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Author Topic: Two Tracks Now? - the line from Chippenham to Trowbridge  (Read 3399 times)
grahame
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« on: November 29, 2018, 02:55:58 pm »

Its now a case for Two Track Now for Melksham, I notice on opentraintimes that it only has a single line and platform, I suppose the problem is that there would be the cost of an extra platform and footbridge and a shelter.

Looking back five or more years ago, until fifty years ago, the single remaining line through Melksham was adequate for the number of trains that were running / were wanted to be run.  A sleepy backwater after April 1966 when the local service was withdrawn, a single line that took just under 20 minutes to traverse without intermediate signals was plenty enough, and indeed the occasional train could be held on the single line waiting for a slot on the London to Bristol main line at one end, and the main line that people forgot (Cardiff to Portsmouth) at the other.

A re-opened station at Melksham from 1985 provided for a commuter service to Swindon and back, and was well within the single line capacity, as were a handful of additional trains tried from time to time.  But the additional trains died back each time - I would suggest due to a lack of marketing (few people knew of them), a lack of frequency (if there was an oubound train when you wanted one, there probaby wasn't a return when you wanted it) and a lack of reliabiity (always the first to be cancelled; joke about trains being held together with sticky tape).

Fast forward to 2013.  On 7th December, there were 5 train movements along the line through Melksham. On 8th December there were 53.  What had happened?

A local campaign with Coffee Shop members Txxxxxx, Lxx, Rxxxxxxx amongst others in strong support, had lead to funding being found for a three year trial of a service which the team involved believed would be of sufficient of a level to cvercome the issue of a lack of return trains.  Also on that day, the main line from Westbury to Reading via Newbury was closed, and London to the West Country expresses were diverted alomh the single track. 

53 services is exceptional, but with 18 "TransWilts train" paths, and lots more freight services too, the line today is pretty busy.  In fact today ... there are 35 paths on real time trains. Some of them are alternatives, some run as required.  But it's a typical day and perhaps 30 trains will have passed or stopped at Melksham's platform today.   Critically for service reliabiity, not all ar on time.  A train that was due to pass ot 02:43 didn't make it until 05:21, an conversely there was a through train running 12 minutes early.  In time when services were few and far between, late running was rarely a problem to other trains, but these days a late train in one direction is likely to be reflected back in the form of a late train the other way ... and that second train waiting for the single line can't be sidetracked at either Chippenham or Trowbridge - so may have to wait on (and disrupt) the main line.

At present, it copes.  And it could cope with a handful of extra trips too.  A service from Swindon at about 07:50, returning from Westbury at 08:40.  A service from Swindon at about 16:30 returing from Westbury at around 17:20, and a service from Westbury at around 21:30 returning from Swindon at around 22:40 should fit and would fill major timetable gaps.  But take it up to hourly (which it really needs) and add in all the extra freight we're expecting once HS2 track sections from Westbury start travelling up to site, with spoil / landifll trains headed in the opposite direction, and you have an issue - even if you can shoehorn more into the timetable, you have a reliabiity / robustness issue when something presents out of order - and nowhere for slower trains to be sidetracked along the way - once they have left Westbury, there is just plain line to Swindon and vice versa.

So - what to do?

Requsts / campaigns do double track are tempting.  But they don't solve the bypass problem of a faster passenger train needing to get past a slower freight, and they are relatively expensive - especially in terms of putting in a second platform, and footbridge with ramps or lifts at Melksham.  Passenger number at Melksham have now risen enough for us to be provided with just a "Polesworth Solution" - a single platform with trains calling only in one direction.  But never the less, an expensive solution to most but not all of the issues.

Suggestions have been made to add an intermediate signal on the single line to allow 2 trains to follow each other - a headway of perhaps 11 minutes rather than 18. And, yes, that could help somewhat - but perhaps only somewhat and we would only end up with another ceiling in a few years time. Timetabling would be interesting, with 'flights' of trains in each direction to make an use of the xtended capacity.

