS2, is burning through £12bn of "investment" per year as it is.

They could launch radical cuts to operational expenditure and still be "investing" huge sums.
The current situation is not politically sustainable in public finance terms, and the reckoning is coming.
 

Benjwri

Established Member
Joined
16 Jan 2022
Messages
2,371
Location
Bath
Well the UK railway, outside of HS2, is burning through £12bn of "investment" per year as it is.

They could launch radical cuts to operational expenditure and still be "investing" huge sum
And yet its still falling apart. I was referring to investment as in upgrades rather than maintenance to be clear.
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
And yet its still falling apart. I was referring to investment as in upgrades rather than maintenance to be clear.
Well the industry is in such a state that I'm not sure any meaningful reasonable amount of money would make much difference without major structural and systematic change. And there is no appetite within the industry for that or desire in the political management to expend political capital on forcing it.

Perhaps it would have been better if HS2 had been built in the M1 corridor as a London-Birmingham Shinkansen. At least then Phase 1 completion would allow major operational savings on the classic railway from rendering a large part of the current WCML service obsolete. As it is we will end up with a stub of track of only limited use and the WCML will continue bleeding money.
 
Last edited:

The Planner

Veteran Member
Joined
15 Apr 2008
Messages
17,661
Perhaps it would have been better if HS2 had been built in the M1 corridor as a London-Birmingham Shinkansen. At least then Phase 1 completion would allow major operational savings on the classic railway from rendering a large part of the current WCML service obsolete. As it is we will end up with a stub of track of only limited use and the WCML will continue bleeding money.
You have said this before, but what operational savings are there to be had and what money is the WCML bleeding?
 

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
104,250
Location
"Marston Vale mafia"
Perhaps it would have been better if HS2 had been built in the M1 corridor as a London-Birmingham Shinkansen. At least then Phase 1 completion would allow major operational savings on the classic railway from rendering a large part of the current WCML service obsolete. As it is we will end up with a stub of track of only limited use and the WCML will continue bleeding money.

As long as it went to Euston, is that not exactly what Phase 1 is? Where it's physically located is a bit irrelevant.

If you added a Chilterns Parkway you might take some of the traffic away from MKC if that's what you mean?
 

Energy

Established Member
Joined
29 Dec 2018
Messages
4,952
Perhaps it would have been better if HS2 had been built in the M1 corridor as a London-Birmingham Shinkansen. At least then Phase 1 completion would allow major operational savings on the classic railway from rendering a large part of the current WCML service obsolete. As it is we will end up with a stub of track of only limited use and the WCML will continue bleeding money.
I'm not convinced, you'd have to keep WCML Avanti services for Rugby and Coventry or spend loads tunneling underneath them to have a station anywhere near the centre.
 

Nicholas Lewis

On Moderation
Joined
9 Aug 2019
Messages
7,265
Location
Surrey
Well the UK railway, outside of HS2, is burning through £12bn of "investment" per year as it is.

They could launch radical cuts to operational expenditure and still be "investing" huge sums.
The current situation is not politically sustainable in public finance terms, and the reckoning is coming.
UK railway isn't burning through 12B a year in investment. Enhancements have been heavily scaled back to about 1B pa and then you have the renewals budget of 4B pa which isn't what i would classify as investment that just maintaining the status quo.
 

Tezza1978

Member
Joined
22 May 2020
Messages
261
Location
Warrington
Well the UK railway, outside of HS2, is burning through £12bn of "investment" per year as it is.

They could launch radical cuts to operational expenditure and still be "investing" huge sums.
The current situation is not politically sustainable in public finance terms, and the reckoning is coming.
Your figures - like many of your arguments re HS2 - just don't add up or make sense.

For a person on a railway forum, you seem extremely anti-rail. There are clearly major problems and issues with our railways reacting to staffing, wages, maintenance, TOCs and investment. But the doom and gloom spread by some on here, and the claim by some that an incoming Labour administration will spend zilch extra on rail because of the public finances /"it all needs to go on the NHS and pensions and Ukraine" is absolute nonsense.
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
You have said this before, but what operational savings are there to be had and what money is the WCML bleeding?
Even excluding subsidies direct to Network Rail, the West Coast franchise and West Midlands Trains are burning £320m per year between them.
If we equally share out the subsidy to network rail in proportion to total track access charges, track charges would something like quadrouple based on Network Rail's accounts.

