Track Singling Benefits

[Legolash2o]

Following from the topic below, why do they single track when it's already doubled? What's the benefit?

https://www.railforums.co.uk/threads/singling-a-line.177866/

 

[furnessvale]

Without the complications of a viaduct, singling is normally considered when one line falls due for renewal which causes a spike in maintenance costs.

 

[pdeaves]

What's the benefit?

Primarily financial. There is less equipment to maintain so general upkeep costs less, whether parts requirement or number of staff 'on the books'.

 

[edwin_m]

It may also be possible to increase the speed a bit by slewing the single line across the formation to make a sort of racing line for curves.

 

[LNW-GW Joint]

Singling is usually accompanied by drastic simplification of the signalling.
It also simplifies the junctions at each end (eg single instead of double turnouts, with fewer point ends and signals).
It was often done in association with area resignalling, and massively reduces the operational cost of the line with the closure of multiple local signal boxes.
It will also reduce the capital and installation cost of the new signalling equipment.
All part of the "value engineering" of modernisation schemes.
Except that many of these BR schemes are now being reversed to cope with extra traffic...

 

[Brush 4]

Just short termism. BR reduced the capacity to the low level it had become after reduction in services, closure of feeder lines and closure of goods yards/depots. By so doing, it ensured that future expansion could not be handled and, so it has proved, with redoubling necessary at Cotswold, Chiltern, and parts of Salisbury-Exeter, with more doubling planned. Reopening Scottish and Welsh branches also . For some of the Scottish and Welsh lines reduced to freight only, the traffic disappeared as the industry did, ironically allowing reinstatement of passenger services.

 

[Altfish]

Singling is usually accompanied by drastic simplification of the signalling.

Surely it is more complicated; if you have two lines (One for each direction) don't you need less signalling?
Or am I being dumb?

 

[cle]

An interesting pro-active singling was some of the Victoria Regional Rail in Australia, where they actively singled within a big-bang of investment to straighten out (bridge clearance) and for line speeds - now of course capacity-wise, there has been a boom in regional rail travel out of Melbourne and they're looking at redoubling certain stretches (Ballarat or Bendigo line, can't recall) within 10 years of singling it.

 

[LNW-GW Joint]

Surely it is more complicated; if you have two lines (One for each direction) don't you need less signalling?
Or am I being dumb?

Well, in the areas I am familiar with (Cotswold and Ledbury-Hereford), singling took out most of the intermediate signal boxes which were by then not controlling any sidings or junctions.
At Worcester one of the boxes on the triangle was eliminated, and more recently several boxes west of Ledbury were eliminated.
Longer signal sections was another bi-product of the down-sizing.
Yes you need more controls for bi-di working, but in a modern box it can all be done centrally on a single screen.
Worcester was actually left in a very odd state with the old kit mostly retained - it's still waiting to be swept away with new signalling from the West Midlands SCC.

 

[Lucan]

singling took out most of the intermediate signal boxes

Why do we need intermediate signal boxes these days anyway? You don't need singling for that.

 

[yorksrob]

Singling was done almost always as an economy measure. Being able to slew the track for faster journeys tended to be a happy bi-product.

Interesting exceptions were the tunnels on the Tonbridge - Hastings line. They were double track tunnels built by cowboy builders with too few layers of brick.

The additional layers were built in and as a result, the tunnels were narrower than the standard loading gague, until 1986, when the line through the tunnels was singled, and ordinary width rolling stock could be used.

 

[Ianno87]

Out of interest, what was the last line on the GB network to be singled?

 

[MadMac]

In Scotland, I can't think of one after the Milngavie branch.

 

[30907]

Out of interest, what was the last line on the GB network to be singled?

Possibly Uckfield and/or Ashford-Hastings. Other regions were quicker off the mark.
Problems of capacity are recent (following the move to "little and often" patterns of service post Sprinterisation/Privatisation - delete according to political taste!).

 

[AndrewE]

Without the complications of a viaduct, singling is normally considered when one line falls due for renewal which causes a spike in maintenance costs.

Exactly. Short-term thinking at its worst, as the single line wears out at twice the rate, plus you have extra points at each end to maintain and replace on a regular basis. Not to mention the impacts on reliability (on a timetable that has already been shoe-horned into the single track bit.)

Why do we need intermediate signal boxes these days anyway? You don't need singling for that.

