HS2 future northern extensions

[NotATrainspott]

Assuming you can actually get to a point where the reduced capacity of a single track scheme matters.
And we are not going to get near that for this Scotland route.

Your single track high speed railway would be ruinous for capacity on Phase 1. You need as much possible slack (i.e. time saving by running at 360km/h rather than the timetabled 330km/h) as possible to get all the trains in the right order by Birmingham. Single track with passing loops wouldn't let you do any of that unless you want to end up with a route which is more double-track than single track, at which point you're not saving much money by doing that in the first place. Double track sections would need to go where the timetable demands rather than where it's cost-effective. Even then, I don't think you're going to get a lot of a cost saving even where you have twin-bore tunnels, as their safety case relies upon having intermediate cross-passages. Instead of having a shaft every three or so kilometres and a cheap cross-passage every few hundred metres you would have to have a shaft every kilometre or so, or have a parallel escape bore. Really, there's not a vast amount of point in building single-track high speed lines, especially when they require a lot of new civil engineering.

That said, there are actually single track high/higher speed railways. The French have plans to build an LGV branch line between Poitiers and Limoges, which will be single track 320km/h with passing loops. One of the more distant Spanish LAVs has been half-built with some of the separate civils for the second track left unfinished. There's also a higher-speed line in Sweden built as single track with passing loops. Normally, the economics of building a new line require the old line being busy enough to justify double track in the first place, but it seems that some European countries just build HSR lines for the sake of speeding up every journey rather than because it's genuinely necessary.

 

[HSTEd]

Your single track high speed railway would be ruinous for capacity on Phase 1. You need as much possible slack (i.e. time saving by running at 360km/h rather than the timetabled 330km/h) as possible to get all the trains in the right order by Birmingham. Single track with passing loops wouldn't let you do any of that unless you want to end up with a route which is more double-track than single track, at which point you're not saving much money by doing that in the first place.

Or you just put five minutes of slack in the timetable with a wait at Wigan?
And if you stack the Edinburgh and Glasgow paths north and south next to each other in the timetable it doesn't particularily matter which actually leave first, since the computer would have plenty of time to adjust the points in the time it takes for the trains to actually reach Wigan.

HS2 will run on an hourly clockface timetable since there is no reason not to on such a newbuild and simple network - as long as trains are in position to use the proper core paths each hour it doesn't really matter which trains is which on any given cycle.

Double track sections would need to go where the timetable demands rather than where it's cost-effective. Even then, I don't think you're going to get a lot of a cost saving even where you have twin-bore tunnels, as their safety case relies upon having intermediate cross-passages. Instead of having a shaft every three or so kilometres and a cheap cross-passage every few hundred metres you would have to have a shaft every kilometre or so, or have a parallel escape bore. Really, there's not a vast amount of point in building single-track high speed lines, especially when they require a lot of new civil engineering.

But if we are going for a minimum cost scheme there is very unlikely to be a significant number of new tunnels required, as we would likely use a derogation similar to that granted in Germany which would allow 4% gradients.

Indeed you could probably do it without a single wholy new tunnel at all.

 

[class26]

Assuming you can actually get to a point where the reduced capacity of a single track scheme matters.
And we are not going to get near that for this Scotland route.

But single lines will impact on reliability which in turn will impact on usage and therefore revenue for what seems minimal savings if any at all. Can`t see the point.

I remember when I was a student in Birmingham and the M5 was being built as a 2 lane motorway everyone was saying how stupid it was and low and behold later an extra lane was added at reportedly 10 times the cost than if it had been put there in the first place. Virtually every bridge had to be replaced as they were not wide enough
Nice one DFT.

 

[HSTEd]

But single lines will impact on reliability which in turn will impact on usage and therefore revenue for what seems minimal savings if any at all. Can`t see the point.

It would be far more reliable than the alternative which is likely to continue to crawl along on the classic line.

Dedicated high speed rail lines with no track sharing are capable of achieving sustained periods of to-the-second accuracy.

 

[class26]

It would be far more reliable than the alternative which is likely to continue to crawl along on the classic line.

Dedicated high speed rail lines with no track sharing are capable of achieving sustained periods of to-the-second accuracy.

Yes, but my point is IF the savings are so small as stated above why bother to build a single line when for a tiny bit more you can build 2 tracks ?

