Distant Signals And The Hud

I'm not talking about approach control, or berth locking/limiting of aspects.

If you want specific evidence, look at the IRSE papers.

 

A UK semaphore distant.

I rather thought that was the heart of this discussion: if block and aspect controls were germane to this discussion I would have mentioned them.

I wonder if some players - not necessarily thinking of anyone who has contributed to this discussion thus far - are conceptually regarding a single semaphore yellow [1] as being equivalent to a single MAS yellow - they're not; and are not equivalent in a number of ways.

[1] assuming two-position semaphore, capable of showing either yellow or green.

 

Wow. This discussion.

Just, wow.

So much misinformation and misunderstanding I don't even know where to begin.

TL;DR i will find out from the engineering team about adding ability to see distants in amongst the upcoming signals and see what that might look like. I make no promises about when/if, only that i'll find out and if it's achievable in a workable timescale, i'll see where I can fit it.

Ok...

The signalling implementation in TSW is not a fudge as some have suggested. It's fairly accurate to how real world signalling works and real world signalling engineers have been involved since its inception. Consequently, it's an order of magnitude more involved to set it up than the one in TS Classic, but the end result is much much more understandable.

The signals are linked to the track, each signal has routing tables that define permitted routes from that signal to any other signals down the line as appropriate (some "technically" workable routes are not actually permitted for various reasons, so this is a subset of the full list, with those routes marked "disabled"). Each route has a fairly extensive set of parameters such as the maximum approach speed, the speed that must be followed upon entering the route, what class of route it is (shunt, call on, mainline, yard etc) - I forget all the parameters, there's quite a few.

Distant's are mapped according to various parameters, such as being pointed to a group of other signals or checking for speed drops upcoming, or particular paths being taken for example.

So what happens with this is that you're driving along the line and you need to get from there to the bay platform up ahead, the dispatcher will look at the signal routing tables and figure out that your next signal is AB01, the signal after that is SB04 and then you can get routed into the bay platform. However, the bay is occupied by a train. There is a second route from SB04 to the bay however that only requires the outer half of it, and that route now works. Ok, so we have AB01 via Route 2, to SB04, via Route 5, which is a Call On route, into the bay platform. The dispatcher will attempt to set the junctions and lock the routes, also checking for occupation of any of the track and if all is good, the signal blueprints are then told to go update their visuals. The signal blueprints will check what routes are set and understanding onward occupation will be able to then set the appropriate aspects.

Within each "route" there are many track sections. As you proceed along the "route", and the back of your train clears a track section, it's occupation and allocation is released. So you see this progressively releasing behind the train, section by section. This is a facility on the real railways that allows trains BEHIND you to not need you to finish your entire route, if you've cleared everything that's needed and you're taking a different path. Let's say you're proceeding along and you're going straight over a crossing, but another train wants to take the other path over the crossing to go, essentially, from your right to your left. As soon as you're safely clear of that crossing, you can set the system up to release the sections and allow the signal holding the other train to allocate its route over the crossing, there's no conflicts and the railway runs a little more efficiently.

There's no limitation or heritage particularly caused by the way signalling systems have been developed. The systems used in todays routes on TSW are barely the same as the ones in the early routes. We have redeveloped the UK Signalling systems a couple of times, and there are multiple variations of US systems. German has seen enhancements since Ruhr (Rapid Transit was not a strong start, I'll freely admit) but has been fundamentally more stable than the others.

Someone suggested earlier there's incompatibility between semaphore and colour light signalling - not true. Since the whole thing fundamentally uses the core basics of track sections, block allocations, routes and such, and then the signals layer their own logic on top of that (which is largely visual only in many cases), it's much easier to have compatible systems in TSW than it was in TSC.

Where you're seeing a problem on NTP I suspect is a simple bad implementation of a signal - if you're closely following another train as you go towards Leeds, heading into Standedge Tunnel, you'll get a GREEN signal as you pass the signal box, followed almost immediately by a RED signal at the entry to the tunnel. Essentially as I understand it, the signal in front of the tunnel shouldn't be there - that didn't exist in the time of the NTP route, was added later on and was a misread from the vast amount of documentation the team have to sift through. "remove it then" is not quite as simple as it sounds however I'm afraid; though I believe there's been discussion in the team about resolving this one I will go and find out where it got to. Again, i'm not promising a fix, just that i'll see what the scope for one is there and what other problems it could cause.

If you're seeing problems with the interface between CLS and Sem signals let me know That's the only issue i'm aware of and as I explained, it's just that there's an extra signal where it shouldn't be.

Matt.

 

I think what MRFS is getting at is, a yellow semphore distance signal in the ON position, is only, ever, advising the driver to reduce their speed. It provides no other information, at all. You can *assume*, you can figure out based on route knowledge that its "likely" indicating things, but very simply, if a distant is on, it's advising you to reduce your speed. Hence, it is considered a speed signal.

