What is the purpose of a fixed distant?

Annetts key · 7 Mar 2021

ComUtoR said:
Apologies if Im confused but a fixed distant will always allow a train to pass it. Therefore if a train is occupying the section then how would it be protected ? If that section was a terminal platform with a buffer stop. It doesn't matter if its permissive or not. A train aproaching the distant will have a clear aspect.

1) [fixed distant] (train) [buffers] doesn't appear to have any protection arrangements.

2) [fixed distant] [stop] (train) [buffers] makes more sense.

Shouldn't a fixed distant always be preceeded by another signal rather than a set of buffers ?

Distant signals don’t have red aspects / danger (stop) arms. The section and therefore the train are protected by a signal in rear of the fixed distant signal/sign that can show red/danger. So therefore no train can approach the fixed distant signal while there is a train ahead (beyond) it.

So:

[controlled signal with red/danger] — unknown distance — [fixed distant signal] — (service braking distance) [buffer stop].

RailUK Forums

ComUtoR · 7 Mar 2021

Thanks.

Gloster · 7 Mar 2021

The basic principle of signalling is that if you have more than one train they must be separated by Stop signals, which tell the second train to stop before it runs into the first. You can have two trains on the same section of track in certain circumstances when making shunting moves, attachments, etc., but the main signals remain at stop and the use of subsidiary ones makes it clear that you are carrying out a slow speed move.

A set of buffers with a light on it is the same, in effect, as a stop signal. A fixed Distant leading onto a buffer stop stop light indicates to the driver to slow down and be prepared to stop at the buffer stop, but you cannot have a second trains following unless there is a Stop signal to separate that train from the first. This is the situation on many dead end branches. A Stop signal allows the train to enter on the single line. It then runs along, possibly for many miles, before meeting a fixed Distant signal, which tells the driver to slow down and be prepared to stop (*) at the buffer stops, which are, according to the rules, the same as a Stop signal.

A Distant signal does not protect anything, it merely gives an indication of the status of the approaching Stop signal, level-crossing gates, etc. or just a warning that a signal is imminent.

* - it says be prepared to stop at the next signal, because a normal Stop signal might be cleared when the train reaches it. Obviously, at the buffer stops the train must stop as there is no more track, but it is best not to have too many slightly different rules.

snowball · 7 Mar 2021

Until the Moorgate disaster in 1975 I think it was allowed that, whilst there would be a fixed red at a buffer stop, the preceding signal might be allowed to clear to green. After Moorgate this was changed to make the red at a buffer stop more like other reds, so that (say in a four-aspect area) the preceding signal could not clear to anything more than single yellow, and the one before that to double yellow.

Tomnick · 7 Mar 2021

ComUtoR said:
If you had a fixed distant onto the buffers. How would you control movements if the platform was occupied ?

Other folk have given some excellent answers already, but just to put it in context - we’re really talking about relatively long dead-end single lines, under ‘one train working’ regs (or equivalent with an intermediate instrument), so the section signal taking you onto the single line protects the whole lot, fixed distant and terminus platform and all, and there’s (usually) nothing to control trains returning from the terminus either. If you need to work the terminus permissively, then you’d need much more complex arrangements anyway.

ComUtoR · 7 Mar 2021

I found (document attached) so it all made sense (eventually) Just seeing references to distants into platforms kinda freaked me out

Thanks again, all.

HSTEd · 7 Mar 2021

ComUtoR said:
Apologies if Im confused but a fixed distant will always allow a train to pass it. Therefore if a train is occupying the section then how would it be protected ? If that section was a terminal platform with a buffer stop. It doesn't matter if its permissive or not. A train aproaching the distant will have a clear aspect.

1) [fixed distant] (train) [buffers] doesn't appear to have any protection arrangements.

2) [fixed distant] [stop] (train) [buffers] makes more sense.

Shouldn't a fixed distant always be preceeded by another signal rather than a set of buffers ?

Not all platforms have permissive working, so there should not be a train present if there is also a train approaching the fixed distant.

43066 · 7 Mar 2021

Annetts key said:
Distant signals don’t have red aspects / danger (stop) arms. The section and therefore the train are protected by a signal in rear of the fixed distant signal/sign that can show red/danger. So therefore no train can approach the fixed distant signal while there is a train ahead (beyond) it.

So:

[controlled signal with red/danger] — unknown distance — [fixed distant signal] — (service braking distance) [buffer stop].

In other words, distant signals don’t separate signal sections, stop signals do.

