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Length of up through line at Swindon?

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Length of up through line at Swindon? 26/12/2019 at 00:57 #122527
JWNoctis
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So...yes, I've just screwed up. Had a lapse in my scan cycle, and did not notice that a Class-6 goods, the 550m-long 6A12 in default TT had fouled both points into P3 while standing at signal 65, before the ARS had set a route to 59 for the following HST. Lessons learnt.

But the question is, how much clearance do we have in rear of signal 65 without fouling at least the points to P1/2/3? Given how often goods trains were timetabled to stand there for following Class-1's to pass, it might make an useful note in the platform and loop lengths section of the manual.

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Length of up through line at Swindon? 26/12/2019 at 01:21 #122529
Underwood
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At a rough guess around the 250-300m mark? That's to the points which are by the station, otherwise a 550m freight shouldn't really affect the access, as usually a London HST would use the Rushey Platt relief, and then straight into 1 or 3. I believe the crossover speed is faster than the ones near the station.
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Length of up through line at Swindon? 26/12/2019 at 08:46 #122534
JWNoctis
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Underwood in post 122529 said:
At a rough guess around the 250-300m mark? That's to the points which are by the station, otherwise a 550m freight shouldn't really affect the access, as usually a London HST would use the Rushey Platt relief, and then straight into 1 or 3. I believe the crossover speed is faster than the ones near the station.
Makes sense. Looks like the route from up main to up relief at Rushey Platt is uncontrolled, while the routes over the two crossovers closer to the station to P3 had flashing yellows. But I guess either shouldn't make all that much difference, as the trains are already supposed to be slowing for arrival, be it straight-in from RL, or over one of the crossovers from ML?

Yet it's still somewhat strange that not more trains were timetabled to run over the relief line. Was it discretionary, depending on factors such as non-stop traffic three blocks behind, or a stationary class-4/6/7/8 of unusual length fouling the neck points? But yes, it's me who had messed up here.

Last edited: 26/12/2019 at 09:27 by JWNoctis
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Length of up through line at Swindon? 26/12/2019 at 10:45 #122537
Jan
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While this information is more easily available to the respective developer or people with a tester's license, there's a little trick with which anybody can find out the length of a track section, at least as long it is visible on the panel.

Open the Incident Control Panel, head over to the Track Sections tab and use the "click to select" button to get the identity of the track circuit in question, e.g. TSUE for 42's overlap.
Now replace the initial "T" with an "U" (i.e. TSUE -> USUE) and head over to the TSRs tab. Click on the "Add..." button, switch to "Individual subroute" mode and look up the U... subroute you've determined previously.

When you select a subroute, you can then see that the From/to position and speed limit fields are populated with some default values that represent the respective subroute's actual length and speeds.
For track sections containing some pointwork, determining which subroute with its respective suffix (-AB, -BA, AC, etc.) matches which physical direction can be a bit tricky, although
a) line speeds might provide a clue, and
b) track section ends are supposed to be numbered clockwise from A to Z, starting at the 12 o'clock position

I your case, USUE-BC and USUE-CB are the relevant subroutes, which are shown with a length of 180 m, which is therefore the additional length you have available over and above the standage available between 42 and 65. (If the rear of your train would be overhanging TSUD as well, then 2403A points will remain locked normal and you're in the same situation as in your original post).

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Last edited: 26/12/2019 at 13:53 by Jan
Reason: typo

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Length of up through line at Swindon? 26/12/2019 at 12:58 #122539
JWNoctis
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Jan in post 122537 said:
While this information is more easily available to the respective developer or people with a tester's license, there's a little trick with which anybody can find out the length of a track section, at least as long it is visible on the panel.

Open the Incident Control Panel, head over to the Track Sections tab and use the "click to select" button to get the identity of the track circuit in question, e.g. TSUE for 65's overlap.
Now replace the initial "T" with an "U" (i.e. TSUE -> USUE) and head over to the TSRs tab. Click on the "Add..." button, switch to "Individual subroute" mode and look up the U... subroute you've determined previously.