To me, the most attractive solutions are based on passing loop(s) away from the Melksham platform.  Preferably as long as possible so that they can dymanically allow trains to pass while underway - timetabled hourly locals to pass mid-loop.  And, please, bidirectioanlly signalled so that trains can overtake too. While you are re-doing the signalling, please don't limit it like it is at present - please allow trains to be reversed at Melksham in the future.

Passing loops that reduce again to single tracks near the juctions will also save significant issues at Thigley (were the cant on the through lines gives a problem with a traditional double jucntion) and near Staverton (where the bridge over the Avon is only single track width.
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SandTEngineer
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« Reply #1 on: November 29, 2018, 03:18:32 pm »

Think you mean the 'Penryn Solution'.... Roll Eyes https://en.m.wikipedia.org/wiki/Penryn_railway_station
« Last Edit: November 29, 2018, 03:25:15 pm by SandTEngineer » Logged

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grahame
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« Reply #2 on: November 29, 2018, 03:31:23 pm »

Think you mean the 'Penryn Solution'.... Roll Eyes https://en.m.wikipedia.org/wiki/Penryn_railway_station

It's very much in there as a sub-option ... one of the loops coming close enough in to Melksham to have a platform extension on the end of it.
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brooklea
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« Reply #3 on: November 29, 2018, 04:55:17 pm »

While you are re-doing the signalling, please don't limit it like it is at present - please allow trains to be reversed at Melksham in the future.
Trains can reverse at Melksham now.
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Red Squirrel
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« Reply #4 on: November 29, 2018, 04:55:59 pm »

Think you mean the 'Penryn Solution'.... Roll Eyes https://en.m.wikipedia.org/wiki/Penryn_railway_station

Fiendishly clever, these S&T Engineers...

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grahame
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« Reply #5 on: November 29, 2018, 05:17:56 pm »

While you are re-doing the signalling, please don't limit it like it is at present - please allow trains to be reversed at Melksham in the future.
Trains can reverse at Melksham now.

??   Not sure they can being in the middle of the single line section between the axle counters.  On 2nd / 3rd Jan, the 06:10 from Swindon terminates at Melksham in the public timetable, but then carries on to Bradford Junction to reverse ... restarts in public service from Melksham to Swindon at 07:20.   Don't think they would do that if they could just go the other way out of Melksham ...
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SandTEngineer
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« Reply #6 on: November 29, 2018, 05:45:14 pm »

Its nothing to do with the axle counters but to do with the way the signal interlocking operates.
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SandTEngineer
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« Reply #7 on: November 29, 2018, 06:18:33 pm »

Think you mean the 'Penryn Solution'.... Roll Eyes https://en.m.wikipedia.org/wiki/Penryn_railway_station

Fiendishly clever, these S&T Engineers...
I feel a drawing coming on..... Grin
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« Reply #8 on: November 29, 2018, 07:15:54 pm »

Think you mean the 'Penryn Solution'.... Roll Eyes https://en.m.wikipedia.org/wiki/Penryn_railway_station

Fiendishly clever, these S&T Engineers...
I feel a drawing coming on..... Grin

When I thought of it, I imagined a two track, both bidirectional lines with a set of points between the Swindon end of Melksham to allow terminators to go back the other way.
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rower40
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« Reply #9 on: November 29, 2018, 07:57:41 pm »

Think you mean the 'Penryn Solution'.... Roll Eyes https://en.m.wikipedia.org/wiki/Penryn_railway_station

Fiendishly clever, these S&T Engineers...
I feel a drawing coming on..... Grin

When I thought of it, I imagined a two track, both bidirectional lines with a set of points between the Swindon end of Melksham to allow terminators to go back the other way.
Ah, the Ware solution.
Where?
Yes, there.
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grahame
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« Reply #10 on: November 30, 2018, 07:14:19 am »

When I thought of it, I imagined a two track, both bidirectional lines with a set of points between the Swindon end of Melksham to allow terminators to go back the other way.

If both tracks are bi-directional, would you need the crossover?

Turnback at Melksham of trains on the Swindon - Chippenham - Melksham - Trowbridge - Westbury line would be rare in any scenario.  Chippenham and Trowbridge are both major towns (to put it mildly) - much bigger than Melksham - and with major travel requirements between them.  So an ability rather than a big spend for frequent use all day seems about right.

