Signalling for modellers who don't know much about signalling

[Junctionmad]

 

 

the distant will be 'on' as i pass it but the diverging signal for the loop is nearly always 'off' when i sight it having bought the train down to an acceptable speed to either stop at the signal or proceed into the loop (there is no tpws overspeed fitted there iirc)

yes this was the idea of a  distant fixed permanently " on " , irrespective of the state of the nest stop signal , that practice I understand 

 

 

 

once in station limits the signaller could return the home to danger and (depending on local circumstance/layout) accept another train from the next box down the line up as far as his (now at danger) home signal even if the first train is still within station limits for some reason

historically, this could only be done if the clearing point wasn't fouled , or accepted under the " warning " arrangement . The fact that another train was within the station limits was not the deciding factor 

Edited October 27, 2017 by Junctionmad

[big jim]

yes this was the idea of a  distant fixed permanently " on " , irrespective of the state of the nest stop signal , that practice I understand 

 

 

historically, this could only be done if the clearing point wasn't fouled , or accepted under the " warning " arrangement . The fact that another train was within the station limits was not the deciding factor

 

the only 'warning' signal ive ever seen/worked under is approaching llandudno, the home has a subsiduary with 'W' and 'S' stensilled miniature arm

 

they have them at shrewsbury too, speaking to the signaller a few months back and he said he'd used the 'warning' for the first time in his 20 year career a couple of days previously as for whatever reason he couldnt get any other signal to release into an empty bay platform

[St. Simon]

I recognise that but it is the fact that having slowed the train to a crawl/almost a stop, the junction signal is (and any subsequent and visible signals may be) (cleared to) green whereas if the junction signal cleared to a (single) yellow and the next remained at red, the forgetful driver who may have wound up the controller when the junction signal cleared to green and forgetting that he was about to take the divergent route, would still have a visual reminder ahead of him.

 

Am I wrong or is there an instruction that says the driver shouldn't be able to see a green signal beyond a red to avoid a driver unconsciously ignoring the red?

 

Hi,

 

The 'forgetful' driver scenario is taken care off by enforcing the rule that a junction signal shouldn't be more than 800 metres from the first facing point in the route, he also has speed boards to remind him of the speed, by leaving the next signal 'on', drivers may not make use of the full linespeed as he is coming up to a red, which would slow him down even more.

 

There isn't an 'instruction' per say, but there is 'read-through' risk, and there can be controls added to hold the signal that you could read through to at danger until the previous signal has been passed, I know there are these controls at Kennington Junction near Oxford and near Westbury on the Berks & Hants Line. But this also based on the Sighting Committees view of the risk.

 

Simon

[The Stationmaster]

Another common one is trains approaching a speed restricted turnout into a loop or junction for which the signal has been cleared; the more correct procedure would be for the signalman to bring the train to or almost to a stand before clearing the appropriate signal similarly to the example above.  In modern signalling, this sort of situation is 'approach lit' by the proximity and speed of the train; if it is approaching too quickly over more than one sensor, the signal will not clear and the driver has to phone the signaller to ask for the road; the same principle is employed.

 

 

 

Not necessarily so.  If the train is booked to take the diverging/slower speed route the signal would normally be cleared in the normal way (which might be long before the train arrives) - this would apply at a physical junction where routes separate or at a running junction where trains cross from one running line to another.

 

However if the train is not booked to be diverted from one route (or running line) to another then the procedure you apply would be adopted (unless the Signalbox Special Instructions give an exemption from applying that procedure, example Heywood Road Junction at the east end of the Westbury Avoiding Line had such an exemption for trains diverted to the Westbury Avoiding Line).

[The Stationmaster]

Question on that last point. A private siding- which could be an extensive works system with its own signalling- would have a trap point or an arrangement of points to protect BR's running lines but, when the sidings were open to the running lines for a mainline loco to shunt wagons in and out, what rules would then affect a works loco working in the private area?  Would there ever be direct access to the works system from the mainline or would there always be an intermediate exchange siding. if so what penetration of BR (GWR, LNER etc.) by works locos would be permitted and vice versa?   