WMT+West Coast paid something like £433m in track access charges, so spreading that would be comparable to a net deterioration in their financial situation of ~£1.299bn

So the two franchises, and I know they cover things that are not strictly the WCML but its the best data available, are net losing something like £1.6bn per annum once the subsidies hidden at NetworK Rail are brought into the light.

EDIT:

On the topic of operational savings, given previous experience even mentioning them leads to a firestorm.
Given this forum is a significant portion of my contact with people I'm not really comfortable discussing them.

But it would involve a lot of redundancies, various forbidden three letter acronyms and probably something resembling those proposed ticket office measures, although ideally rather better implemented.

EDIT #2:

There is a strange discrepancy in the data.
According to the rail finance records franchise operators paid £3.4bn in track access charges, but Network Rail only got ~£2.2bn.

Total track charges from HS1 are only around ~£400m a year and a lot of that goes to Eurostar rather than Southeastern.
Track charges for the valley lines are in the tens of millions of pounds a year, so I have no idea where the billion pounds goes.

That significantly improves the position indicated, but you are still looking at a net loss of over a billion a year.
 
Last edited:

Fazaar1889

Member
Joined
5 Oct 2022
Messages
601
Location
South East
Yes. Extra platforms released at Manchester Piccadilly and a very large release of capacity on routes through Cheadle Hulme would have been a huge transformation.
Thanks! Yeah that's what I thought. Good thing I still understand HS2 despite misinformation being thrown left right and centre
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
As long as it went to Euston, is that not exactly what Phase 1 is? Where it's physically located is a bit irrelevant.

If you added a Chilterns Parkway you might take some of the traffic away from MKC if that's what you mean?
The problem with HS2 Phase 1 as conceived is, unlike a Shinkansen, it has no ability to pick up intermediate traffic from major population centres along the route - because there aren't any.
As a result, whilst it might be able to relieve the WCML, it cannot (even partially) replace it.

MKC et al are goign to force retention of most of the existing timetable, and lots of people wish to add more services into the freed capacity. Which means the WCML is going to keep burning cash as it does now, but without the revenue from the ICWC services.
The rail industry's costs end up larger than they were before.

Sure you might pick up a chunk of extra revenue, but given HS2 is going to end up being mostly empty for the forseable given how things turned out, I'm not sure it can net improve the industry's financial or political position.

I'm not convinced, you'd have to keep WCML Avanti services for Rugby and Coventry or spend loads tunneling underneath them to have a station anywhere near the centre.

Well Rugby is by far the smallest of the settlements on the M1-to-Birmingham corridor, so I'm not sure its worth serving rather than letting it pick up a residual local stations service.
But Coventry and Luton would probably be the greatest challenges on the route for sure, but can't really tell without actually designing the thing.

Hard to tell from Google Earth or maps, as HS2 apparently found out to its cost.
 

Benjwri

Established Member
Joined
16 Jan 2022
Messages
2,371
Location
Bath
Well Rugby is by far the smallest of the settlements on the M1-to-Birmingham corridor, so I'm not sure its worth serving rather than letting it pick up a residual local stations service.
But Coventry and Luton would probably be the greatest challenges on the route for sure, but can't really tell without actually designing the thing.
Except stopping at either at anything but a Parkway station, which would do little to abstract from existing traffic because of the shear inconvenience compared to the existing station, or some unbelievably expensive tunnel under the city, which would require trains to slow down for its duration, nulifying the benefits of a high speed line entirely.

HS1 was never meant to abstract passengers between London and Birmingham, the idea was to remove trains heading to further North than Birmingham, allowing for more commuter services on the conventional lines. Whether that aim can be achieved anymore with the reduced scope is up in the air.
Hard to tell from Google Earth or maps, as HS2 apparently found out to its cost.
I think we all know that a significant amount more work than looking at Google maps went into route selection. No one could tell half the project would be cut off 10 years later.
 

350401

Member
Joined
5 Feb 2009
Messages
307
Yes. Extra platforms released at Manchester Piccadilly and a very large release of capacity on routes through Cheadle Hulme would have been a huge transformation.


Is it? This may have been the case two decades ago, but it's certainly not today!

Well, you're right they shouldn't have such power. But who is going to stop them? Parliament? Nope. The Courts? Definitely not. You?

Have you got some evidence this happened? It's widely reported in the press that the Department weren't informed ahead of time, let alone consulted. Most of the civil service staff found out about it at the same time the general public did. So it seems extremely unlikely to me that your claim here is true.