Further short-sighted economies, thus ensuring that on a single line 2 trains can't follow each other on the single line. Track-circuit block allows lots of block sections and more trains and I think it is compatible with single-track.... Doing this is called "flighting" and was how BR proposed to operate its initial single-bore channel tunnel, half a dozen trains alternately in each direction.

 

[Bald Rick]

It was almost always to save money in the short to medium term. BR was under intense cash pressure, and had what today would be called ‘unconventional’ methods of accounting. When stretches of track came up for renewal, it was (obviously) cheaper to lift one and not have to put it back. The signalling alterations were almost done for ‘free’ as design was counted as a overhead, and the implementation was often done by the local chaps, mostly in spare time. The maintenance savings came through immediately, as it halved patrolling costs, which is the main maintenance cost on lightly used lines. The fact that traffic ’doubled’ on the remaining track rarely affected that, as even with the doubling the traffic was below the threshold for raising patrolling levels. And, often, the service was reduced at the same time anyway.

Now you can say it was short termist, but how short term is short term? Some of the singling was done well over 50 years ago, and has saved at least two renewal cycles. Whilst some of the singlings have had to be undone in the last 20 years, it is pretty plain that the majority of them have not needed to be done and the savings continue.

Final point - sometimes the singling was done to make electrification cheaper. I have a feeling that some of the Kings Lynn line was singled at electrification - that’s 27 years ago now.

 

[ac6000cw]

Out of interest, what was the last line on the GB network to be singled?

Ely - King's Lynn was partially singled on electrification between 1989 - 1992, so that might be a contender?

 

[Chester1]

It was almost always to save money in the short to medium term. BR was under intense cash pressure, and had what today would be called ‘unconventional’ methods of accounting. When stretches of track came up for renewal, it was (obviously) cheaper to lift one and not have to put it back. The signalling alterations were almost done for ‘free’ as design was counted as a overhead, and the implementation was often done by the local chaps, mostly in spare time. The maintenance savings came through immediately, as it halved patrolling costs, which is the main maintenance cost on lightly used lines. The fact that traffic ’doubled’ on the remaining track rarely affected that, as even with the doubling the traffic was below the threshold for raising patrolling levels. And, often, the service was reduced at the same time anyway.

Now you can say it was short termist, but how short term is short term? Some of the singling was done well over 50 years ago, and has saved at least two renewal cycles. Whilst some of the singlings have had to be undone in the last 20 years, it is pretty plain that the majority of them have not needed to be done and the savings continue.

Final point - sometimes the singling was done to make electrification cheaper. I have a feeling that some of the Kings Lynn line was singled at electrification - that’s 27 years ago now.

Every mile of track is sacred...!

I agree if a single section has been sufficient for decades but needs redoubling now then even with the benefit of hindsight it was not a bad decision. Some single sections like Dore are a major problem and redoubling is necessary. The Windermere branch is a good example of a singling that was probably a good idea. Id say it needs longer platforms and either electrification or battery / hydrogen trial much more than redoubling.

 

[yorksrob]

Possibly Uckfield and/or Ashford-Hastings. Other regions were quicker off the mark.
Problems of capacity are recent (following the move to "little and often" patterns of service post Sprinterisation/Privatisation - delete according to political taste!).

I think the Marshlink was around 1979/80.

 

[yorksrob]

Singling was definitely a better option than the ultimate calamity of closure.

 

[30907]

Ely - King's Lynn was partially singled on electrification between 1989 - 1992, so that might be a contender?

Uckfield was 1990, so Lynn is possibly the latest.

 

[Chester1]

Singling was definitely a better option than the ultimate calamity of closure.

Agreed. The same is true of reopenings. Its better to get them done as a basic single track railway than insist upon double tracking etc and make the cost too high. I have never understood why people think the Borders Railway should have been / should be double track, it needs a couple of miles extra double tracking to make the timetable reliable.

 

[61653 HTAFC]

Not quite as recent as Ely to Lynn, but Huddersfield to Clayton West Junction remained double track until around 1988, despite the Clayton West branch being closed (with subsequent loss of freight traffic) in 1983. At the time the line had an hourly service at best, with many gaps and little or no Sunday service, so it probably made sense (Berry Brow station would've been more than double the cost had it needed 2 platforms and a bridge) but I'm convinced that with the current service levels (now hourly with the odd extra) demand is significantly suppressed... particularly from the quite prosperous areas of Brockholes, Shepley and Denby Dale.