 

 

Officially the only things which are necessary are a trap point to protect the running line from errant movements out of the private siding(s) and a gate across the railway (in line with the boundary fence between the private siding and the railway.  Such gates were frequently the victims of 'shunting incidents' and seem to have frequently fallen into disrepair or decrepitude rarely being closed by the 1960s (and possibly earlier).

 

The owner of the private siding has always been legally responsible for the conduct  and management of rail operations on his property although at smaller sidings the normal 'big railway' Rules & Regulations tended to be applied plus any additional special Instructions - the latter should normally have been included in the Sectional Appendix to ensure they were brought to the attention of railway company staff likely to work in such a siding.  Bigger private siding/railway networks, or those belonging to large concerns such as the NCB would often have internal work procedures and Rules but generally I think it's fair t say these wouldn't necessarily apply where 'main line' movements were being made into/out of the private sidings.  Nowadays it is rather more formalised through ROGS but the situation is really little different - thus should I for example write Instructions for the owner of a private siding (e.g. a power station) where trains and crews off the national network will run the relevant Instructions at the boundary have to be agreed with NR and sometimes even with individual train operators.

 

The use of an exchange siding is basically a matter of operational convenience and could be either on railway land or on the private siding property with locos and staff of one concern or the other having the necessary authority to work on the other company's lines.

 

On the separate subject of  'a slow pull' it was always something I strongly discouraged if I came across a Signalman using it (which was very rare in my experience).  Drivers are expected to know the Rues just as much as Signalmen are so they will understand that if they are brought nearly to a stand at a semaphore signal before it is cleared then the line is only clear to the next stop signal in advance.  

[The Johnster]

Stationmaster makes a very good point, as he usually does being an authoritative voice on such matters.  Signals should have one meaning only to a driver, that being the one denoted by what it is shown.  Stop means stop. Clear means clear to the next signal.  Shunting, Calling On, or similar subsidiary signals mean Stop, or, when they are cleared, Proceed to the next signal as far as the line is clear under caution being aware that the section may be occupied.  Imposing extra meanings with 'slow pull-offs' or similar unofficial methods may facilitate and expedite traffic, but sooner or later someone will turn up who is not in on the game and misunderstands what is meant, with the possibility of dire consequences increased.  Clear meanings and definitions are vital in this field, and the reason that drivers were not supposed to know about 'approach released' and such signals.

 

Of course, familiarity breeds contempt as is human nature, and it is difficult to conceal the nature of an 'approach release' from drivers and others who observe the same predictable behaviour from a signal on a daily basis.  It hits the fan when it doesn't clear one day...

[Pacific231G]

Officially the only things which are necessary are a trap point to protect the running line from errant movements out of the private siding(s) and a gate across the railway (in line with the boundary fence between the private siding and the railway.  Such gates were frequently the victims of 'shunting incidents' and seem to have frequently fallen into disrepair or decrepitude rarely being closed by the 1960s (and possibly earlier).

 

The owner of the private siding has always been legally responsible for the conduct  and management of rail operations on his property although at smaller sidings the normal 'big railway' Rules & Regulations tended to be applied plus any additional special Instructions - the latter should normally have been included in the Sectional Appendix to ensure they were brought to the attention of railway company staff likely to work in such a siding.  Bigger private siding/railway networks, or those belonging to large concerns such as the NCB would often have internal work procedures and Rules but generally I think it's fair t say these wouldn't necessarily apply where 'main line' movements were being made into/out of the private sidings.  Nowadays it is rather more formalised through ROGS but the situation is really little different - thus should I for example write Instructions for the owner of a private siding (e.g. a power station) where trains and crews off the national network will run the relevant Instructions at the boundary have to be agreed with NR and sometimes even with individual train operators.

 

The use of an exchange siding is basically a matter of operational convenience and could be either on railway land or on the private siding property with locos and staff of one concern or the other having the necessary authority to work on the other company's lines.

Thanks Mike, as always you've made this very clear. Presumably, the gate fulfilled the legal requirment for the railway to be entirely fenced off as with level crossing gates, accomodation crossing gates and so on.  

[The Johnster]

Route knowledge is of great importance here, both of drivers and guards.  Signing the road requires not only familiarisation with the speed limits, loads, permitted lengths of trains, gradients, and signals, but also includes knowledge of operating procedures into and out of private and exchange sidings, which while mostly similar in principle differ widely in detail and actual 'on the ground' practice, as well as hugely in size and form.