Again, this is naive. The cabinet are sycophants who do as they're told, and that's the end of it. They have been for some time.
I work on the project (all views my own), and can confirm 100% that zero HS2 staff, including the senior leadership team, were consulted by the government prior to the axing of phase 2. Its not a secret, indeed Sir John said the same at the Transport Select Committee. The reason for a lot of the current speculation on remaining scope, and what happens next, is that everyone at HS2 and the DfT are still working out how to get the best outcomes from what is left. It’s not yet decided.
 

Nicholas Lewis

On Moderation
Joined
9 Aug 2019
Messages
7,265
Location
Surrey
The problem with HS2 Phase 1 as conceived is, unlike a Shinkansen, it has no ability to pick up intermediate traffic from major population centres along the route - because there aren't any.
As a result, whilst it might be able to relieve the WCML, it cannot (even partially) replace it.

MKC et al are goign to force retention of most of the existing timetable, and lots of people wish to add more services into the freed capacity. Which means the WCML is going to keep burning cash as it does now, but without the revenue from the ICWC services.
The rail industry's costs end up larger than they were before.
Actually thats a good point and probably why they don't want to produce anymore business cases that look at whole industry impact.
 

JamesT

Established Member
Joined
25 Feb 2015
Messages
3,561
Had a route been devised that roughly followed the WCML at 300kph, would’ve this likely have been cheaper because of less need for tunnelling? Or maybe a more densely populated route would have cancelled out any cost savings…
The problem with trying to follow an existing route is how much has been built around it. If you’re trying to get into the towns and cities served by the WCML that’s a lot of demolition or tunneling. If you’re not trying to serve them, why follow the existing route when there are potentially cheaper and faster new alignments?
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
Except stopping at either at anything but a Parkway station, which would do little to abstract from existing traffic because of the shear inconvenience compared to the existing station, or some unbelievably expensive tunnel under the city, which would require trains to slow down for its duration, nulifying the benefits of a high speed line entirely.
It wouldn't be that "unbelievably" expensive, given the shear quantities of tunnels actually being built on the selected alignment.

And given even to Luton the journey time would be more like 14 compared to 25 minutes, a certain amount of inconvenience would be tolerable.

HS1 was never meant to abstract passengers between London and Birmingham, the idea was to remove trains heading to further North than Birmingham, allowing for more commuter services on the conventional lines. Whether that aim can be achieved anymore with the reduced scope is up in the air.
In the end this would only have been achievable if the public continued pouring lots and lots of money into the subsidies for the classic railway.
I'm skeptical if that was ever going to be the case, but now, in the post coronavirus world, it certainly isn't.

I think we all know that a significant amount more work than looking at Google maps went into route selection. No one could tell half the project would be cut off 10 years later.
A lot of people were very skeptical that anything like the full network would ever be delivered.
The scheme was designed such that it turns into a debacle unless the full Phase 2 is funded, and as it turns out none of Phase 2 will be funded, and we are stuck with a questionably useful stub.
 

SynthD

Established Member
Joined
4 Apr 2020
Messages
1,576
Location
UK
As a result, whilst it might be able to relieve the WCML, it cannot (even partially) replace it.
Relief was the intention. It’s an extra pair of tracks, not a replacement pair for the current two or three pairs. Where did you get this replacement idea from?
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
Relief was the intention. It’s an extra pair of tracks, not a replacement pair for the current two or three pairs. Where did you get this replacement idea from?
I accept that relief is the intention, the problem is I don't think this was a good plan.

It only makes sense if you believe that, however much the WCML loses, the government/public will be willing to pour that money in forever.
Even before coronavirus I would say this was a dodgy assumption, it is now a defunct assumption.

The business case for HS2 is "the good times will never end" made manifest.
 

Benjwri

Established Member
Joined
16 Jan 2022
Messages
2,371
Location
Bath
It wouldn't be that "unbelievably" expensive, given the shear quantities of tunnels actually being built on the selected alignment.

