Track Singling Benefits

[Bletchleyite]

The Island line is a good argument for further singling. The placement of the loops combined with rolling stock being withdrawn due to age has caused an odd 40 minutely timetable. The line would be better served by 2 x 3 coach 230s (with longitudinal seating in the middle coach to allow more standing during high demand). A single line with one loop in the middle would also allow the steam railway to extend to Ryde St Johns.

While the verdict on it has been delayed, I think there is a very good chance that this is precisely what is going to be proposed for it by SWR.

 

[Nippy]

Would 230s get through the tunnel at Ryde?

 

[Bletchleyite]

Would 230s get through the tunnel at Ryde?

See the 230 thread or the Island Line one for more, but yes, they do fit since the beams in the tunnel were replaced for new, thinner ones, which has increased headroom in the tunnel from what it was to a mainline height (though short vehicles are required due to the switchback curves, which the 230s of course are at 18m long).

 

[Chester1]

Would it not be better just to insert the loop in the optimum place, and retain the others in case of disruption etc ?

A line that is completely segregated from the network and has reliable rolling stock should not have much disruption. Three stretches of double track would have extra maintenance and replacement costs compared with one. Handing over one track between Smallbrook Junction and Ryde St Johns to IWSR would offer economic benefits for the area. I think that despite having twin portals its actually only one tunnel. It could be possible to slew a single track down the middle to allow slightly longer coaches to run through the sharp curves.

The line requires a big opperating subsidy and needs a large investment to keep running in the near future. A half hourly three coach service would be an improvement on the current service and while below historic frequencies would be more than adequate. I know all 230s ordered so far have been 2 or 3 coaches but I wonder if there would be an issue with adding a second intermediate coach if usage surged?

Edit - just realised that I have gone off topic, but the Island Line is a good example of when singling a line could be a good idea.

 

[Legolash2o]

Really? The benefit of turning a little used line into a single should be obvious, surely. I am not trying to be difficult but rather obviously the main driver is to save money through reduced maintenance and replacement costs.

When times are hard such a decision may be the difference between a service and no service at all

Money and maintenance was the first thing that came to mind. I was just wondering if there was anything other reasons and how it would impact capacity on the line.

 

[61653 HTAFC]

There was some singling of the Robin Hood Line to make space for Nottingham tram. Must have been around 2000 which I think is later than any of the "most recents" suggested.

That one is notable also because the previous double track had only been re-opened around a decade earlier!

Re: the user who suggested retaining excess loops on Island line, I can see how this would be useful if one of the trains was running 15mins late, the one that's on time could continue to the next loop rather than also being delayed. This is something that frequently happens on the Penistone Line: if the down service is late to Penistone, it'll be held there until the up service gets in, rather than crossing at the next loop at Shepley. The downside is that you still need to maintain the pointwork even if it only operates once a blue moon... otherwise you end up like the Heart of Wales line was a few years back, where only those loops which were timetabled for trains to meet were in working order. The other loops had had parts robbed to keep the main ones going, meaning any disruption had a greater impact, and that charters were tough to plan and path.

 

[Chester1]

That one is notable also because the previous double track had only been re-opened around a decade earlier!

Re: the user who suggested retaining excess loops on Island line, I can see how this would be useful if one of the trains was running 15mins late, the one that's on time could continue to the next loop rather than also being delayed. This is something that frequently happens on the Penistone Line: if the down service is late to Penistone, it'll be held there until the up service gets in, rather than crossing at the next loop at Shepley. The downside is that you still need to maintain the pointwork even if it only operates once a blue moon... otherwise you end up like the Heart of Wales line was a few years back, where only those loops which were timetabled for trains to meet were in working order. The other loops had had parts robbed to keep the main ones going, meaning any disruption had a greater impact, and that charters were tough to plan and path.

The difference between the Island Line and other lines with single sections is interaction with other networks. Why would an 230 on the Island Line run 15 minutes late? Even with battery charging at one end there would still be about 8 minutes recovery time per hour with more possible if the range was sufficient for two return journeys. Single track loops are a balance between cost and capacity / reliability. Single branch lines that can support a decent frequency with sufficient recovery time do not need loops. Single track sections on popular longer line like the WofE line are a different matter.

 

[61653 HTAFC]

The difference between the Island Line and other lines with single sections is interaction with other networks. Why would an 230 on the Island Line run 15 minutes late? Even with battery charging at one end there would still be about 8 minutes recovery time per hour with more possible if the range was sufficient for two return journeys. Single track loops are a balance between cost and capacity / reliability. Single branch lines that can support a decent frequency with sufficient recovery time do not need loops. Single track sections on popular longer line like the WofE line are a different matter.

It's isolated from the rest of the rail network, but it doesn't operate in a bubble as it connects with ferries which connect with trains on the mainland. There's all sorts of reasons a service could be delayed by 15mins (a minor fault that needs fixing, or being held for a delayed ferry are just two examples).

Though as you say it is a balance to be struck between cost and flexibility... I said as much in the post you quoted.

 

[satisnek]

Ledbury-Hereford was in about 1990 I think (coupled with a speed reduction to 65mph - it used to be 90).

It was earlier than that - 1984??

As for the Island Line, this was a singling too far. The Ventnor line was originally built as single track south of Smallbrook Junction, with passing loops at Brading, Sandown, Shanklin and Wroxall. The Southern Railway doubled the Brading-Sandown section in the 1920s, in order to increase capacity. This was retained with the Ryde-Shanklin electrification until the late 1980s when BR not only saw fit to revert to single track, but removed the loop at Brading as well, thereby making a half-hourly service impossible.

Surely the best option would be reinstate the double track (in effect, with modern signalling, extending the Sandown loop), rather than laying a loop at Brading, which would require two additional turnouts?

 

[Mordac]

It was earlier than that - 1984??

As for the Island Line, this was a singling too far. The Ventnor line was originally built as single track south of Smallbrook Junction, with passing loops at Brading, Sandown, Shanklin and Wroxall. The Southern Railway doubled the Brading-Sandown section in the 1920s, in order to increase capacity. This was retained with the Ryde-Shanklin electrification until the late 1980s when BR not only saw fit to revert to single track, but removed the loop at Brading as well, thereby making a half-hourly service impossible.

Surely the best option would be reinstate the double track (in effect, with modern signalling, extending the Sandown loop), rather than laying a loop at Brading, which would require two additional turnouts?

Thinking this would be a great place to trial that reduced-spec ERTMS Regional variant: captive stock, isolated line, needs cost reduction..

 

[Bletchleyite]

Thinking this would be a great place to trial that reduced-spec ERTMS Regional variant: captive stock, isolated line, needs cost reduction..

No need for any of that, train staff and ticket would work fine, and the ticket would only be needed for the last evening train.

 

[ac6000cw]

No need for any of that, train staff and ticket would work fine, and the ticket would only be needed for the last evening train.

Quite - you really don't need a lot of complicated infrastructure just to run a few trains on a very simple system.

 

[Cambridgejcn]

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

Littleport-Downham Market was singled on 17 June 1984, Magdalen Road (Watlington)-King's Lynn Junction was singled on 10 February 1985. Single leads from both King's Lynn and Norwich lines were introduced at Ely North Junction on 11 May 1992. Only the latter works at Ely were associated with the electrification scheme, which came into operation fully on 24 August 1992 (class 317 emus having progressively taken over dmu diagrams on 22 August).