 

If you are not modelling an actual location (in which case you can use whatever procedure is/was used in real life to whatever extent you can model it), your friend as a modeller here is an imaginary entry in the appropriate Section Appendix (this may be imaginary itself of course), authorising whatever procedure you choose to use.  But keep works locos on works land inside the gate and trap point unless you know that they were permitted on BR track; very few ever were.

Edited October 29, 2017 by The Johnster

[phil-b259]

 

 

.....(which implies the home must be visible from the box?);

 

Not necessarily. Don't forget the basic track circuit has been in use for over 100 years now and as such it does not automatically follow that the Home has be visible* from the box if they are employed to confirm train positioning. Likewise, electrical signal arm repeaters fitted to the block shelf also mean that the requirement for the signalman to physically see the actual arm to check it has responded correctly to the lever operation is not necessary.

 

Application of these electrical devices facilitated rationalisation of signal boxes and a reduction in staff manning levels well before the adoption of colour light signalling.

[Chimer]

Not necessarily. Don't forget the basic track circuit has been in use for over 100 years now and as such it does not automatically follow that the Home has be visible* from the box if they are employed to confirm train positioning. Likewise, electrical signal arm repeaters fitted to the block shelf also mean that the requirement for the signalman to physically see the actual arm to check it has responded correctly to the lever operation is not necessary.

 

Application of these electrical devices facilitated rationalisation of signal boxes and a reduction in staff manning levels well before the adoption of colour light signalling.

 

Thanks for spotting the supplementary question ...... Understood, but surely track circuits don't allow the signalman to know the approaching train has "come almost to a stand", so he can clear the home with the section signal still at danger?

 

Chris

[peanuts]

Thanks for spotting the supplementary question ...... Understood, but surely track circuits don't allow the signalman to know the approaching train has "come almost to a stand", so he can clear the home with the section signal still at danger?

 

Chris

they dont usualy you would have a buzzer connected to the approach locking this would sound when the train occupies the track circuit before the signal whilst it is at danger .the buzzer would sound for the required length of time the train  should take to be at or nearly at a stand 

[TheSignalEngineer]

Thanks for spotting the supplementary question ...... Understood, but surely track circuits don't allow the signalman to know the approaching train has "come almost to a stand", so he can clear the home with the section signal still at danger?

 

Chris

The track circuit was normally 200 yards long if the line was not fully track circuited to the box in rear, which was only done if a train could go into loop before reaching the box or similar circumstances to enable signalman to clear the Block without seeing the tail lamp, then the berth track would sometimes be 100 yards. The annunciator mentioned above would sound for 10 seconds on LMR lines.  On lines Absolute Block lines with a colour light Home signal the lever could be pulled but the signal would only clear after the train had been on the berth track for a certain time, based on typical deceleration rates and brake release times, to enable the driver to stop if the signal didn't clear or get the brake off and keep the train rolling if the signal cleared. 

[Junctionmad]

again folks, you can see how the subject can rapidly leave the topic of the thread and get bogged down in the minutiae

[Junctionmad]

Another common one is trains approaching a speed restricted turnout into a loop or junction for which the signal has been cleared; the more correct procedure would be for the signalman to bring the train to or almost to a stand before clearing the appropriate signal similarly to the example above.  In modern signalling, this sort of situation is 'approach lit' by the proximity and speed of the train; if it is approaching too quickly over more than one sensor, the signal will not clear and the driver has to phone the signaller to ask for the road; the same principle is employed.

 

This sort of thing is part of poor running practice generally on models operated by those not intimate with railway procedures, like running around a train and propelling the stock back into the platform without stopping, notwithstanding that the vacuum brakes are hard on, and the loco needs to stop for coupling, connection of vacuum (or air) hoses and the brake has to be blown off before the propelling can take place.  Don't get me started about train formations or locos without continuous brakes on passenger trains, or privately owned factory locos running around loose all over BR...

