Four track for Filton Bank - ongoing discussion

[whole diary]

[JontyMort]

Metalrail can take a bow - as it was a desire to see his photos that made me sign up.

To be clear, I presume the latest ones are at the northern end - i.e. north of where the old two-track alignment was slewed over to the east side - so the old tracks here are the mains and the new ones are the reliefs?

I take it that "Up" in this context is to Paddington via Badminton. That had me foxed at first, as I was expecting it to be "Down" from Paddington via the rhubarb curve. Is zero here at Bristol East?

Having a look here might help: http://www.firstgreatwestern.info/coffeeshop/index.php?topic=13113.msg236581#msg236581 and here: http://www.firstgreatwestern.info/coffeeshop/index.php?topic=13113.msg248151#msg248151

Thanks for this and the other replies. I am familiar with the general layout (often doing Worcester-Bristol or Brum-Bristol) but it's different seeing the photos as opposed to from a moving train. It has been interesting seeing new track appear over the last weeks - and suddenly change sides as you go down! It looks as though the finished product will be a good job.

Does anyone know what the linespeed will be from Dr Day's to Parkway? The Voyagers should cut a minute or two off if they get a clear run.

[grahame]

Does anyone know what the linespeed will be from Dr Day's to Parkway? The Voyagers should cut a minute or two off if they get a clear run

I would suspect that there will be little change to timings until a/the major timetable change across the West that's postponed from January 2019 so - err - sometime.  And even then, an extra minute or two of padding might be left in schedules.     There's the whole "robustness v speed" thing, and with compensations for late running becoming easier to do through electronics and delay-repay, there is little to tempt the rail industry to trim a minute or two.   Speed-ups become worthwhile when they can save a train, or when they are so dramatic they bring in more custom.  Clever thing for the TOCs^▸ (Train Operating Company) is to drive slowly up the hill so that passenger don't realise there's slack in there, and by the way that will save fuel too.

[TonyK]

Welcome from me too, JontyMort! I've been following this with particular interest, and still know less than most other folks on here. It has been a huge undertaking though, and it's nice to see it coming at last to being used. As grahame says, though, don't expect too much speen increases, but less late running hopefully. Plus of course the new services to Paddington via Badminton.

[Red Squirrel]

Does anyone know what the linespeed will be from Dr Day's to Parkway? The Voyagers should cut a minute or two off if they get a clear run.

I was just discussing this with my daughter, who takes an interest in these things: I am presuming that the installation of 75mph S&C^▸ (Settle and Carlisle ) is a clue here!

[Adrian]

No.  Banner Repeaters are used where the required sighting distance of a signal cannot be achieved (e.g. due to curve or obstruction such as an overbridge).

There's an interesting banner repeater on the up line between Patchway tunnel and the station that combines with green and yellow aspects and a junction repeater (i.e. two banners, each of which uses coloured LEDs when the junction signal is yellow or green, and white LEDs when it is red.
Seems surprising that they deemed a repeater necessary in the up direction but not the down direction where the signal before the tunnels is hidden by the A38 overbridge.  Cardiff-bound trains often crawl for the first half a mile out of Patchway station even though the signal has cleared to green while the train was stopped at the station.

[JontyMort]

Does anyone know what the linespeed will be from Dr Day's to Parkway? The Voyagers should cut a minute or two off if they get a clear run.

I was just discussing this with my daughter, who takes an interest in these things: I am presuming that the installation of 75mph S&C^▸ (Settle and Carlisle ) is a clue here!

Good point, suggesting 90 on the mains. I agree that they're not going to trim the booked timings but it should make the XC^▸ (Cross Country Trains (franchise)) working a bit more robust - especially down the bank, where at present a late-running XC at Parkway can get caught behind something.

An oddity at Parkway is that they don't yet seem to be using the southernmost platform (1?) for southbound XC, even though that is the obvious non-conflicting route. Maybe that will change in December. The new layout allows parallel movements west out of Parkway to both Bristol and Cardiff... but only if the Bristol train is in the correct platform.

[Red Squirrel]

...suggesting 90 on the mains.

Anyone know what the limit was on the old layout?