The modern flashing indicators are basically combining speed info with route info, rather than considering the UK as exclusively route-based, think of it as primarily route-based, with a sprinkling of speed-hints added around various places that have been added on over time.

Matt.

 

In the case of a single yellow MAS signal that yellow applies to the next signal only. A single yellow on a UK semaphore distant does not apply to just the next signal - it can apply to one, two, three, four, five or six consecutive signals in advance. I think five is the practical maximum, but older LBSC and NER layouts may have had six - so it's not the same thing.

Distants that are maintained "on" for a divergence are a speed signal - and it was by no means universal that there was a separate post for advance warning of that divergence. As I have said before, and it bears repeating - a UK semaphore distant signal does not convey any information about the occupancy of the line ahead, it conveys information about the speed that a driver is expected to be allowed to run at, and as previously said that is not a specified speed saving that it would be at less than the maximum speed listed in the Sectional Appedix.

I haven't had the time or the inclination yet to dig them out of my archive. When I get chance, I will, but I'm not expecting to have chance for quite a while as I'm out of the country towards the end of the week.

 

There seems to be some significant revision of history going on here.

The runaway at Armagh happened on the 12th of June 1889; the Regulation of Railways Act 1889 was given Assent on the 30th August 1889. By your use of the "Lock Block and Brake Regulations" it suggests that you're using a digital source that needs further proofing.

Have you ever read any Railway Inspectorate reports - or aware of the role of the Inspectorate? Once a mode of working has been recommended and agreed and a Formal Undertaking signed, nothing can change that undertaking unless there is an accident requiring a reinspection - and otherwise the RI/Board of Trade were effectively powerless, until the 1889 Act gave them teeth. [1]

The change from time interval to space interval was already in motion from the late 1860s, with the Board of Trade and then the Railway Inspectorate becoming progressively more reticent to approve new passenger lines with time interval working. The Newry and Armagh Railway opened in stages between 1864/1865 so in 1889 was operating on the Formal Undertakings of 13/14 years prior: they were Time Interval, obviously. From memory the last double track passenger main line to be approved with Time Interval working was c.1868.

Time Interval working continued well beyond 1889 for goods lines, where it was refined into the Permissive Block system and there were several companies that continued working goods lines by telegraph bells only - in fact I'm pretty sure (without returning to the Sectional Appendix) that the goods line through the yard at Rowsley was still bells only in the period modelled.

No, not at all. There may have been the odd company that specified speeds, but not one that I've come across: all rulebooks I've seen from the 1840s - 1890s with time interval specified in the Rule Book (also subject to Board of Trade approval) a time interval of a specific number of minutes - hence the name of the operating style.

No, utterly wrong here (sorry). Yes, the "block signal" or "station signal" was capable of displaying "Caution" but there were also auxiliaries or distant signals that gave warning at a distance of what the block/station signal was displaying - some of these Distants had quite exotic shapes and the more go-ahead railways had a glossary of engravings in the back of their rule books as an aide memoire to their drivers where there was a joint station or running powers.

You are conflating the "Caution" aspect displayed by block/station signals with the "Caution" aspect displayed by distant signals. The two are somewhat different.

I hope you'll forgive me for saying this, but if what you've written is your understanding of the history: you are way, way, way off-beam; in a whole mix of areas - not only in the evolution of signal aspects, but getting the date of the most important Act in the period wrong. Are you very quickly reading online sources and then producing a post, rather than writing from innate knowledge?

[1] the 1889 Act was unusual insofar as it finally gave the Inspectorate the legal teeth to demand retrospectively the installation of continuous brakes, interlocking and the block system.

 

At the risk of sounding petulant; but it is a risk I'm quite happy to take: ask yourself who is the signalling historian and the signalling engineer in this discussion? Are you a published author in this area? Utterly genuine questions.

What do you know of standard signalling principles? Or the training given in Absolute Block teaching courses? If you did, then I don't think you'd either phrase your questions in the manner that you have or make such arbitrary statements with no revealed knowledge of signalling history or signalling evolution. I may be wrong, and I apologise if I have a mistaken impression.

I'm afraid your dogmatism is misplaced here. It's a speed signal. It has no other function.

I'm not sure that I need to explain approach control - that area of aspect limiting is a completely different area of technology and has no bearing whatsoever on a UK semaphore distant. As I said upthread: if block or aspect controls were germane to this discussion: I would have mentioned them - you yourself have said approach control is not considered speed signalling: so why are you getting hung up on it?

For what it's worth, the inclusion of a distant via a GCR or GPR in the block circuit for HNC purposes isn't approach control, obviously.

 

Bingo! The penny has finally dropped - although it isn't exclusively for a diverging route - it is for any route from that distant until the next distant.

