Rule 39a And Why It Is Necessary

Not true, GWR ATC has been in existence since 1906. They are the pioneers of auto train control in the UK.
ATC stayed in use into the 1980's on ex-GWR territory.

https://mysite.du.edu/~etuttle/rail/atcgwr.htm

 

Was this change especially relevant to the concept of the thread? You seem to be dancing around the central thrust of the topic by focusing on details while not addressing the core fact that two-aspect signalling in TSW is currently fundamentally broken.

 

Fair enough, thanks for your reply MRFS, hopefully it ascends towards the top of the pile in the not too distant.

 

Which is why I brought up this topic with respect to Peak Forest, back when it was more likely to get a post-release patch.

Players who rely on the HUD and do not actually read the signals are especially affected by this deficit, because what the HUD shows them is the state and position of the Outer Home signal, not the Distant. They receive no instruction to expect the Advance Starter (or any intermediate signal) to be at Danger, and thus to ensure that their braking distance matches their sighting distance (which for them is the distance between Home signals).

Meanwhile, players who do read the signals and research how those signals work will see the Distant at Caution and react to it, but then also see the Outer Home standing at Clear and assume, per 39a or whatever era's equivalent, that all subsequent signals to the next Distant signal are also at Clear. So nobody is happy.

This is compounded by the HUD failing to properly reflect the state of a Distant arm on the same post as a Home arm.

There is technically a similar problem with German signals, but it is much less acute because German signalling always gives a reasonable braking distance between stop signals. Their combined Hp/Vr signals also show the same problem as semaphore Home/Distant combinations.

DTG have insisted that TSW is technically capable of resolving these problems, yet these problems persist across multiple route releases and are not patched post-release. It really undermines confidence in TSW's attitude towards quality control.

 

Thanks MRFS. I was aware that it wasn’t actually called Rule 39A by the 80s, but I’m always conscious that most players of the game are casual players rather than subject matter experts, and the more we get into the rule numbers etc the more people switch off! My understanding was that, whether applied manually by the Signaller or automatically by a track circuit, the experience from the Driver’s perspective was similar, and that is what I’m hoping to see re-created in TSW, as a Driver sim.

Great to hear that it’s in the pile of things to look at, and if it can rise to the top one day soon that would be greatly appreciated by us all!

 

Thanks IKB, useful added detail. I’m not sure which part of my post you’re saying was not true, though?

 

Unfortunately as a bloody layman I don´t use the correct terms. By "double signals" I refer to Pic1. It´s quite confusing because the right outer signal gives me a green, but how´s this related to my track, being my track the second from right? And how does the driver manage changing signal sides? I mean obviously he can´t rely on the fireman. (Pics 2 & 3)
Pic1


Pic2

Pic3

 

Take another look at the gantry. Do you notice the height difference between the left and right signals? That’s your indication that these are not independent signals, but diverging signals for the same track (sorry if the terminology isn’t right, I’m no expert on UK signalling). Both apply to your track on the left. The tall signal applies if you continue moving along your track, the lower (left) signal if you’re divering to the left.

In other words, if they’re all red, you stop. If the tall one’s green, you continue at track speed (distant signal permitting). If the lower one’s green, you continue at diverging speed in the indicated direction (in this case left).

 

Yes, I understood this from eldomtom2´ explanation. Just to illustrate how confusing it is for a layman like me. Now, for signal side switching and darkness? The green signal in Pic2 is considerably higher positioned. Does this have to do with visibility from the driver side?

 

See, the thing is I don't see "we can't capture every little detail and nuance" as a good reason for not including the basic principle. I would also like to know more details on the 1972 regulations rather than just saying "there were classes of trains where C4.6/C5.9 did not apply".

 

The Driver’s route knowledge would tell him exactly where the signal he needs to spot is located, including which side of the line it was on (usually it’s the left, but by no means always). Approaching the location, if the signal was better sighted from the right-hand side of the loco, the Driver would cross the cab and view it from the other side, or ask his fireman to do so. A good fireman would also be aware of the signals on the route best viewed from the right hand side, and make a point of looking out for them and calling out what they show.