"Left field" are requests for the junction between Bradford-on-Avon to Trowbridge to be re-instated as a triangle ( "Bradford North Curve". If re-instated it would give a diversion route for London to Bristol via Chippenham and Bath services if Box tunnel was not available.  It would also allow MetroWest trains from Bristol to carry on after Bath Spa to Bradford-on-Avon and Melksham. 

Also at the back of minds - and highly unlikely now that so much money has been spent on an underground feeder to Thingley (even though electrification will stop 4 km short of Chippenham for some years) is feeding the overhead at Melksham SubStation - meaning that electric trains could run London to Melksham - and (let's face it) Melksham is a much bigger destination for trains from Paddington than Bedwyn.  Made all the more unlikely by so many trains moving to bi-mode technology.
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« Reply #11 on: November 30, 2018, 12:18:52 pm »

When I thought of it, I imagined a two track, both bidirectional lines with a set of points between the Swindon end of Melksham to allow terminators to go back the other way.

If both tracks are bi-directional, would you need the crossover?

Turnback at Melksham of trains on the Swindon - Chippenham - Melksham - Trowbridge - Westbury line would be rare in any scenario.  Chippenham and Trowbridge are both major towns (to put it mildly) - much bigger than Melksham - and with major travel requirements between them.  So an ability rather than a big spend for frequent use all day seems about right.

"Left field" are requests for the junction between Bradford-on-Avon to Trowbridge to be re-instated as a triangle ( "Bradford North Curve". If re-instated it would give a diversion route for London to Bristol via Chippenham and Bath services if Box tunnel was not available.  It would also allow MetroWest trains from Bristol to carry on after Bath Spa to Bradford-on-Avon and Melksham. 

Also at the back of minds - and highly unlikely now that so much money has been spent on an underground feeder to Thingley (even though electrification will stop 4 km short of Chippenham for some years) is feeding the overhead at Melksham SubStation - meaning that electric trains could run London to Melksham - and (let's face it) Melksham is a much bigger destination for trains from Paddington than Bedwyn.  Made all the more unlikely by so many trains moving to bi-mode technology.

Perhaps we will leave out the points then, I assume the new platform would be constructed out of concrete sections like the extension on Stonehouse Station.
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brooklea
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« Reply #12 on: November 30, 2018, 03:36:30 pm »

While you are re-doing the signalling, please don't limit it like it is at present - please allow trains to be reversed at Melksham in the future.
Trains can reverse at Melksham now.

??   Not sure they can being in the middle of the single line section between the axle counters.  On 2nd / 3rd Jan, the 06:10 from Swindon terminates at Melksham in the public timetable, but then carries on to Bradford Junction to reverse ... restarts in public service from Melksham to Swindon at 07:20.   Don't think they would do that if they could just go the other way out of Melksham ...
Well, I canít profess to know what can be pre-planned and loaded into the train planning system, but I know, from experience, that it can be done.
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SandTEngineer
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« Reply #13 on: November 30, 2018, 03:56:55 pm »

While you are re-doing the signalling, please don't limit it like it is at present - please allow trains to be reversed at Melksham in the future.
Trains can reverse at Melksham now.

??   Not sure they can being in the middle of the single line section between the axle counters.  On 2nd / 3rd Jan, the 06:10 from Swindon terminates at Melksham in the public timetable, but then carries on to Bradford Junction to reverse ... restarts in public service from Melksham to Swindon at 07:20.   Don't think they would do that if they could just go the other way out of Melksham ...
Well, I canít profess to know what can be pre-planned and loaded into the train planning system, but I know, from experience, that it can be done.
Yes, but it won't be signalled movement (but that might change when Thingley Junction is recontrolled from TVSC in April 2019).
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brooklea
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« Reply #14 on: November 30, 2018, 05:51:21 pm »

Yes, but it won't be signalled movement (but that might change when Thingley Junction is recontrolled from TVSC in April 2019).
Thingley Junctionís been controlled by TVSC Swindon for some time now, or are they taking control of the single line from Westbury PSB next April?
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