5.6 CLEARANCE OF SIGNALS AT DIVERGING

JUNCTIONS

• this instruction applies if:

- a train is to pass from one line to another at a junction

where speed is to be reduced, AND

- the route to be taken by the train is NOT that shown in

the Working Timetable (or Notice amending it), AND

- the junction stop signal is NOT approach released

• you must not clear the junction signal until the approaching

train is close enough to it to ensure its speed is sufficiently

reduced

 

Note that three things must be present for your  comments to be true

[Junctionmad]

the only 'warning' signal ive ever seen/worked under is approaching llandudno, the home has a subsiduary with 'W' and 'S' stensilled miniature arm

 

they have them at shrewsbury too, speaking to the signaller a few months back and he said he'd used the 'warning' for the first time in his 20 year career a couple of days previously as for whatever reason he couldnt get any other signal to release into an empty bay platform

I wasn't referring to a "warning signal ", but the warning arrangement ie old rule 5.  whereby a train can be accepted even if the clearing point is fouled etc .  I don't know much about todays new fangled stuff !

[RailWest]

I wasn't referring to a "warning signal ", but the warning arrangement ie old rule 5.  whereby a train can be accepted even if the clearing point is fouled etc .  I don't know much about todays new fangled stuff !

I don't think that 'warning' signals are 'new fangled'  - they certainly existed in the 1930s :-)

[big jim]

I wasn't referring to a "warning signal ", but the warning arrangement ie old rule 5.  whereby a train can be accepted even if the clearing point is fouled etc .  I don't know much about todays new fangled stuff !

As rail west says, not exactly new fangled!!

 

HOWEVER......

 

There is a new version of it called a POSA signal (proceed on sight authority signal), I think I've got my head round how it works but I've never actually seen one, I'm sure simon can enlighten us about it futher but it looks exactly like a position light shunt signal mounted below a main aspect but it has the ability to flash 2 white lights, from what I can make out it is used in high density areas where the train in front may be say sat in the next station but foul of the overlap for the signal behind it, a way of keeping trains moving as it were, as a driver you would be expected to travel at a speed to be safe to stop short of any obstructions etc, same principal as a shunt signal

 

As I say I've not seen one but have had a brief on them

[Colin_McLeod]

Interesting two threads in one. First are numerous attempts to provide a simplified guide to signalling as per the thread title. There is also a very detailed discussion of signalling systems on the prototype. The interaction between these "two threads" is an amusing combination of frustration with the "experts" and pointing out the errors and exceptions to those who are attempting to keep things simple.

[TheSignalEngineer]

again folks, you can see how the subject can rapidly leave the topic of the thread and get bogged down in the minutiae

But those are the things that make it look right or wrong. Everyone seems eager to discuss the colour or shape of the seats in a coach, but blithly accepts a layout in a magazine with a Conflat running with a single A type container loaded at one end, a superb model of a WD with sound at five chuffs to the bar or another with the BR crest facing the wrong way. An exhibition layout with signals worked in an unprototypical manner or trains going into a Goods Loop at the same speed as a through runner on the Main detract from the experience for me.

[TheSignalEngineer]

Interesting two threads in one. First are numerous attempts to provide a simplified guide to signalling as per the thread title. There is also a very detailed discussion of signalling systems on the prototype. The interaction between these "two threads" is an amusing combination of frustration with the "experts" and pointing out the errors and exceptions to those who are attempting to keep things simple.

Deciding where signals are needed is a very straightforward matter. It largely depends on two factors, where the points, level crossings, etc are located and what moves the train operators want to make. Mounting the signals only requires that they do not foul the structure gauge requirements and that they can be seen in adequate time without the risk of confusion. So far all stuff learned when in short trousers, figuratively speaking. 

Next come the complicated bits. How do you give the driver a clear understanding of several different circumstances when the signal can only show On or Off? If I am making this move can I make that one at the same time? To switch these points, which other points have to be in a particular position first and which cannot be moved afterwards? 

[Junctionmad]

Deciding where signals are needed is a very straightforward matter.

The thing about common sense, it's isn't not at all commonplace nor most of what's done is actually sensible

 

Many layouts are appalling signalled with clearly the view that these things are " ornaments" . Hence the point of this thread.