There are a number of reasons why a signal might be on a very tall post like the one shown. It might be, for example, that there’s a bridge or other obstruction in front of it, so by raising it above the height of the bridge it can be seen much earlier. However, one possible reason is, as you say, to enable the Driver to see a right-hand side signal from the left-hand side of the cab, over the boiler.

 

Interesting explanation. Thanks again for sharing!

I didn´t mean to hijack the thread. It was, though, somehow related.

 

In this case, the extra height of both signals (note the left-hand one would be visible from the Driver's side of a train on the Slow line) will be to make the semaphore arm appear against a bright sky background, where it's easier to read from a distance and at speed. Indirectly, it does also make it easier to see from the Driver's side of the cab, because the boiler gets in the way less if the signal is quite far ahead when sighted. Spare a thought for the lampman who had to go up both posts every dusk and dawn!

In the following picture, the signal is bracketed over to the left of the track (there being insufficient room for a post there) so that it is visible from nearby. This would be important for a section signal that the train would often be expected to wait at, rather than a Distant.

Most signal arrangements can be figured out with a bit of thought, with some especially complex layouts needing a bit of specific knowledge in advance. Once worked out, you memorise the pattern. The most vital part is understanding which signal arms apply to the track you're presently on; you can then distinguish between "stop" versus "proceed".

Usually not all tracks have an associated signal, as about half of them will be reserved for trains travelling in the opposite direction. From Wavertree to Ditton, you have a typical case of four tracks "paired by use", ie. a pair of fast lines for each direction, then beside them a pair of slow lines for each direction. Conversely, from Weaver Jn to near Crewe, you have an equally typical case of four tracks "paired by direction", with the Slow lines flanking the Fast lines. These are just two patterns which you can keep in mind when interpreting signals. The line through Lime Street Cutting to Edge Hill was changed from "paired by direction" (as simulated) to "paired by use" (today), simplifying the junction operations at Edge Hill.

 

I'm rather confused by this. Either Rule 39A is possible in the editor or it isn't. I don't see how the various details and exemptions are relevant to that.

You are seemingly arguing that that the nuances of the rule's application are such that including it in a simplified "always applies" form would be worse than not including it at all.

 

What, they aren't hoisted from the ground like on German semaphores?

 

I have absolutely no idea what you're saying. If you're saying I'm misinterpreting what you're saying, why don't you point out what you think my error is?

 

This is a bit passive agressive, which I do not expect from a staff member...

 

(Removed by me. The second post conveys everything this tried to. Could delete but people below reference it.)

 

I don’t fully follow what you’re saying here, but the OP is basically correct. I think you may be misunderstanding it slightly, but I can’t exactly understand your meaning so I’m struggling to assist - my apologies.

If it’s an area you’re interested in then I do recommend reading through the whole thread, as it’s a good read (it starts getting a bit fraught at the end, but hopefully it will recover).

 

This:

The way I understand this would be a valid case with the advance showing a warning.
I did read the thread now and it sounds like it wasn't a universal rule. In any event, what TSC discussions taught me, if I see an advance warning I have to be ready for any home being at danger.

Applying 39a means that when trains meet at a station, they both have to crawl in and trip their respective entry signals since their starter is at danger. I mentioned Falmouth because it's a perfect layout to assess the rule (single track main with double track stations, advance on the main, entry and exit at each station, in each direction).

For no-HUD players this could only be a problem if they drive assuming 39a where there isn't 39a.
Without 39a, passing a warning and seeing a clear doesn't mean I can sprint.
With it, it does.
Hence, assuming the absence of 39a is safer from a driver's perspective.

This is very programmable using advanced signaling logic.
The exit / starter signal is two-aspect.
The entry / home signal is internally three (or four) aspect, however outputs two aspects. Danger and warning translates to danger, clear and shunting to clear. Shunting activated when at warning and the player is close and slow.
The advance signal is two-aspect, reacting the the entry / home (only).

 

It was and is a universal rule with exceptions.

Well yes, if it's a single track line...

It's also safer to crawl along at 10mph, but obviously real drivers don't do that.

