No offence like but Blad Rick knows his onions when it comes to this sort of thing - he does it for his job I do believe
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Why are people opposed to HS2? (And other HS2 discussion)
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No offence like but Blad Rick knows his onions when it comes to this sort of thing - he does it for his job I do believe
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OLE - it’s essentially the same once you get above 125mph. Signalling - exactly the same. Track - the choice of slab is nothing to do with speed, and everything to do with maintenance. You don’t need slab track to go above 140mph, or above 200mph for that matter. And the track spec is the same at 140 as 200. The trains - marginal difference. Electricity: I’ll give you that one, it would mean slightly smaller transformers at the grid connections.
R G NOW.
Member
I thought HS2 was to be 125mph running only with conventional signalling, maybe I dreamt it somewhere, I don't know.
The question I've always had when seeing that figure is how slow is a non High Speed line?
If it's 140mph then there could be an argument that is worth doing as you'd save £5.5bn and probably wouldn't need to spend that much more on the trains this time around (although when there's trains are replaced the overall costs would be higher).
If it's 100mph then you'd likely need twice as many trains and given they've been costed as £7.5bn that's going to wipe out the cost savings this time around in buying the trains, even if you assume a 1/4 saving on the trains.
So passive provision for for 400, 350, (or even 320/300) km/h would require the same alignment and virtually the same clearances. It could even be slightly more expensive as a lower maximum speed would require more attention to gradients.
Then there is the provision of stations. To provide for future capacity demand, it would be folly to build a line that couldn't handle 400m long trains, so there would be no land saving on the stations (or box for OOC) and there would need to be protected space for stabling/maintenance/loops to prevent future opportunist caving in to developers. The Series 1 OLE would probably be cheaper to install and maintain than the knitting along the GWML where so many junctions and crossovers have been wired. As Bald Rick says, slipform paved track is not mandatory for high speed and for a new railway, might just be considered as a through-life saving worth investing in.
So all-in-all, not much saving to be had at all after the additional trains and their taff requirements are priced in.
Bletchleyite
Veteran Member
I meant passive provision for 400 metre trains, e.g. by way of infrastructure positioning.
For new lines it’s 200kph / 125mph. Up to that speed the Conventional Rail Systems INF Technical Standards for Interoperability (TSIs) apply. Above that the High Speed Rail System INF TSI applies.
The only real variations in standards above 125mph relate to alignment, track separation (progressively wider with speed, but the widest gap is only 500mm wider than the narrowest), and pressure differences in tunnels.
Clearly a lower speed railway can have a more curved alignment, both vertically and horizontally. But the alignment for HS2 Phase 1 is now fixed in law.
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Well what I do for a job is a closely guarded industry secret
But I will admit that in the earlier stages of my career I have been involved in projects building new railways, both conventional and high speed.
Sorry, I've read too many posts on the subject just before I posted. So I assume that would include the items that I mentioned above?
Thanks, so we'd only save circa 9% if the speed of the new lines were less than 125mph.
As such no faster than WCML, so why would anyone use it?
Strictly speaking, less than 201kph.
And I don’t know where that 9% comes from, but it will be, at best, a very rough average based on a wide range of new railways. Given the alignment for HS2 phase 1 is fixed, and that several billion pounds has already been spent on land, enabling works and design, the saving for reducing the speed to <201kph will probably be negative. Ie it would cost more, as all the things that have been designed would have to be redesigned.
jfowkes
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What would be the impact on capacity of reducing the design speed? With the reduced headways, how many more trains/people could run per hour relative to the current design?
As Bald Rick says, this is a largely academic discussion, but interesting.
As Bald Rick says, this is a largely academic discussion, but interesting.
Bletchleyite
Veteran Member
Yes, it would need the land, just not e.g. the platforms.
Esker-pades
Established Member
The same number of trains per hour could still run, but more rolling stock would be required for the full service (a round trip takes longer when going slower). Thus, the cost increases.
As although it may save a bit this time around, by the time you order the replacement set you're looking at higher costs.
jfowkes
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Really? In my role as "layperson-who-has-read-a-tiny-bit" it seems to me that speed reduction would allow you to run more trains, closer together, which would result in a greater people-per-direction-per-hour. What am I missing?