 

If we then get around to the minutiae , well that's a bonus

Edited November 2, 2017 by Junctionmad

[Clive Mortimore]

The thing about common sense, it's isn't not st all commonplace more most of what's done is sensible

 

Many layouts are appalling signalled with clearly the view that these things are " ornaments" . Hence the point of this thread.

 

If we then get around to the minutiae , well that's a bonus

Hi Junctionmad

 

To stop me making an appalling mess with my ornaments would you be kind enough to have a look at my planned layout Sheffield Exchange Mk2 . I would like to install the signalling as I wire up the track and control panel not as an after thought. The thread has drifted a wee bit about various multi aspect colour light signals, all very interesting but I fear not 100% applicable to a model terminus station with a short visible approach. 

[LNER4479]

Well, in for a penny, in for a pound, as they say...

 

As this fascinating thread was (I think?) related to signals on model railways, I thought I'd post this sequence of photos from my Grantham layout. There are a total of 13 working signals so far (with more to add), interlocked with the points and the control system so thought it might be of interest if I outlined how each one is positioned, what it 'means' and how it operates. Happy for the experts to point out the shortcomings (seriously!) but hopefully not too many 'howlers'.

 

The prominent signal in the foreground is controlled by Yard Box and applies to both the down main (to its right) and the down relief (to its left). I'll say straightaway that Grantham is by no means the best 'typical' example of a traditional steam age signalling system, but let's see how we go. This signal, despite appearances, is not junction signal; it is sited 'in advance of' (I think?!) before the series of trailing connections immediately ahead of it and thus provides protection for mainline trains from those points. This pointwork allows a variety of shunting moves to take place at the south end of the station. If any of these points are changed (reversed) to be set for a shunting move then the interlocking system doesn't allow the signals to be pulled 'off'.

 

A northbound express is due. Having checked with the next box that the route ahead is clear, the signalman at Yard Box (the actual signalbox can be seen behind the Gresley A1) clears the down main signal. Note that, at this stage the distant signal below it doesn't clear, as the signal in the distance is still 'on' (at danger). Due to the close proximity of the signalboxes at either end of the station, the length of the block section is quite short hence the distant for the next signal box is mounted on this signal. He doesn't have separate 'home' and 'starter' signals; this is his only 'stop' signal which must, therefore. make it the section signal (experts please confirm!)

 

At the north end of the station lies North Box and, having checked the line ahead is clear to the next box (in reality Barrowby Road, but not included on the model), the signalman at North box pulls 'off' his corresponding signal. In this case it is an older somersault type so it lowers but means the same thing. This now causes the distant signal to clear so that the driver knows that the route right through the station is clear. In reality, North would have separate levers for these (red for his stop signal and yellow for this distant, which he controls); on the model, the control system logic automatically pulls of the distant, via a snazzy little 5 second delay timer unit my clever electronix mate knocked up for me.

 

As the train passes, Yard Box returns his signal to danger. The slotting arrangement automatically causes the distant to also return to danger. North's signal remains cleared however, as the train has yet to pass that. Once it does, North can return his signal to danger and we're back to photo 1.

 

In reality, the signal featured was more complex at Grantham itself as it had additional miniature signals (which I think were 'calling on' arms in this case) but, as others have already pointed out, modelling almost always involves compromise so I haven't included them.

 

Hope that is of some interest to some. I can happily do more of these although I might need to do some fresh photography as this is the only signal for which I have a sequence of photos like this. I hasten to add that these pictures were taken some years ago; the scenery is somewhat more developed these days!

Edited November 2, 2017 by LNER4479

[Compound2632]

At the north end of the station lies North Box and, having checked the line ahead is clear to the next box (in reality Barrowby Road, but not included on the model), he pulls 'off' his corresponding signal. In this case it is an older somersault type so it lowers but means the same thing. This now causes the distant signal to clear so that the driver knows that the route right through the station is clear.

 

At last the sort of practical example this thread needs!

 

I think that North Box, having pulled off his home (and starter?) has to manually pull off his distant - it doesn't happen automatically.

[LNER4479]

At last the sort of practical example this thread needs!

 

I think that North Box, having pulled off his home (and starter?) has to manually pull off his distant - it doesn't happen automatically.

Thanks. Yes, I was actually editing the post as you posted and I have now added reference to this. The perils of trying to post via a dodgy WiFi connection!