Common passing loop for Up and Down lines

[beast66606]

Stowmarket loop was made bi-di when Colchester PSB took over in the mid 1980s but like others, it's off to one side, not down the middle.

[EddieB]

Something similar was installed at Kensington Olympia, when reduced from four tracks to three.  Although signalled bi-directionally, in practice the centre road tends to be a passing loop for northbound through trains most commonly.

[caradoc]

3 hours ago, The Stationmaster said:

In the more recent Reading alterations things were changed again and the Down Loop (relaid at long last) became the Down Relief while the Down Relief became the new passenger loop (which I have actually travelled over in a passenger train on one occasion).  Thus the Down Relief is back where it was prior to February 1961 and what was the Up Relief back then is now the site of the current passenger loop.

 

Thanks Stationmaster, I knew there had been a re-arrangement but didn't remember it entirely correctly ! 

 

[The Stationmaster]

2 hours ago, Mike_Walker said:

I'm not sure this correct.  I've reviewed the NR Scheme Plans for the Reading project (I prepare train crew route diagrams for GWR and other TOCs) which make no reference to altering the alignments of Relief lines and Loop at any stage during the project only alterations to the signalling and designations.  On scheme plans, new works are shown in red, items to be recovered in green and unaltered remains black.  On all stages the lines in question are shown in black and, personally, I don't recall the present layout being changed at any time during the works.

 

Regarding the Slough - Iver area back in 2014 Mark Hopwood and I drew up a scheme to provide a 5 track passenger railway all the way from Farnham Road (west of Slough) all the way to Hanwell Bridge Junction.  The additional line would have been on the Up or north side and would require considerable rebuilding of all the stations and many bridges although replacing the Wharncliffe Viaduct was seen as a step too far!  The idea was to provide additional capacity to accommodate Crossrail and would make the present Up Relief bi-directional  with "tidal flow" operations, used for Up trains in the morning peak, Down in the evening.  It was submitted to NR by GWR as part of bids for CP6 but failed to fly.

 

It is  correct although sorry I forgot to mention that the position of the Goods Loop had been swopped to the centre before the most recent Reading works (presumably to avoid relaying costs?), but it remained a goods loop with slow speed connections.  What happened with the recent Reading scheme change altered it considerably as the eastern end with the Down Relief realigned further to the east of the orriginal connection into the loopconnection moved much nearer to the site of Sonning sidings, presumably to improve the geometry of the entry connection at that end.

 

Incidentally the tidal flow 5 tracking was looked at back in the 1980s in connection with the Heathrow Link although the idea then was an additional running line on the south side and east of what became Airport Jcn but it was very rapidly dismissed because of what it was going to cost (and that was before estimates were sought ).  The next occasion it was looked at - apart from the proposals mentioned by Olddudders and myself - was in connection with one of the early ideas for what became 'Heathrow Connect' service when it was proposed to operate it from St Pancras with a flying junction at Acton.  It would be relatively easy - albeit with widening the formation into the cutting sides and with a lot of slewing in some places to keep up line speeds  - to add one or two additional running lines westwards from there apart from the bottleneck through Ealing Broadway and then through Hanwell station onto Wharncliffe Viaduct.  Beyond the latter and on to Airport Jcn the only real problems would be the stations at Southall and Hayes plus the two overbridges.  Those  apart a land footprint wide enough for 6 tracks existed almost throughout from Hanwell Bridge to beyond Dawley and in fact the there had of course long been 5 or 6 running lines over that distance apart from through the two stations.

[The Stationmaster]

3 hours ago, Harlequin said:

Could the central siding of the type described have been used to allow passing by having the train ahead setting back into it, assuming it was not used to hold rolling stock?

 

(BTW: A bi-directional central loop, as the OP imagines it, would need facing points at both ends, signalling and multiple FPLs so quite a complex and expensive bit of infrastructure. In fact, quite expensive in terms of space in a model too...)

 

Phil generally the middle sidings were too short to hold all but a short train although in some cases - Bath is again an example I think - they might be used to transfer empty arriving trains off one line to the other side of the station. ready to depart towards whence they had come.  The middle siding at Neath was slightly more  interesting as it extended east of the station but again it only had trailing connections to access it.

 

I can't think of any long enough to be used to recess a freight train to allow overtaking although it is possible that if we go a long way back one might have been used to shunt the stock of a local passenger train to allow another train to pass.  But all the photos I have seen of these sidings back in the past seem to show them occupied by various loose vehicles and in some cases by a pilot engine.  The Bath one seemd popular with photographers for some reason.

 

I think the nearest we can get to a bi-directional line might be the middle line at truro - originally the Up Branch and since 1971 the Up Main, i It was only signalled in the Up direction for through trains but a train arriving from the west in the Up direction could reverse on that line before heading back to the west.  so hardly meeting the OP's remit but a bit more interesting than the run of the mill.  

[Grovenor]

Here is the local control panel and one of the signals at a bi-di central loop at Les Arcs in the Midi.

SNCF 1968. The right track formation if the wrong place.