And given even to Luton the journey time would be more like 14 compared to 25 minutes, a certain amount of inconvenience would be tolerable.
Building the underground station would be pretty expensive is what I meant, significantly more than the tunnel itself. As I mentioned the biggest issue is you have to have drastically reduced speeds right from entering a tunnel with a station in it, even if not stopping, these would likely be even slower than on the conventional lines, and would entirely negate the benefits of HS2, it might even end up slower than it is now.
In the end this would only have been achievable if the public continued pouring lots and lots of money into the subsidies for the classic railway.
I'm skeptical if that was ever going to be the case, but now, in the post coronavirus world, it certainly isn't.
Rail travel will always require subsidies, without greatly increased costs, but there is increasingly little alternative given the challenges we face with emissions.
A lot of people were very skeptical that anything like the full network would ever be delivered.
The scheme was designed such that it turns into a debacle unless the full Phase 2 is funded, and as it turns out none of Phase 2 will be funded, and we are stuck with a questionably useful stub.
Okay but that doesn't mean the comment on Google Maps was at all deserved. The fault for that lies entirely with the government. If you are being paid to design a railway to the specifications of origninal HS2, you have to do that. You can't just go completely off spec because you think your employer will change their mind in 10 years.
 

may032

Member
Joined
17 Nov 2023
Messages
68
Location
London
I accept that relief is the intention, the problem is I don't think this was a good plan.

It only makes sense if you believe that, however much the WCML loses, the government/public will be willing to pour that money in forever.
Even before coronavirus I would say this was a dodgy assumption, it is now a defunct assumption.

The business case for HS2 is "the good times will never end" made manifest.
The WCML is the key rail artery in the UK. And rail numbers are recovering from Covid and expected to rise. Why would the it not continue to be subsidised given its immense importance to the UK economy?
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
Building the underground station would be pretty expensive is what I meant, significantly more than the tunnel itself. As I mentioned the biggest issue is you have to have drastically reduced speeds right from entering a tunnel with a station in it, even if not stopping, these would likely be even slower than on the conventional lines, and would entirely negate the benefits of HS2, it might even end up slower than it is now.
Would the station have to be underground?

There is quite a lot of space adjcent to the station in Luton that is being used for bus stops etc at the moment, plus the large car park on the opposite side of the station.
Coventry is more challenging in that respect but even there there is a lot of space adjacent to the station used by car parks.

Based on previous Shinkansen practice you only need two platforms and two through lines.
(EDIT: I don't suppose you have any info on Badaling Great Wall station in China? It's hard to get much info on it but it seems to be a high speed station in an underground cavern)

Rail travel will always require subsidies, without greatly increased costs, but there is increasingly little alternative given the challenges we face with emissions.
Road transport decarbonisation is proceeding and will continue to proceed.
The "decarbonisation" card has a specific sell by date and it is nearer than you might think, this is actually my professional area of expertise - well that and nuclear reactor engineering. Odd combination of skill sets but there we are.

Okay but that doesn't mean the comment on Google Maps was at all deserved. The fault for that lies entirely with the government. If you are being paid to design a railway to the specifications of origninal HS2, you have to do that. You can't just go completely off spec because you think your employer will change their mind in 10 years.
HS2's own directors are on record as stating that the project budget was set far too early in the process, before ground investigations and the like were complete.
If this is true then they were likely attempting to cost the railway from maps.

I was attempting to draw attention to the idea that map based surveys are inherently unreliable and must always be taken with a large lump of salt.

Given HS2's well documented problems with land acquisition and the like......

I'm not questioning that they designed a railway based around the original spec, the problem is the original spec was a bad idea for the railways future prosperity..
 
Last edited:

swt_passenger

Veteran Member
Joined
7 Apr 2010
Messages
32,902
The problem with trying to follow an existing route is how much has been built around it. If you’re trying to get into the towns and cities served by the WCML that’s a lot of demolition or tunneling. If you’re not trying to serve them, why follow the existing route when there are potentially cheaper and faster new alignments?
I think both the WCML corridor and M1 corridor options have been thoroughly demolished quite a few times since I joined the forum. It’s probably the same people proposing they should have been looked at almost every time. I think HS2 might have even published reports explaining exactly why they didn’t work…
 

The Planner

Veteran Member
Joined
15 Apr 2008
Messages
17,661
Even excluding subsidies direct to Network Rail, the West Coast franchise and West Midlands Trains are burning £320m per year between them.
If we equally share out the subsidy to network rail in proportion to total track access charges, track charges would something like quadrouple based on Network Rail's accounts.

WMT+West Coast paid something like £433m in track access charges, so spreading that would be comparable to a net deterioration in their financial situation of ~£1.299bn

So the two franchises, and I know they cover things that are not strictly the WCML but its the best data available, are net losing something like £1.6bn per annum once the subsidies hidden at NetworK Rail are brought into the light.

EDIT:

On the topic of operational savings, given previous experience even mentioning them leads to a firestorm.
Given this forum is a significant portion of my contact with people I'm not really comfortable discussing them.

