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How to create a SP linespeed?
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Eccles1983
On Moderation
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Signals repostioned is the first one. Braking distances change.
Track maintenance schedules and depth needs looking at.
Paperwork wise? No idea.
Track maintenance schedules and depth needs looking at.
Paperwork wise? No idea.
civ-eng-jim
Member
If it's a hypothetical line then the following list will provide a plethora of constraints which determine line speed:
https://www.railforums.co.uk/threads/permanent-way-question-upgrading.176400/#post-3823680
I don't know the criteria which allows Sprinters to go faster over (presumably) loco hauled trains. Better axle load spread? Better braking?
https://www.railforums.co.uk/threads/permanent-way-question-upgrading.176400/#post-3823680
I don't know the criteria which allows Sprinters to go faster over (presumably) loco hauled trains. Better axle load spread? Better braking?
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I was thinking of the Leeds-Harrogate line, that was resignalled in 2013, as class 170s are struggling in first gear at 60mph.
The line was broken up into smaller sections for increased capacity, better signal sighting for 75 mph and conversion of the only level crossing from manual to automatic under CCTV. Curvature would allow 75mph on most of the route but according to Network Rail no one has asked for an increase in speed.
Bullhead rail was gradually replaced in the 1970s with cwr on concrete sleepers and deep ballasting except for a short section between Horsforth and Headingley on both lines which is still jointed track.
The siding and crossing complex on a curve at Horsforth was repositioned slightly and relayed in 2013 increasing speed from 45 to 60mph for non-stopping trains but not many drivers observed this restriction in the Down direction as it was on a gradient climbing out of Leeds where they were just attaining 60mph and didn't want to brake down to 45mph and then have to accelerate up to 60 again. Deltic+8 on the KX-Harrogates were the worst where I have timed them doing excess of 60mph here and in excess of 80mph at the bottom of Bramhope Tunnel riding quite smoothly in a Mark 2d coach.
from a signalling point of view:
Network change, needs obtaining, a speed increase might create a detriment to other operator so all operators need to agree, this is a consulation process and has been know to take years, Network Rail standard 30021 is the linespeed paperwork, a scheme plans needs approval, substantiated with braking calculations, effective TPWS and any relevant risk assessments, all signage needs sighting, probably by committee, signal spacing may need altering so you'll need civils design for foundations, after ground investigation, foundation design, structure design, signalling wiring alterations, distruptive access, a commissioning event involving most likely a shut down, removal of any redundant signals, new cabling etc..
not that simple, and I haven't mentioned track, condition, cant or maintenance regime.
Network change, needs obtaining, a speed increase might create a detriment to other operator so all operators need to agree, this is a consulation process and has been know to take years, Network Rail standard 30021 is the linespeed paperwork, a scheme plans needs approval, substantiated with braking calculations, effective TPWS and any relevant risk assessments, all signage needs sighting, probably by committee, signal spacing may need altering so you'll need civils design for foundations, after ground investigation, foundation design, structure design, signalling wiring alterations, distruptive access, a commissioning event involving most likely a shut down, removal of any redundant signals, new cabling etc..
not that simple, and I haven't mentioned track, condition, cant or maintenance regime.
edwin_m
Veteran Member
All SP trains that can exceed 75mph have disc brakes, so I believe their better braking means there is no need to re-position signals at least up to SP90 (are there any higher SP speeds signed?). I'd guess the main thing would be to check the track, structures and earthworks for the extra forces (which may not be that much more than those of freight trains at existing speeds).
hexagon789
Veteran Member
As SP speeds apply to 170s in the Scotland Sectional appendix (not sure about other regions), I believe there may be an SP 100 somewhere in Scotland iirc.
Either than or I'm misremembering and it's an HST differential.
Joseph_Locke
Established Member
SP was originally a BR fiddle to allow the then-new Sprinters with the new (and novel, for BR trains) air suspensions to run at higher speeds because their lower track loading meant the effective track tonnage reduced, meaning the track category remained constant. Effectively, it got round the need to do a lot of track renewal that would have otherwise been required. Other than that their very low RA (as a class - 2?) means no bridgeworks, so provided you have compliant signal braking to Appendix C, compliant sighting distances and you keep the cant deficiency within exceptional you're good to go.
The rub (until about 6 months ago) was that no-one knew the actual definition of a Sprinter was, other than 15x ...
The rub (until about 6 months ago) was that no-one knew the actual definition of a Sprinter was, other than 15x ...
Class 170101
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SP speeds also apply in Anglia though I'm not aware of any SP100 speeds here.