Image by Andy Kirkham [CC BY 2.0  (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

[metalrail]

An oddity at Parkway is that they don't yet seem to be using the southernmost platform (1?) for southbound XC^▸ (Cross Country Trains (franchise)), even though that is the obvious non-conflicting route. Maybe that will change in December. The new layout allows parallel movements west out of Parkway to both Bristol and Cardiff... but only if the Bristol train is in the correct platform

They've been using P1 since May for the southbound 'local' GWR^▸ (Great Western Railway) stopping services to Brighton / Westbury / Weymouth etc which call between xx.19 and xx.23, as these are the ones I generally catch from BPW^» (Bristol Parkway - next trains) to LWH.  Seeing as a lot of them run late it's good that they're separated from the XC services which call around xx.30 on P2, so there isn't the old queue for a platform to come free like there used to be

This is one thing i'm looking forward to the four tracking helping to solve, as usually when my local service is delayed, the XC service will be given priority to depart which further delays the local service.  Obviously with the new layout they won't be tailing each other down the bank after FIT any more

[SandTEngineer]

The Relief Lines will be generally 60mph on the Up, increasing to 75mph between Narroway Hill Junction and Filton Abbey Wood and 75mph on the Down throughout.  The main lines will be 75mph throughout.  Speeds obviously decreasing for the curves at each end.

[SandTEngineer]

No.  Banner Repeaters are used where the required sighting distance of a signal cannot be achieved (e.g. due to curve or obstruction such as an overbridge).

There's an interesting banner repeater on the up line between Patchway tunnel and the station that combines with green and yellow aspects and a junction repeater (i.e. two banners, each of which uses coloured LEDs when the junction signal is yellow or green, and white LEDs when it is red.
Seems surprising that they deemed a repeater necessary in the up direction but not the down direction where the signal before the tunnels is hidden by the A38 overbridge.  Cardiff-bound trains often crawl for the first half a mile out of Patchway station even though the signal has cleared to green while the train was stopped at the station.

There are two types of BANNER REPEATER signal.  The first is the most common type that has a black bar on a white background.  The bar is horizontal if the signal being repeated is at danger (Red aspect) and the bar is at 45 degrees in the upper left quadrant if the signal being repeated is clear (Yellow, Double Yellow or Green aspects).

The second type has a black bar on a white background or a black bar on a green background (known as a GREEN BANNER REPEATER).  The bar is horizontal on a white background if the signal being repeated is at danger (red aspect), and the bar is at 45 degrees in the upper left quadrant on a white background if the signal being repeated is clear (Yellow, Double Yellow aspects only).  The bar is at 45 degrees in the upper left quadrant on a green background if the signal being repeated is clear (Green aspect only).

If the signal being repeated applies to a diverging junction then sometimes a 'side by side' double banner repeater is provided to indicate which route is set at the junction before the repeated signal can be seen.  This can be of either type.

The reason for the latter more recent GREEN BANNER REPEATER type is to allow for better train performance, as a driver knows when the repeated signal is clear to a Green aspect and he can therefore continue at linespeed without waiting to see the aspect actually shown by the repeated signal.

PHEW....you lot love asking technical questions

Edit to Add: A GREEN BANNER REPEATER does not always have to show the bar at 45 degrees in the upper left quadrant on a white background.  That is not necessary if the repeated signal can only show Red or Green aspects.

[metalrail]

PHEW....you lot love asking technical questions Grin

That's cos you're the man in the know! 

[SandTEngineer]

PHEW....you lot love asking technical questions Grin

That's cos you're the man in the know! 

I was always taught that its never too late to learn something new (even after 50 years in the S&T^▸ (Signalling and Telegraph) business ).

[JontyMort]

If the signal being repeated applies to a diverging junction then sometimes a 'side by side' double banner repeater is provided to indicate which route is set at the junction before the repeated signal can be seen.  This can be of either type.

There's a good example of one of these on the down line between Bournville and Kings Norton. The cross-city stoppers take the left route into the platform at KN and then the down slow (this is the start of the quadruple track section down to Barnt Green) while the right-hand route goes to the down fast (and 45 becomes 90). The through line has a green banner repeater - a sight for sore eyes when one has crawled out of New Street.

[SandTEngineer]

Here is a photograph showing the three possible states (and yes, another type of signal ID plate; this one indicating that its a GREEN BANNER REPEATER):


Image thanks to the St.Albans South Signalbox website

[SandTEngineer]

...suggesting 90 on the mains.

Anyone know what the limit was on the old layout?



Image by Andy Kirkham [CC BY 2.0  (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

I'll have a look in my historic records.  Might take a few days!