But it would involve a lot of redundancies, various forbidden three letter acronyms and probably something resembling those proposed ticket office measures, although ideally rather better implemented.

EDIT #2:

There is a strange discrepancy in the data.
According to the rail finance records franchise operators paid £3.4bn in track access charges, but Network Rail only got ~£2.2bn.

Total track charges from HS1 are only around ~£400m a year and a lot of that goes to Eurostar rather than Southeastern.
Track charges for the valley lines are in the tens of millions of pounds a year, so I have no idea where the billion pounds goes.

That significantly improves the position indicated, but you are still looking at a net loss of over a billion a year.
Then you have choice, you either make the railways pay, in which case you are closing pretty much all of the network or you accept its not going to and it needs subsidy as a public service.
 

stuu

Established Member
Joined
2 Sep 2011
Messages
3,451
Based on previous Shinkansen practice you only need two platforms and two through lines.
(EDIT: I don't suppose you have any info on Badaling Great Wall station in China? It's hard to get much info on it but it seems to be a high speed station in an underground cavern)
Chinese Wikipedia has a bit more detail than the English version, using google translate it is pretty clear. It's two side platforms on loops off the main line, separate caverns for each platform
 

Benjwri

Established Member
Joined
16 Jan 2022
Messages
2,371
Location
Bath
Would the station have to be underground?

There is quite a lot of space adjcent to the station in Luton that is being used for bus stops etc at the moment, plus the large car park on the opposite side of the station.
Coventry is more challenging in that respect but even there there is a lot of space adjacent to the station used by car parks.

Based on previous Shinkansen practice you only need two platforms and two through lines.
The is space around the stations, but you need fairly long approaches to get the correct grade, plus exiting a tunnel in a town or city at speed creates challenges with booms, which would mean likely every train has to slow down, or you have to aquire large amounts of residential land all the way into the town for a new line.
(EDIT: I don't suppose you have any info on Badaling Great Wall station in China? It's hard to get much info on it but it seems to be a high speed station in an underground cavern)
the Shinkansen train design means they don’t suffer from ‘booms’, such a long nose was discounted for HS2 because of conventional line running.
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
18,644
The is space around the stations, but you need fairly long approaches to get the correct grade, plus exiting a tunnel in a town or city at speed creates challenges with booms, which would mean likely every train has to slow down, or you have to aquire large amounts of residential land all the way into the town for a new line.
Most other nations with high speed rail systems attack problems with booms by utilising large diameter tunnels.
As HS2 itself mentions in a blog post, the tunnels designed for HS2 make use of tunnel diameters below international norms.

Tunnels HS2 has designed for 360kph operation have diameters comparable to tunnels used for 250kph elsewhere.
That's why HS2 needs the giant tunnel hoods to avoid sonic booms, as the blog post notes, and this article quoting members of the design team corroborates.

Given that TBMs are available that are capable of bore cross sections above 150m2 and tunnel costs are only weakly related to diameter (Figure 4), there is a brute force solution available if necessary.

The trend elsewhere in the world has been to bigger and bigger tunnels to mitigate pressure pulse effects without big hoods, HS2 is more or less alone in its design choices.

Whilst far from ideal, even if trains were forced to slow down to 230kph on approach to station (matching the speed at the Stratford box in the middle of London) it would only have a limited effect on journey times, and in any case the line would remain far faster than the conventional railway.

the Shinkansen train design means they don’t suffer from ‘booms’, such a long nose was discounted for HS2 because of conventional line running.
Chinese trains don't have Shinkansen-style noses, because they use much larger tunnels than those that were typical practice in Japan.

Even Taiwan, which makes use of adapted 700-series Shinkansen (700T), has much smaller noses fitted to the trains than those in Japan because of their European profile tunnels.
The enormous noses seen in Japan are pretty much unique, Chinese trains far more closely resemble European ones in this respect.

This station is on a ~10km long tunnel section on a railway with a nominal speed of 350kph. So it does rather seem to have overcome this problem.
The likely answer is that the combined tunnels have a large enough cross section to absorb the pressure pulse from a train approaching at speed without causing serious problems for passengers on the platform.

Apparently the transition piece between single tunnel bores and the triple tunnel bore portion has a cross section of ~495m2!

At that point I'm fairly certain, from my physics background, that the train (with a cross section more like 12m2) will behave like it is in open terrain. Propagation of the pressure pulse into the platform tunnels will be comparatively small.

EDIT: Edited to add the figure number for the tunnel cost graph
 
Last edited:
Status
Not open for further replies.

Top