Mix of capacity on the GWML and Basingstoke junction I suspect will be the biggest factors, in addition to the revenue flow being primarily to central London and so slowing down those journeys by a diversion via Reading and stopping quite far from people's end destination doesn't make much headway with the DfT.
The interesting question on Southampton and Bournemouth is whether passengers would be willing to give up through trains to Birmingham and Manchester to allow a through service to Old Oak Common and Paddington.
I was not just thinking of domestic air travel. Not sure how soon but world wide air travel is going to have to reduce as the emissions are a problem.
My initial thought would be what form of traction would there be from Bournemouth to Paddington? We have third-rail at my end of things, a diesel bit from Basing to Reading and then dangly wires on to Paddington. Perhaps a new-build tri-mode 8xx?
Diesel all the way would be easier.
Given there's bi-mode 80x it would be rather silly not to at least make use of the wires. There's presumably not a lot of extra cost to add the third rail shoes once you have the electrical gubbins in there, although that does depend on what design of traction motors you use and whether you would need additional transformers to make use of the 750v DC supply.
The trend abroad has been for increasing tunnel sizes to avoid aerodynamic effects etc.
You mean like the Northern Hub project, that turned out great.
Why 530m? you don't need an extra 30m to split 2 x 250m sets. Why Tring, and why so slow? How does dumping itself at Hilllmorton/ Rugby alleviate any of the capacity issues when you are still running up the Trent Valley and along the Coventry corridor? Why do you need grade separation when you have bypassed the WCML and the crossing moves at Ledburn would be removed? What are you splitting at Warrington that you wouldn't at Crewe? I don't understand HS2 to Stafford when you are also proposing a bypass? What is the spur to Water Orton for? 4 tracks already exist between Water Orton and the approaches to New St. If you are going to Euston, why do you need a surface terminus at OOC? Crossrail on the WCML slows screws it up and doesn't release capacity for freight.
What are you basing that on? The Chiltern tunnels are 200mm wider than the 320km/h Saverne Tunnel on LGV Est. It's the same as the Gotthard Base Tunnel, a full metre larger than the Brenner Base Tunnel
I was under the impression that HS2 has specified 430m platforms for their 400m sets, but I may be wrong about that. (And it just so happens that 530m will accommodate 2 x 265m pendolinos if you want to double stack them in the early years.)
Tring is the nearest settlement beyond the Chiltern escarpment, so the end of the tunnel. Equivalent to Wendover for the HS2 Ltd route.
My understanding is that the most serious congestion on the WCML is south of Rugby. This proposal gives 6 tracks all the way to Rugby.
That's for if you want to run the WCML as a six-track railway, with crossovers between the high speed and the fast lines. It would give HS2 traffic access to Watford and Old Oak Common for Heathrow, and allow trains from Milton Keynes to access the direct tunnels to Euston. Plus operational flexibility for overnight maintenance etc.
Crewe, Warrington (change for NPR), Preston and Carlisle all seem to have space for 500m platforms relatively easily, so it makes sense to keep 500m trains on that section. Agree most splitting would happen at Crewe. (But a lot of people will get off at Warrington, especially if NPR is offering 8tph to Liverpool and to Manchester, so you might shorten sets there.)
I should have explained better. From Rugby South, cross the WCML, curve around the East of Rugby, head towards Coleshill, then join the current line of HS2 north past Handsacre onto the southern end of the Stafford Bypass. A delta junction near Rugby gives access to Leicester and Sheffield.
The Delta junction near Water Orton gives access to Central Birmingham, just like the current plan. But until Curzon St station/ Hauptbahnhoff gets built, you could run 250m units into New St, avoiding the congested Coventry corridor.
The original brief for HS2 specified access to Heathrow, and modelling suggests a third of HS2 passengers will get off at OOC. A surface terminus at OOC caters for this demand, without having to dig a station box 30m deep. And diverting some WCML trains that way reduces the load at Euston. If there's no demand for it, then I wouldn't do it.