When you select a subroute, you can then see that the From/to position and speed limit fields are populated with some default values that represent the respective subroute's actual length and speeds.
For track sections containing some pointwork, determining which subroute with its respective suffix (-AB, -BA, AC, etc.) matches which physical direction can be a bit tricky, although
a) line speeds might provide a clue, and
b) track section ends are supposed to be numbered clockwise from A to Z, starting at the 12 o'clock position

I your case, USUE-BC and USUE-CB are the relevant subroutes, which are shown with a length of 180 m, which is therefore the additional length you have available over and above the standage available between 42 and 65. (If the rear of your train would be overhanging TSUD as well, then 2403A points will remain locked normal and you're in the same situation as in your original post).
I understand these are also track circuit lengths? Never knew you could do that!

And here's what I've got(4.3 build 7):
USUG = 280m between signals 42 and 65
USUE-CB = 180m of up main over points 2415A (P3)
USUD-CA = 60m of up main over trailing points 2404B
USUC-CB = 60m of up main over points 2403A (P1,2,3)

So if I got it right, that makes it a maximum of 280m before fouling points 2415A, and 460m before locking points 2403A normal, for a train standing at signal 65.

A 550m train like the one I've had would have stood with its tail lamp right over points 2403A altogether.

Incidentially points 2415A had 25mph and 2403A had 20mph speed limit, while points 2120 at Rushey Platt had 75mph. Looks like there would have been a difference after all.

Thank you!

Last edited: 26/12/2019 at 13:02 by JWNoctis
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Length of up through line at Swindon? 26/12/2019 at 13:58 #122542
Jan
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JWNoctis in post 122539 said:
while points 2120 at Rushey Platt had 75mph. Looks like there would have been a difference after all.

Note that there's a small sim error in this area though, which means that the 85 mph on the Up Main (= 10 mph speed differential towards the Up Relief at 75 mph, hence the free green at signal 53) is currently missing in the sim and is shown as 125 mph, too.

Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick.
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Length of up through line at Swindon? 26/12/2019 at 14:33 #122544
JWNoctis
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Jan in post 122542 said:

Note that there's a small sim error in this area though, which means that the 85 mph on the Up Main (= 10 mph speed differential towards the Up Relief at 75 mph, hence the free green at signal 53) is currently missing in the sim and is shown as 125 mph, too.
Was wondering about that a bit - 50mph of difference did sound a bit much without any kind of approach control.

Thanks for the clarification!

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Length of up through line at Swindon? 26/12/2019 at 16:36 #122545
Steamer
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JWNoctis in post 122539 said:


I understand these are also track circuit lengths? Never knew you could do that!
Yes, they are. Keep in mind though that signals may not necessarily be right on the boundary of two TCs, and that trains usually stop short of red signals (not sure what the SimSig default is).

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Length of up through line at Swindon? 26/12/2019 at 18:10 #122547
GeoffM
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When the Rushey Platt turnout to the Up Relief became a high speed junction, pretty much everything scheduled to stop was routed up that Relief - not the main. I don't recall when that was though. It's possible the timetable you used predated it, or was incomplete with line codes.
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Length of up through line at Swindon? 26/12/2019 at 20:04 #122554
Albert
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As far as I know I've always used the Main while playing SimSig. I was honestly surprised when my GWR train took the Rushey Platt line when coming from Bath in October.

The train had to wait until its platform was free because of some disruption, so I thought that I had been looped.

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Length of up through line at Swindon? 26/12/2019 at 20:26 #122555
JamesN
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GeoffM in post 122547 said:
When the Rushey Platt turnout to the Up Relief became a high speed junction, pretty much everything scheduled to stop was routed up that Relief - not the main. I don't recall when that was though. It's possible the timetable you used predated it, or was incomplete with line codes.
Away from my reference material at present, but if I recall - the conversion was done August Bank Holiday Weekend in 2006.

It never was timetabled separately, and signallers were free to use either option as they saw befitted the situation - although as eluded to upthread it was most certainly the faster route via the Up Relief.

