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Author Topic: Single line capacity - is an hourly passenger train each way possible?  (Read 235 times)
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« on: February 20, 2021, 09:13:30 am »

From National Rail - as at this morning

Start date 20/02/2021  00:00
End date 21/02/2021

Route affected

Great Western Railway between London Paddington and Bristol Temple Meads / Exeter St Davids / Penzance.
 Also between Portsmouth Harbour and Cardiff Central
 South Western Railway between Salisbury and Bristol Temple Meads

Great Western Railway:

Buses will replace trains between Bath Spa and Bristol Temple Meads.

Some trains will be diverted between Swindon and Bristol Temple Meads and will not call at Chippenham or Bath Spa.
Until late evening, a hourly train shuttle service will run between Swindon and Bath Spa calling at Chippenham.

Trains between Portsmouth Harbour and Cardiff Central will run between Portsmouth Harbour and Swindon calling additionally at Melksham.

Customers should use rail connections between Swindon and Cardiff Central South Western Railway.

South Western Railway
It is not yet known how South Western Railway are affected by this engineering work.

Where it says "calling additionally at Melksham", actually only some of them are calling at Melksham - those which are closest to the normal train times.  Fair enough at the current time.   What this does do is show that the line can handle an hourly passenger train each way, though I grant you that lack of much freight and thinned out services on the double track main lines at both ends of the single line section makes it easier today than it would be on a typical full service weekday.

Coffee Shop Admin, Vice Chair of Melksham Rail User Group, and on the board of TravelWatch SouthWest.
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« Reply #1 on: February 21, 2021, 08:34:02 am »

So ... how did they do?  "Pretty Well".

How it was run

Hourly train from Westbury at about xx:12 into Swindon at xx:54, and from Swindon at xx:24 arriving at Westbury at xx+1:02. Times varied by a few minutes (but only a few minutes) in any hour; 38 minute running time achieved in the example quoted includes stops at Chippenham, Melksham and Trowbridge. Without other trains getting in the way (key comment!) the service daily could be run clockface, hourly, using 2 x 90 m.p.h. Turbos, hourly, to these timings, on current infrastructure.

Time for passengers, Freight Paths, etc

4 minutes slower in my example Westbury to Swindon; 1 minute perhaps accounted for needed by slow approach to Platform 2 at Swindon. The two trains pass each other at or very close to Chippenham station, and an extra 5 minutes in the "cycle" from there to Swindon and back, and from there to Westbury and back (leaving turn arounds of 21 minutes and 5 minutes) would work. That five minutes allows for pathing, and for extended passenger operations at stations that will happen from time to time. The closeness of the two trains at Thingley - short gap as the up train comes off the single line before the down train takes it - leaves a path open for a freight or other working each hour. You can see this used at Melksham with none-passenger services passing at 12:08, 13:14, 16:00 and 16:14 (managed to get 2 in that hour!!)


Service robustness of passenger trains generally good yesterday. The 17:28 call (at Melksham, northbound) was 13 minutes late, due to a delay (don't know why) to the train south of Salisbury, and that meant that the pass at 17:47 of the southbound train was 8 minutes late as it had to wait at Thingley. At first glance, it looked like an early running freight got in the way of the 17:28 as it swept through Melksham at that time, but in practise good signalling control took advantage of the gap and sent it through ahead of time.

Infrastucture improvement

We talk / look / see the need for the ability for trains to pass each other between Melksham and Thingley Junction and indeed for robustness in a fully running timetable this makes huge sense; for passengers trains, redistributing the short turn around at Westbury and the longer turn around at Swindon to be more even, and allowing a pair of freight services to similarly pass in the hour with a degree of robustness in there too.  In my view, the loop would need to be fast running and long ("dynamic") to avoid slowing / stopping trains in one or both directions to the substantial loss of positive effect from the loop by prolonging journey times.I also note the run (round trip time) of several minutes from Thigley Junction to Thingley East junction, where the single line traffic on "the Melksham Line" is sharing the main down London to Bristol via Bath line.  Prior to the singling of the Melksham line, a double junction at Thingley meant this pinch point did not exist; I understand that restoration of that, or a crossover at the junction, is complex/impractical/impossible due to the cant on the main line tracks to allow fast running.

Calling additional (new) stations?

Timings seen yesterday would appear to allow passenger calls in both directions at Royal Wootton Bassett. More difficult (and it's where the dynamic loop becomes needed) to call at Staverton and/or Ashton Park as in the Systra / SWLEP report of 2019 (mirror ((here))).

P.S.  and bit off the immediate topic. Passengers for South Wales yesterday from Trowbridge and south thereof were encouraged to change at Swindon.  Must have been frustrating (though not many long distance passengers in lockdown) with a 40 minute wait at Swindon towards Wales, and the trains at almost exactly the same time in the other direction - so a 0 or 60 minute wait.  I noted one or two where people probably made it, one or two where the train from Swansea was a few minutes late and the Portsmouth train left before it arrived, and one or two which might have repeated my memory of a couple of years ago of doors on the IET only opening after doors on the Westbury train had been closed!
« Last Edit: February 21, 2021, 08:43:24 am by grahame » Logged

Coffee Shop Admin, Vice Chair of Melksham Rail User Group, and on the board of TravelWatch SouthWest.
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