55018ballymoss · 7 Mar 2021

Tomnick said:
Hellifield’s very unusual

That one part of the quote made me smile, and is so true.
A quirky Absolute Block location with many aspects that are specific to there. I loved working there.

matchmaker · 7 Mar 2021

Gloster said:
Unless it is considered that the line will never be used in darkness or very poor visibility, the signal must have some sort of light. In this case it would be a single yellow at all times.

Many years ago I was a volunteer on the Severn Valley Railway. One summer Saturday we had an evening special from Bridgnorth to Bewdley and return. The return was going to be in the hours of darkness, so it was necessary to light all the signals. Paraffin lamps back then (1970s). I volunteered to take on the task, so spend the afternoon trimming, filling and lighting the lamps.

Being ultra keen back then I even walked the mile or so to put a lamp in the fixed distant.

This caused great consternation to the footplate crew on the return trip, as nobody could ever recall the lamp in the distant being lit!

edwin_m · 7 Mar 2021

ComUtoR said:
Apologies if Im confused but a fixed distant will always allow a train to pass it. Therefore if a train is occupying the section then how would it be protected ? If that section was a terminal platform with a buffer stop. It doesn't matter if its permissive or not. A train aproaching the distant will have a clear aspect.

1) [fixed distant] (train) [buffers] doesn't appear to have any protection arrangements.

2) [fixed distant] [stop] (train) [buffers] makes more sense.

Shouldn't a fixed distant always be preceeded by another signal rather than a set of buffers ?

The fixed distant is always preceeded by another signal in the order seen by a train approaching the buffers.

Combining your (1) and (2), the arrangement is actually as follows:

[distant] [stop signal] [fixed distant] [buffers]

The signalling ensures that only one train can between [stop signal] and [buffers]. Therefore any train getting a proceed aspect at [stop signal] can be confident there are no other trains in the way. [Fixed distant] is only a warning to the driver to brake before the buffers.

Merle Haggard · 7 Mar 2021

Going back to the days of widespread semaphore signals, it puzzled me that, on the W.R., fixed distants (of the GWR pattern) were very common bot on other regions extremely rare - I don't remember ever seeing one on the LMR.
This may have been because the GWR interpreted regulations differently from the other companies. Signalling in semaphore days was to provide route, not speed indications, and a signal which drivers knew could only display a caution aspect (because of its self evident design) seems illogical.

*An exception was the 'Mirfield Speed Signalling System' with unusual semaphore aspects.

ChiefPlanner · 7 Mar 2021

In old school rulebook - Section N - working to the point of obstruction..

Say a 313 sits down at St Albans Abbey - full protection applied , and an appointed pilotman or "competent" person guides the assisting train onto the failure - having come to a full and clear understanding with the controlling signalbox at the last working signal - in the case of this branch , the signal would be at Garston (Herts) - a mere 4 miles or so away.

Methods of working , including failures on the single line would be tabulated in the instructions pertinent to the route.

MarkyT · 7 Mar 2021

I'd say the majority of distant signals in preservation are of the fixed type. This is largely because most heritage lines are exclusively single line with passing loops, so most trains have to stop at the passing place signal box to exchange tokens or train staffs. Where a passing loop box can switch out to create a long section, sometimes distant signals can be cleared in both directions however. Distants were some of the first signals to be replaced by electric colour lights on a large scale as they were usually the furthest from the box so the most difficult manual pulls and involved the most maintenance, as well as the longest walks for lamp trimming and refilling.

ABB125 · 7 Mar 2021

MarkyT said:
I'd say the majority of distant signals in preservation are of the fixed type. This is largely because most heritage lines are exclusively single line with passing loops, so most trains have to stop at the passing place signal box to exchange tokens or train staffs. Where a passing loop box can switch out to create a long section, sometimes distant signals can be cleared in both directions however. Distants were some of the first signals to be replaced by electric colour lights on a large scale as they were usually the furthest from the box so the most difficult manual pulls and involved the most maintenance, as well as the longest walks for lamp trimming and refilling.

I believe that, on the GWSR, the only "working" distant signal is the one approaching Gotherington on the way to Cheltenham. All the others are fixed. I think this is because the line can be run with two trains in operation with Gotherington signal box locked out, hence the clearing of the signals through the section.

Efini92 · 8 Mar 2021

BanburyBlue said:
Hi all.

Can someone enlighten me as to what the purpose of a fixed distant? A fixed distant implies to me that the following home signal is always set at stop as the train is approaching. The only reason I can see for this is possibly when approaching a terminus.

So I’m guessing I must be missing something?

Apologies if a noddy question.