 

[furnessvale]

Singling was definitely a better option than the ultimate calamity of closure.

Very true, and you only need to look at the USA to see what volume of freight, or Switzerland for passengers, can be put over a single line, PROVIDED the timetable is robust.

George

 

[ac6000cw]

It was almost always to save money in the short to medium term. BR was under intense cash pressure, and had what today would be called ‘unconventional’ methods of accounting. When stretches of track came up for renewal, it was (obviously) cheaper to lift one and not have to put it back. The signalling alterations were almost done for ‘free’ as design was counted as a overhead, and the implementation was often done by the local chaps, mostly in spare time. The maintenance savings came through immediately, as it halved patrolling costs, which is the main maintenance cost on lightly used lines. The fact that traffic ’doubled’ on the remaining track rarely affected that, as even with the doubling the traffic was below the threshold for raising patrolling levels. And, often, the service was reduced at the same time anyway.

Now you can say it was short termist, but how short term is short term? Some of the singling was done well over 50 years ago, and has saved at least two renewal cycles. Whilst some of the singlings have had to be undone in the last 20 years, it is pretty plain that the majority of them have not needed to be done and the savings continue.

Final point - sometimes the singling was done to make electrification cheaper. I have a feeling that some of the Kings Lynn line was singled at electrification - that’s 27 years ago now.

I'm entirely with you on this one. My nearest local line (Cambridge - Newmarket) was singled in 1983, at the time of the Cambridge area re-signalling, and still has spare capacity despite the passenger service frequency having been doubled in the meantime. The singling was done by joining together the best bits of the two tracks (which was pretty old stuff anyway) and lifting the rest - that put off serious track renewals for about 20 years (the oldest parts were eventually relaid with CWR on steel sleepers in Railtrack days). So that's 35 years and counting of reduced costs - money better spent elsewhere on the network...and in any case, the capacity limitations are as much with the lines it connects to at each end as on that section of route itself.

 

[yorksrob]

Agreed. The same is true of reopenings. Its better to get them done as a basic single track railway than insist upon double tracking etc and make the cost too high. I have never understood why people think the Borders Railway should have been / should be double track, it needs a couple of miles extra double tracking to make the timetable reliable.

Yes indeed. I'd rather see a line put back as single track, than wait forever for double track to become affordable.

Very true, and you only need to look at the USA to see what volume of freight, or Switzerland for passengers, can be put over a single line, PROVIDED the timetable is robust.

George

Yes, the mainline west of Salisbury strikes me as one where they get a lot out of the single track infrastructure.

 

[Dr_Paul]

Out of interest, what was the last line on the GB network to be singled?

Perhaps Wimbledon station, when the Croydon Tram took over platform 10, and the Sutton line restricted to the now bi-directional platform 9.

 

[Tomnick]

Further short-sighted economies, thus ensuring that on a single line 2 trains can't follow each other on the single line. Track-circuit block allows lots of block sections and more trains and I think it is compatible with single-track.... Doing this is called "flighting" and was how BR proposed to operate its initial single-bore channel tunnel, half a dozen trains alternately in each direction.

You don’t need intermediate signal boxes to achieve that though. If the single line’s track circuited throughout, automatic signals to break the section as required would suffice.

 

[AndrewE]

You don’t need intermediate signal boxes to achieve that though. If the single line’s track circuited throughout, automatic signals to break the section as required would suffice.

I thought that was what I said - it's what I meant anyway. You don't need signal boxes for Track Circuit Block and it's a shame that singling wasn't balanced by the reduction in the length of signal sections. In fact I think there are a lot of lines (even double track lines) where capacity could be increased by cutting headways for relatively little cost. Crewe to Chester? I don't know whether this level of detail is in the public domain though, the Sectional appendix shows the signalling type but not signal or section length/frequency IIRC.

 

[Bald Rick]

I thought that was what I said - it's what I meant anyway. You don't need signal boxes for Track Circuit Block and it's a shame that singling wasn't balanced by the reduction in the length of signal sections. In fact I think there are a lot of lines (even double track lines) where capacity could be increased by cutting headways for relatively little cost. Crewe to Chester? I don't know whether this level of detail is in the public domain though, the Sectional appendix shows the signalling type but not signal or section length/frequency IIRC.

The Tran Planning Rules show the minimum headway permitted. You can find them here: http://archive.nr.co.uk/browse documents/Rules Of The Route/Viewable copy/roprhome.pdf

(Big file to download though)