HS2 average cost per km is not a useful comparator. A comparison based on a HS2 section having the same proportion of tunnel etc as the Dawlish bypass would be useful. But HS2 Ltd are unwilling to provide costs of individual sections of their route.
The original documents provided ballpark figures per kilometre of each different type of civil engineering work required.
Maximum linespeed is a determinant of the route taken by a railway. Lower speed routes require less straightness, reducing the need for tunnels, etc. So it is nonsense to claim that a lower speed route requires "the same level of earthworks and other major engineering features" as a higher speed one.
But when you reduce linespeed, you are just decreasing the minimum curve radius. Instead of tunnelling through a landscape feature, you would be building a longer route around it. That isn't always necessarily any cheaper or better for the environment - tunnels are the best mitigation method available, and if you start building more surface civils, you'll need more mitigation to compensate.
Correct. There is no real need for them. As the 'Channel Tunnel Rail Link', HS1 was originally intended to carry only international trains. A domestic service was only added to justify the public subsidies for building the line.
The domestic service makes sense once you have committed to building the infrastructure. Would you now remove it?
There was no standalone case for HS1 domestic services. See above.
Wonderful. Is that relevant to this argument here?
There's no information on how many lines in Britain, Spain, Italy, or France would be 'capable of 230-250km/h with upgrades'. The East Coast, Great Western, and Great Central corridors are all likely to be suitable for 250 km/h operation.
Indeed the Great Western probably is between London and Bristol. However, the ECML probably isn't, because although it may be for the most part very straight, the relevant figure is the curve radius where it isn't and it doesn't look pretty. Even York to Darlington isn't that straight given that it has a non-significant bend right in the middle which will cap top speeds.
In Germany, the railway operator and authorities did not permit >160km/h running without special signalling, similar to how >200km/h running is not allowed in the UK without it. Since they brought in that signalling system, it means there is no special figure at which track speeds would be capped. For example, Network Rail would never previously bother approving the GWML track for >200km/h running because there would be no way to run trains over it at that speed. Had in-cab signalling and increased speeds been introduced under BR, then I can't see it being a problem, but since they weren't, the network has developed in such a way which will make it much more difficult to implement in future.
Class 395 has to be able to run on the HS1. Which, in your parlance, 'runs' at 300km/h.
You are being deliberately obtuse because you know your arguments are specious.
Because I'm holding you to the same standard you demand of me. If you don't want me to criticise you for being subjective, you have to back up what you say with referenced facts and figures. If you can't be bothered to do it, don't criticise me for doing the same.
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Removing the fake 'need' for 400 km/h speed would have allowed a choice from much wider range of routes, or re-use of the southern Great Central formation.
HS2 doesn't reach 400km/h until it has exited the Chilterns Tunnels. From then on, it uses the Great Central formation as much as it can, given that the Great Central passes close to or through towns and villages. You can't reopen a fast railway of any speed through a variety of towns and villages without causing upset, and any major towns would need to have the same sorts of bypasses built just as far away. If you're going to need to stay a few kilometres away from any major town, you're going to have a wide curve radius.
HS2 Ltd have been asked for, but have failed to provide, detailed information about the infrastructure costs associated with different maximum linespeeds.
Because there is no major gradient in costs. A 400km/h viaduct will have only just a bit more concrete in it than a 300km/h or a 200km/h one, and the construction impact will be almost the same.
So, what is the additional journey time arising from running trains at 250 km/h maximum to Manchester and Birmingham? And how many more people would find it just as quick to drive?
Are you seriously suggesting that the Government wants to spend more money than they need to, given the difficult politics of the scheme?
The 400km/h top speed is intended to allow London-Scotland journeys of just above two hours in the future. If Great Britain ended at Preston, we wouldn't be building HS2 like we are.
There would need to be a business case for running trains at 250km/h that was better than the case for 330-360-400km/h for it to be worth doing. That takes into account any (minor) reductions in cost as well as the resulting economic and commercial effects. Network Rail didn't think a 250km/h railway was worth building back in their New Lines Programme, and they're the people whose job it is to make the railways work. If you know better, then why don't you present your ideas to them? Even the HSUK people think that >300km/h is the way to go.