You’re right, that’s the basic principal of fixed distants. It can be approaching a terminus, sometimes they are used to stop a train at the start of a token section.
Worcester Shrub hill has them but they are for a reason only the Western region know.

moggie · 8 Mar 2021

Also worth noting that a Fixed Distant signal (board) on the approach to a terminal platform at the end of a branch (or indeed any other location that has one), which as others have observed could be many miles / travelling time from the preceding signal would also have the benefit of AWS (permanent magnet only of course). Just to remind the driver where they are in proximity to the buffer stop.

Efini92 said:
You’re right, that’s the basic principal of fixed distants. It can be approaching a terminus, sometimes they are used to stop a train at the start of a token section.
Worcester Shrub hill has them but they are for a reason only the Western region know.

And also worth stating the obvious that a Fixed Distant requires no signal box lever in mechanical control areas.

Dstock7080 · 8 Mar 2021

snowball said:
After Moorgate this was changed to make the red at a buffer stop more like other reds, so that (say in a four-aspect area) the preceding signal could not clear to anything more than single yellow, and the one before that to double yellow.

On LU it’s still possible to receive a green home signal and the red buffer stop is the next colour light; there are of course protection trainstops to prevent overspeed on manual Lines.

Tomnick · 8 Mar 2021

ChiefPlanner said:
In old school rulebook - Section N - working to the point of obstruction..

Say a 313 sits down at St Albans Abbey - full protection applied , and an appointed pilotman or "competent" person guides the assisting train onto the failure - having come to a full and clear understanding with the controlling signalbox at the last working signal - in the case of this branch , the signal would be at Garston (Herts) - a mere 4 miles or so away.

Methods of working , including failures on the single line would be tabulated in the instructions pertinent to the route.

Section N related to Single Line Working (on a normally double track railway), didn't it?

I have to say that I'd never considered the possibility of treating a failed train as an obstruction in that context for the purposes of assistance. There's provision in the regs for allowing an assisting train into an occupied section for that purpose, and - without checking the exact wording - it might get a bit tricky on technicalities if you take the obstruction (and its protection) away with you whilst working to point of obstruction is still formally in effect - I'm fairly sure that it certainly used to be permitted to work to the point of obstruction from both ends of a single line section simultaneously!

rower40 · 8 Mar 2021

Witham to Braintree branch; in the down direction, the signals and other relevant items are as follows:
L765 2/3rds of the way along Witham Platform 4.
L767 (red/green) protecting Cut Throat Lane (foot and cycle crossing with MSLs)
White Notley Station
Cressing Station
Braintree Freeport Station
Fixed Yellow L895
Braintree station (and bufferstops)

L895 can only show yellow. But L767 reverts to red if the lamp in L895 goes out.

Up direction:
Braintree station
L896 (red/green)
Braintree Freeport station
Cressing
White Notley
L818R - fixed yellow
L818 (red/yellow)
Cut Throat Lane LC
Witham platform 4.

L818 is approach-controlled because of the presence of the level crossing, and the speed restriction into Witham platform 4. So L818R can't ever show anything other than yellow. Again, it has to be lit in order to get a green in L896.

So this has both kinds of fixed-distants; L895 tells the driver that he's braking-distance from the buffers at Braintree; L818R tells him that he's braking-distance from L818, which can only clear from red once the train gets quite a bit closer. L818 can't show a green because of the speed restriction into the platform, and the fact that all trains are expected to stop at Witham. (One less bulb to maintain, and no need for an AWS electromagnet!)

Sunset route · 9 Mar 2021

Annetts key said:
Distant signals don’t have red aspects / danger (stop) arms. The section and therefore the train are protected by a signal in rear of the fixed distant signal/sign that can show red/danger. So therefore no train can approach the fixed distant signal while there is a train ahead (beyond) it.

So:

[controlled signal with red/danger] — unknown distance — [fixed distant signal] — (service braking distance) [buffer stop].

As with everything on the railway there are exceptions to every rule and we have distant signals (on the Brighton Main Line) that display a red aspect in normal conditions but when required as a distant the red aspect is suppressed (as is full bidirectional signalling is brought into use). Does become a pain if while using the Bi-Di you now have to extract the train that went in on the correct direction and now has to come back from the direction it came from and against the flow as the conditions in the interlocking will no longer be met to suppress the red aspect in the distant and getting two in the same pot is not looked upon very favourably.

Annetts key · 9 Mar 2021

That sounds worse than the SIMBIDS (simple bidirectional signalling system) that BR introduced in some places in the late 1980s. But that’s going off topic...

Highlandspring · 9 Mar 2021

Tomnick said:
I'm fairly sure that it certainly used to be permitted to work to the point of obstruction from both ends of a single line section simultaneously!