You'll struggle to get higher than 20 paths/hour (18 considered the maximum that can be used) that HS2 provides without using Metro stock to reduce dwell times and/or really slowing down (eg London Bridge-Charing Cross or Thameslink core) - rendering the line terrible for intercity journeys.
jfowkes
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That makes sense, thanks. I assume the problem with Metro stock is that it just isn't designed for long journeys? Like, there's no technical reason why metro-style stock can't run at HS2 speeds?
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Yes, sorry, "had enough of...".
In any case, with huge infrastructure projects of course money gets siphoned off into the companies of those who promote big projects. That's not much of a reason to oppose them. Should we stop funding any new projects because construction companies, e.t.c will be better off from them?
Well quite:
New screening equipment in hospitals - profits to screening equipment manufacturers.
New aircraft for the RAF - profits to aerospace companies
New school buildings - profits to the construction industry
Etc.
To my mind, headways at a reduced speed would be shorter in distance but the same in time. At 320km/h, a flow of 18tph would give a linear separation of over 17km. At 225km/h at the same frequency, the separation becomes 12.5km. I assume that both of those would be acceptable on a plain railway with (presumably) moving block cab signalling no features requiring abrupt speed reductions in normal operation. If a HST can manage a 2km emergency stop and that was designed over 40 years ago, trains being designed now should probaby OK with the headways planned. The signalling would probably also be configured for energy conservation, so apart from an emergency stop, much of the reduction in speed would achieved with coasting and moderate regenerative retardation. Therefore the volume of passengers could be the same but each taking longer to travel the distance, and as has been said, requiring a larger fleet of trains.
The technical headway (what the signalling permits) of the WCML fast lines at 125mph is actually around 75 seconds, ie in theory you could have 48tph. At this headway trains are around 2.5 miles apart - more than twice as long as the braking capability of the rolling stock.
However it is not the plain line sections that are the capacity constraints, but the convergences, divergences, stations and any speed restrictions. It is this that limits route capacity, rather than looking purely at line section capacity. Add in a little margin for error and that’s why the WCML fasts operate on a 3 minute planning headway (what the timetablers use). Indeed I have just seen 2 trains on the down fast exactly 2 minutes apart.
On HS2, At 250mph the braking distance effectively quadruples, and the distance between trains will not quite quadruple (as the signalling overlap will be broadly the same), and thus the technical headway will be around 140 seconds. ETCS helps here a little. However you still have most of the other issues re the limitations to route capacity, albeit not quite as constraining, and thus a planning headway of 3 minutes is still very achievable.
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It’s the bit after “experts” that is important.....but he was getting so rudely interrupted few noticed.
You missed the point. I don’t have a problem with industry people making money from HS2, but it is a reason why you can’t just take “all the industry experts support HS2” without some cynicism. HS2 their industry gets £50b+, no HS2 they get none of that.
So we shouldn't take the opinion of doctors on health policy? Or military on military policy? Or teachers and lecturers on education policy?
Strawman. It's not drivers and guards wanting HS2, it's politicians and consultants.
And some of the public depending on how you view it. You are full of strawman arguments and whenever you are challenged on them you fall back on your 'im just a normal person who doesnt understand' which is the biggest cop out ever. Lets face it - you simply have not come up with one simple and decent reason why HS2 should not go ahead - not one. Ever.
Policy is very different from whether or not to spend £50bn+ on one project, and doctors, soldiers and teachers aren’t company directors or consultants needing workflow
And rail industry professionals* whose job it is to plan future railway capacity.
(*Don't read that as be saying drivers and guards aren't professional!)
Seriously? It would make no difference to the opponents. Their main objection is to the existence of the route at all, especially if it goes anywhere near their houses etc*, followed by any expenditure of money whatsoever. Most people in the UK have not been on a train for years and just don't see the point or need for them. They don't know the difference between Thomas the Tank Engine's railway and a modern high speed one, let alone the difference between two different levels of high speed. They just don't care, and just hate railways.
* Someone on YouTube is objecting because Aston Villa football club will need to find a new practice ground.
But let's not say "teachers for education, doctors for medicine, non-specific professionals for the railway.". They are not equal.
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