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Length of up through line at Swindon? 26/12/2019 at 20:44 #122557
GeoffM
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JamesN in post 122555 said:
It never was timetabled separately, and signallers were free to use either option as they saw befitted the situation - although as eluded to upthread it was most certainly the faster route via the Up Relief.
I hadn't noticed that. Even the current TT does not have a line code at Wootton Bassett, or a timing point with a line code at Rushey Platt.

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Length of up through line at Swindon? 26/12/2019 at 21:55 #122561
lazzer
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Albert in post 122554 said:
As far as I know I've always used the Main while playing SimSig. I was honestly surprised when my GWR train took the Rushey Platt line when coming from Bath in October.

The train had to wait until its platform was free because of some disruption, so I thought that I had been looped.
I've been driving trains along the Box road for 12 years now, and on only a couple of occasions have I been routed into Swindon on the Up via the main line. On one of those occasions I was running reversible on the Down Main from Wootton Bassett Junction.

All the other hundreds of times have been via the Up Relief at Rushey Platt. It's certainly "normal" to go that way.

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Length of up through line at Swindon? 26/12/2019 at 23:11 #122566
clive
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Jan in post 122537 said:

b) track section ends are supposed to be numbered clockwise from A to Z, starting at the 12 o'clock position
That's sort of correct, but 12 o'clock isn't always where you think it is. In particular, you can't say that the mid-point of the drawing is 12 o'clock, because that could change the labelling depending on a minor change in drawing.

Also, for technical reasons we only go up to O (so 15 ends).

For this purpose each track circuit has a "shape". Shapes in turn have a "spine" which is normally horizontal throughout and has all points normal along it, though that isn't always the case. The rule then used in SimSig is to walk clockwise from the left end of the spine to the right end, noting each track end that you pass in order as pointing left ("L"or right ("R"); include the two ends of the spine in this. Put a dash between each pair of letters that aren't the same; there will have to be an odd number of dashes. End A is always just after the middle dash. Once you've found end A, walk clockwise around the track circuit, never crossing a track within it, and label the ends in the order you find them.

Since I have Euston open in front of me, I'll point at track circuit 72, which runs between Backing Out Roads 1-3 and signals 71 and 73. It has 6 ends, three at the left, two along the top, and one at right. The "spine" runs from BOR 2 to 71/73. Walking around gives you the sequence of letters LLRLR (the first two Ls are from BORs 2 and 3, the RL from the scissors, and the final R from the right hand end; BOR 1 isn't involved in this). We add dashes to get LL-R-L-R. So end A is the one heading through the scissors towards BOR 4 and the Down Carriage Shed. B heads rightwards, C, D, and E go to BORs 1 to 3 in that order, and end F heads through the scissors towards signal 68.

On the other hand, remembering the clockwise rule and looking at what subroutes are available can be enough to work out which end is which.

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Length of up through line at Swindon? 27/12/2019 at 09:47 #122575
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I'd just taken the clockwise rule from the "Basic Guide to Sim Construction" overview on the Wiki, which must have been simplifying things a little. Thanks for the in-depth explanation.
Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick.
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Length of up through line at Swindon? 27/12/2019 at 18:42 #122595
GeoffM
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There are also areas where the track is "upside down", so you start at 6 o'clock instead (perhaps the sim got flipped upside down, or real world scheme plans were used which were oriented differently). Track shapes with traps/run-offs which don't form any part of a signalled route or overlap also get skipped in the lettering sequence and then get lettered after the "active" ends have been labelled. Finally, each sim has its own shape library which may predate a standard library we have now - though there are always sims with new track shapes which aren't in the library.

It's just a template anyway. If two developers label something slightly differently (eg one skipping trap ends and the other not) then it doesn't matter.

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Length of up through line at Swindon? 30/12/2019 at 15:15 #122642
clive
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Jan in post 122575 said:
I'd just taken the clockwise rule from the "Basic Guide to Sim Construction" overview on the Wiki, which must have been simplifying things a little. Thanks for the in-depth explanation.
You're welcome. The "clockwise rule" is right, but it's not always easy to get right in complex situations. The important thing is that "12 o'clock" is not necessarily at the middle of either the symbol on the screen or the track circuit on the ground.

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