 

[HSTEd]

Yes, but my point is IF the savings are so small as stated above why bother to build a single line when for a tiny bit more you can build 2 tracks ?

Because earthworks and the like are a relatively small component of the price of a high speed line.
You will require infinitely more signalling equipment, electrification infrastructure and all sorts of other subsidiary works.


If we were building an S shaped line instead of Y it would be difference, but the maximum path count on the core is tiny anyway.

 

[class26]

Because earthworks and the like are a relatively small component of the price of a high speed line.
You will require infinitely more signalling equipment, electrification infrastructure and all sorts of other subsidiary works.


If we were building an S shaped line instead of Y it would be difference, but the maximum path count on the core is tiny anyway.

I refer the honourable gentleman to post 479 where Haydn 1971 states that the earth works are a very large portion of the cost. The opposite of your statement above. Do you have any experience or is this just a gut feeling ? i believe that Haydn 1971 (post 479) has had experience in actual costing for such jobs and therefore ought to know what he is talking about.

 

[miami]

Not sure how signaling for a single line would be cheaper than that for a double line.

 

[HSTEd]

Not sure how signaling for a single line would be cheaper than that for a double line.

Well since we don't yet have ERTMS Level 3 there would have to be a vast succession of track circuits covering the entire system on a double track line to allow multiple trains to follow each other relatively closely.

All these circuits have to be designed, fitted and tested, and have to be supplied with multiple redundant sources of power (they cannot be simply suppleid from the traction supply because the signalling system must be able to handle the opening of a traction substation circuit breaker).

Providing diverse power supplies to equipment spread in a several hundred kilometre long line through the kind of terrain we are talking about is not simple or cheap.

Single track lines only have a handful of points alnog the route that actually have to be supplied with power - the sections between the loops can be operated as single long blocks with axle counters at each end.
You also avoid the vast numbers of trackside cables that would be required for all this equipment spread along the alignment.

Additionally since the number of tranis that can physically be on the route at once is very small the traction supply can be far 'weaker' than would otherwise be the case.
--- old post above --- --- new post below ---

I refer the honourable gentleman to post 479 where Haydn 1971 states that the earth works are a very large portion of the cost. The opposite of your statement above. Do you have any experience or is this just a gut feeling ? i believe that Haydn 1971 (post 479) has had experience in actual costing for such jobs and therefore ought to know what he is talking about.

That post seems to be referring to earthworks for bridges and the like - these are drastically cut down than would be seen in typical British High Speed rail projects - which tend to be in far denser terrain where people complain about views a lot more.
With relaxed gradients it seems likely you could 'follow the lie of the land' a lot more than would otherwise be the case.

And I humbly, not being a rail industry professional, that if building single track lines cost only 10% less than double track ones - noone would ever build single track ones.

 

[miami]

Well since we don't yet have ERTMS Level 3 there would have to be a vast succession of track circuits covering the entire system on a double track line to allow multiple trains to follow each other relatively closely.

But your premise is multiple trains don't need to follow each other relatively closely. With 2 trains per hour per direction at 186mph that means you could have a 90 mile gaps between the trains. Put a signal box at Crewe, Lancaster, Carlilse, and Biggar/Carstairs/etc.

Isn't that how block signalling works?

 

[HSTEd]

But your premise is multiple trains don't need to follow each other relatively closely. With 2 trains per hour per direction at 186mph that means you could have a 90 mile gaps between the trains. Put a signal box at Crewe, Lancaster, Carlilse, and Biggar/Carstairs/etc.

Isn't that how block signalling works?

Indeed you could - but now you have just spent that extra 10% (or whatever percentage) on the rails and right of way infrastructure and got essentially no extra capacity.

And as we find out to our cost today resignalling the line later is likely to cost some enormous sum of money - so much so we could probably build a significant fraction of second line.
Tampering with things while they are open is going to be expensive, very very expensive.

There seem to be only two half way feasible options - the minimum cost scheme or the full blown one. There is little in the middle that makes much sense as you lose the benefits of one long before you pick up the benefits of the other.

 

[222ben]

Connect it with the Great Western Main Line better. and Make a HS line to Bristol and Exeter. My main gripe about HS2, not connecting with current main lines. but that would take billions probably.