It still is permitted.

ComUtoR · 9 Mar 2021

@Sunset route On your signal diagram does that triangle mean anything specific ? I have a couple of odd ones like that on one of my maps but there is no map key and I couldn't find it in any reference document online. I know its for a distant on a signal plate.

Cheers in advance

Sunset route · 9 Mar 2021

ComUtoR said:
@Sunset route On your signal diagram does that triangle mean anything specific ? I have a couple of odd ones like that on one of my maps but there is no map key and I couldn't find it in any reference document online. I know its for a distant on a signal plate.

Cheers in advance

The triangle denotes a colour light distant signal as apposed to the old method of using the associated stop signal number with “R” single yellow distant or “RR” double yellow distant.

Stuart-h · 11 Mar 2021

Theres a fixed distant on the line between olive mount tunnel and the line to the mersery rail at Bootle.

Greybeard33 · 11 Mar 2021

Manchester Metrolink is to get a fixed distant for an unusual reason.

The original Metrolink lines to Bury and Altrincham had block signalling on the segregated alignments, with two-aspect (red-green) colour lights. There were no yellow distant signals anywhere on the network.

Over the years the block signalled areas have been gradually converted to Line of Sight operation, so now only Brooklands to Altrincham is block signalled. Brooklands to Timperley is controlled by Metrolink-owned interlocking, while the Network Rail Deansgate Junction box controls the section from Timperley to Altrincham over NR metals.

The final stage of conversion is to extend LoS through Timperley right up to the NR boundary, leaving just the NR section block signalled. But the NR interlocking, which will remain unchanged, has a lamp proving interface with the first northbound Metrolink signal, sited just before Timperley. If that signal were removed, the preceding NR signal would be permanently at Danger.

The solution is to convert the Metrolink signal from red/green to a fixed yellow, so the lamp proving will still work. From the driver's point of view the yellow signal will just be a reminder that they are entering the LoS area (it will be followed by a tramway-style white bar signal protecting the exit from the Timperley turnback siding).

This fixed distant will be the first and only yellow signal on the Metrolink network!

Tester · 11 Mar 2021

Greybeard33 said:
Manchester Metrolink is to get a fixed distant for an unusual reason.

The original Metrolink lines to Bury and Altrincham had block signalling on the segregated alignments, with two-aspect (red-green) colour lights. There were no yellow distant signals anywhere on the network.

Over the years the block signalled areas have been gradually converted to Line of Sight operation, so now only Brooklands to Altrincham is block signalled. Brooklands to Timperley is controlled by Metrolink-owned interlocking, while the Network Rail Deansgate Junction box controls the section from Timperley to Altrincham over NR metals.

The final stage of conversion is to extend LoS through Timperley right up to the NR boundary, leaving just the NR section block signalled. But the NR interlocking, which will remain unchanged, has a lamp proving interface with the first northbound Metrolink signal, sited just before Timperley. If that signal were removed, the preceding NR signal would be permanently at Danger.

The solution is to convert the Metrolink signal from red/green to a fixed yellow, so the lamp proving will still work. From the driver's point of view the yellow signal will just be a reminder that they are entering the LoS area (it will be followed by a tramway-style white bar signal protecting the exit from the Timperley turnback siding).

This fixed distant will be the first and only yellow signal on the Metrolink network!

That really does sound like the tail wagging the dog - lamp proving a signal which serves no function is a little silly!

30907 · 12 Mar 2021

Tester said:
That really does sound like the tail wagging the dog - lamp proving a signal which serves no function is a little silly!

But cheaper than altering a NR interlocking.

Greybeard33 · 12 Mar 2021

30907 said:
But cheaper than altering a NR interlocking.

Especially when said Solid State Interlocking (SSI) is over 30 years old and NR has a captive customer!

On the TfGM side, I suspect it may be more a question of time than money. NR had planned to resignal the Deansgate Junction area from the Manchester ROC, but that project seems to have receded into the indefinite future. Maybe NR said that no S&T resource was available to modify the old SSI. Whereas TfGM wants to be rid of its own obsolete SSI and wrap up its contract with Thales for the replacement Tram Management System.

What is the purpose of a fixed distant?

Established Member

RailUK Forums

Established Member

Established Member

Established Member

Established Member

Established Member

Attachments

Veteran Member

Established Member

Member

Established Member

Veteran Member

Established Member

Established Member

Established Member

Established Member

Established Member

Member

Established Member

Established Member

Member

Member

Attachments

Established Member

Established Member

Established Member

Attachments

Member

Member

Established Member

Member

Veteran Member

Established Member