No, not exclusively so - a speed signal is one that imparts speed information to the driver. Granted, there are many different varieties of signal - some which can be tied into specific target speeds - and to the same extent a UK semaphore distant can be tied into a specifc speed: less than the booked speed in the Sectional Appendix. Clearly, there are so many different speed limits that this could apply to, the use of a particular signal for a dedicated speed band is well-nigh impossible (and at night prior to the 1920s, indistinguishable from a stop aspect, relying entirely on route knowledge).

A UK semaphore distant at clear means that there is no need for caution - that's why at night the aspects are the same as a stop signal; conversely, a distant that is on indicates to the driver to pay attention to their speed. It is worth commenting that the reason for the change of aspects for distants from red/green to yellow/green is part and parcel of the creation of the third and fourth aspects for UK signalling; as well as making the distants easier to spot - particularly "on" distants - Bound, especially, had a "thing" about isolated distants and decreed that they should be painted with black and white horizontal stripes - much like Belisha Beacons.

The evolution of the French system from that of a mechanical speed system to a multiple aspect system, and the treating of the various differing styles of speed signals (some of which can be regarded as standalone distants, or inner and outer distants) is fascinating: especially after the Code Verlant in 1934. Perhaps something for another thread, though - as I'd not like to conceptualise a HUD for a French mechanical system. Likewise with Spain (and here the situation is more complex, as standardised practices came in long after the formation of RENFE in 1941 - no Railway Clearing House in Spain!) where there are lines with three position homes and three position distants and to a certain extent that survives in fragment with the concatenation of yellows and greens - trying to fit those styles of signalling into a HUD would require a lot of thought - as there is much more nuance between "stop" "slow down" and "go".

 

For clarity - what do you mean by "colour light signals" - do you just mean "colour light signals" or "Multiple Aspect Signals" or mechanical colour light signals?

Flashing yellows - yes, of course they are speed signals. A flashing yellow with a PLJI is both a speed and route signal.

Think carefully of the deixis and particularly the anaphora of "signal" above. It is quite clearly referring directly to the UK two position semaphore and its use in the UK. Reread the sentence again, but this time think of a UK semaphore remaining the same visually, but referring to specified speeds - hopefully then you'll understand fully what I wrote in the manner that I wrote it. Especially as the following sentence makes reference to the red/green aspects prior to the introduction of yellow.

 

To be fair, that's absolutely no skin off my nose whatsoever - happy days all round, I feel.

However - how would you, yourself describe flashing yellows - would they be a subset of route signals, or junction signals (as indeed they can be subsumed within the sphere of junction signalling)? I'm quite happy to describe a flashing yellow as a speed signal because it is naturally different from a steady yellow - granted that this is only within the aegis of UK MAS signalling. Let's not forget that the reason there are flashing aspects is to enable the driver to negotiate the junction safely, which usually requires a reduction in speed - again in UK tradition, that speed isn't defined at the signal.

However, it may be salient to note that the IRSE textbooks talk in terms of "speed reduction"; logically leading to the conclusion that, at heart, a flashing yellow without a PLJI is a speed signal within a route signalling system therefore [Strong Route, Weak Speed] as mentioned upthread.

 

As promised upthread, I have gone digging through my archive (albeit only part-way), with respect to Distant Signals: so herewith a transcript of LMS document ERO 50239: “Instructions as to the Sighting of Signals”. This was printed in 1936; but containing the Ministry of Transport guidance from 1928 and of itself an amplification of the 1925 notice that mandated the use of yellow glass in addition to red and green.

These are the relevant sections for Distant signals:

• Up and Down Distant Signals for each block post, to be provided on all running lines which have two position stop signals. One Distant Signal in each direction, with the necessary control from each Signal Box, is sufficient for a number of block posts closely grouped together, unless there are good reasons to the contrary.

• At diverging junctions only one Distant Signal should be provided, worked for the junction line over which the highest speed is permissible, unless in exceptional circumstances more are essential. Where special circumstances, e.g. permanent speed restrictions, justify the adoption of an un-worked signal, it should be secured in the warning position and not coupled up or duplicated for directing purposes.

• The interval between a Distant Signal and the first Stop Signal to which it applies must be such that a train in proximity to the former, and moving at the highest speed can be stopped before passing the latter.

• All signals, as a rule to be immediately on the left of, or vertically over, the line to which they apply.

• Semaphore Distant Signals to be distinguished from Stop Signals during daylight hours by yellow coloured arms, with notches cut out of the ends. They must be placed below, and be controlled by Stop Signals, if they are carried on the same post and applicable to the same direction. A Distant Signal placed under a Stop Signal of a box in the rear must, unless the circumstances are exceptional, be repeated under all Stop Signals in advance of that signal which are worked from that box, with the necessary additional control by such signals.

• Front lights of all running signals to be red for Danger, yellow for Caution (including the warning position of Distant Signals), and green for clear, with white used for backlights to be only visible when the signal is at Danger.