NR tried to reject 170s from Sprinter speeds over 75 at one time.
hexagon789
Veteran Member
I know they've got some SP90, but agreed - can't think of any SP100 in Anglia.
paul1609
Established Member
In the investment starved south we dream of 60mph, 171s struggle with the 40 mph linespeed between Doleham and Ore.
Kingspanner
Member
I'm not rising to that bait.
Level crossings are a particular issue. They all need reassessing for risk and sighting time. If the risk goes up (and it will), mitigation needs to be proposed, where practical. Between Leeds and Harrogate there are 7 crossings.
Another issue when going above 60mph is that the track maintenance standard requires an increase in patrolling. Extra cost of course. As others have said signal spacing shouldn’t be an issue, but signal sighting may well be. TPWS would all need recalculating and probably moving. All signals capable of displaying a stop aspect would have to be reassessed for SPAD risk. These take about half a day each.
And the big thing is what is underneath the sleepers. Any structures, culverts and embankments would need to be checked and potentially reassessed if marginal. And possibly strengthened.
Then there’s about 80 other factors, some of which won’t apply in this example.
Another issue when going above 60mph is that the track maintenance standard requires an increase in patrolling. Extra cost of course. As others have said signal spacing shouldn’t be an issue, but signal sighting may well be. TPWS would all need recalculating and probably moving. All signals capable of displaying a stop aspect would have to be reassessed for SPAD risk. These take about half a day each.
And the big thing is what is underneath the sleepers. Any structures, culverts and embankments would need to be checked and potentially reassessed if marginal. And possibly strengthened.
Then there’s about 80 other factors, some of which won’t apply in this example.
As I said earlier, there is only one level crossing, at Huby, not seven. As the line was resignalled for 75 mph I assume everything is hunky-dory as far as braking and sighting distances are concerned and undertrack structures. Speed limit just hasn't been implemented after six years.
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Randomer
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I assume that the seven crossings include foot crossings rather than the single level crossing you are thinking of.
There’s 7 level crossings. Look at the map.
https://www.networkrail.co.uk/communities/safety-in-the-community/level-crossing-safety/
Ah, really useful map. You are talking foot crossings, I was meaning vehicle crossing at North Rigton with proper barriers. There is always something to bugger up a good idea. I will have to look more closely the next time I travel to Leeds.
Wouldn't this be addressed by repositioning the W boards when resignalling was done for higher speed?
edwin_m
Veteran Member
Each crossing would have to be risk-assessed. As the trains are faster there is clearly going to be more risk, and recent experience suggests this will trigger at least one expensive risk mitigation measure.
dk1
Veteran Member
I was told that going that extra 10mph from 90-100 is much more costly in many ways & the reason regional routes often never make those magic 3 figures.
Footpath / accommodation level crossings are usually more troublesome than highways particularly where highway crossings are already full barriers. The latter generally have the highest standard of protection available, and therefore even if the risk goes up it can usually be demonstrated that there is no ‘reasonably practical’ alternative, and the increased risk can be within limits.
For footpath crossings there are potentially dozens of mitigations possible to mitigate increases in risk, ranges no from the relatively minor up to providing a footbridge. Because the costs to mitigate the risk are much lower (even with a footbridge), it then can easily be ‘reasonably practical’ to do something, and therefore something must be done.
Whistleboards is an interesting point. If they are moved out more than 400metres from the crossing they are deemed to be ineffective. And in any event, if the crossing is shown to be used in the night time quiet period the the whistleboard cannot be relied upon and alternative mitigations need to be considered.
edwin_m
Veteran Member
I'm aware of one line where a proposed increase in train numbers from "lightly used" to "moderately used" is triggering an unacceptable risk score at a CCTV crossing.
It’s possible, of course.
It may not just be train numbers, but the number of people on board. If, say, the service doubles in frequency, and the number of people using the line also doubles, the risk will rise by much more than double.
hexagon789
Veteran Member
Especially as you need a fair distance for it to make much of a time saving anyway.
4 seconds a mile at best.
Presumably the "with paperwork" aspect includes a piece of paper on which someone has estimated by how much journey times could be reduced, passenger journeys could be increased and revenue increased. Preferably this bit of paperwork being done and considered before rousing the techy people. Perhaps this happened with the Harrogate line
hexagon789
Veteran Member
Sometimes it seems to be more advanced vanity project - boasting of 100mph running, than actually having a time benefit. Likely why it's not generally done now unless it gives a benefit.
hexagon789
Veteran Member
I hoped the techy people had been consulted before the line was resignalled specifically for an increase in speed and capacity. If not why site signals for an increase in speed?
Assuming that it has been signalled for 75mph, the signalling Engineers would clearly have been involved. That doesn’t mean that all the relevant engineers would have been.
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