The absolutely critical scarce resource is platform space in Central London. Paris shows how RERs can release platforms at termini to provide capacity for long distance services.
Pendos don't work in multiple, their couplers are for emergency use only, it's why they stopped dragging them to North Wales after Alstom told them.
300kph dual track tunnels are very much possible, like North Downs on HS1 though that's much shorter.
It's congested through pretty much everywhere, Coventry corridor... Colwich Junction... all busy.
I'd prefer tunneling through Birmingham and having a through station and tracks instead.
Surface? How are you getting surface tracks into Euston?
The Gotthard Base Tunnel's completed bore inner diameter is apparently 7.7m.
No, you just need the length of the two sets, depending on where the signal is.
Wendover is just because they shouted the loudest.
Build them both at the beginning and make it a proper speed, it would be cheaper for a start.
How do you alleviate the Cov corridor if you do that? You have also chopped out any connectivity to Birmingham Airport, its hinterland and the proposed growth around there by not going via Interchange. Birmingham International had 6.5 million entries and exits pre COVID. You would also need some pretty hefty grade separated junctions at the south end.
That flies in the face of providing capacity if you are now putting trains from HS2 to Watford and vice versa. Overnight maintenance is already dealt with on the WCML via two track timetables. You would build HS2 with a wide enough "6 foot" to allow bi-directional running with a safe cess.
That's a big dog leg to Birmingham.
How does that relieve the Cov corridor if you are still using New St? As above, you have just got rid of a massive multimodal interchange at the airport. How would the redesigned Curzon St be any cheaper than what is proposed?
Its not high speed. 125mph up to Washwood Heath where it slows down.
So you would need a grade separated junction for the OOC spur on the mainline? That reduces capacity unless its line speed where it joins the main line.
The plan for Crossrail on the WCML was 6tph to Tring, that absolutely knackers the slows and the ability to properly path freight and anything else.
Because I'd plan to access 10 platforms eventually, at perhaps 16-18tph.
I'm proposing an 8m diameter straight tunnel that's good for 300km, single track. But for the first 20 years, run trains on two tracks in the one tunnel, to save costs. The size of Kilby tunnel suggests speeds will be limited to around 120-140mph.
Sure. The next stage is to bypass Rugby (to the East), but merging onto the fasts at Rugby South gives you access to the Trent Valley and the Coventry corridor. There seems to be space to add tracks between Rugby Station and Rugby South.
I understood that the four tracks south of Rugby are more congested than the five / six tracks north of there. Is that not the case?
It's one station in London, instead of two; one tunnel out to the Chilterms instead of two; and half the length of high speed line. So best estimate (guess if you prefer) is half the cost.
accepted
I know what your aiming at. I would have preferred more manageable chunks myself but then how much is wasted on links to the WCML that will become temporary. Plus all the disruption to the parts of the WCML getting these (temporary) links built. I also wonder if the advantages that the London to Rugby section brings would have been good enough to make it worth while. Basically you are saving money by not addressing the capacity limits on the Coventry corridor and Trent Valley Line. I suppose this means one has to get a line to Birmingham in one go to get anywhere with temptation.
So why have HS2 Ltd built two tunnels under the Chilterns rather than just one slightly bigger one.
Point taken.
But it gets you East without having to build Birmingham to East Midlands Parkway
It wouldn't be. But would give far better connectivity than just Curzon St / Moor St as currently proposed.
You're probably right. But I still contend that it should be procured in stages, with honest review after each stage to learn how to do the next one better.
Okay, I must admit, I didn't think of emergency escapes, and having given it more thought I think I should've compared the Chiltern tunnels more to the Alpine base tunnels such as the Gotthard which, while much longer, is also single bore tunnels running great distances, rather than the North Downs Tunnel which is comparatively shorter.
To be fair, would you actually have to change anything in the existing tunnel if your primary limitation is aerodynamic?