And I can't follow your first post at all.

 

In the specific case of a single line, the incoming driver would not have authority to proceed beyond the section signal anyway, because he doesn't have the token for that section. Holding the Home signal as a warning is thus redundant, since the driver will be expecting to stop regardless.

The Distant signal would only come off if there is a "long section" token in use (which guarantees to the driver that the section beyond the station is clear), or if the signalman has the token ready to exchange with the driver on the fly. The timetable might be set up to make the latter case typical for one of the passing trains. On many single lines, the Distants were rarely worked and were eventually fixed at Caution to reduce maintenance.

However, from a gameplay perspective I wouldn't mind seeing 39a applied even in this case. It makes things more consistent for the player, even if it's not strictly prototypical.

 

Every time I see this thread I can't help but think of Rule 34.

And kids, if you don't know what Rule 34 is, don't Google it...

 

I would expect it being due the trains in indian being so overcrowded and due to animals and people being able to free roam on the railroads kind of

 

In Western Australia two people burned to death in a massive fireball train accident as the driver took a shunt signal and kept his speed with no braking. Well at least until the last minute.

The train either didn't slow down to a crawl or it sped up when it saw the shunt signal. The other train was moving slowly into the loop and still had diesel tankers hanging out the back end when the National Rail train struck.

For some reason this was not standard practise and trains would always be held at the home signal (starters here on single line are called departures but now I think as rules have been modified/changed etc may have a different name).

https://en.wikipedia.org/wiki/Hines_Hill_train_collision





The shunt signal was a signal authorizing a slow speed train movement for shunt purposes only. Not to be used for mainline trains which in this case it was. I sense things were being 'expedited'......

 

Yes I think the terminology got confused somewhere. Even some cursory research proved difficult. But Australia is the same essentially as England/Britain as we had semaphores and the British system too.

The Home signal is the entrance to a station, not a block.

The Starting signal is the departure from the station into the block section ahead. Absolute block won't permit another train in there except a permissive signal which is a low speed signal for shunt movements. So the driver will go slow enough to stop before hitting another train.

I'll see if I can find an example in the game.

 

Maybe time PZB came to the UK.

 

While in a sense this is true the use of the term "station" could be confusing. The home signal controls the entrance to the section of track controlled by a specific signalbox.

 

For clarity, "station limits" here means the section of track controlled by one signalbox.

 

So a signal box may have jurisdiction over 4 or 5 block sections?

Or can you use Ambergate Chinley Peak Forrest route as an example?

These days with centralised train control in the UK and Australia, they will control hundreds of kilometres or track.

Even on the West Coast Main line in the UK wouldn't it be classed as a proper station where a platform exists (and signals) and then marshalling yards? So CTC can be in charge now of 20-30 'signalboxes' or stations.

 

"Station limits" is a term used with absolute block signalling, and absolute block signalling is not used on the modern-day WCML.

 

You may find this diagram useful. This is cropped from SimSig documentation, as they depict Absolute Block working as an overlay on a fundamentally NX-style panel. Beware that panel diagrams are very much NOT TO SCALE.



Usually the location of the signalbox itself would be marked on the diagram. In this case it is not, but we can assume it would be in the vicinity of Pen-y-fford station and the crossover. Thus you can see that Home signals are "in rear of" the box and Starter signals are "in advance of" the box.

The solid grey segments of track show where the presence and positions of trains can be inferred from track circuits. The open segments show where track circuits are not fitted, and trains must be deconflicted by sight or reminder devices (if within station limits) or by the block telegraph (if in the block sections). The block telegraph is represented here by the coloured dots on the track.

Obviously, since the distances are much greater, trains will usually spend most of their time in those block sections and hidden from track circuits, which is why the block regulations are so precise about how to operate the block telegraph.

 

Which is why absolute block signalling is nowadays only used where the entire line is not fitted with track circuits. Where a line is entirely fitted with track circuits absolute block can be discontinued and the line controlled from a single signalling centre. Fundamentally absolute block signalling is about controlling trains when their precise location cannot be known at all times.