MAS to Semaphore boundary

[Pete2210]

Going from 4 aspect MAS  to a semaphore signalled area I think that the last colour light signal should only show Red/Yellow/Double Yellow. can anyone tell me whether that is right or should the last colour light be just a Red/Single Yellow.

 

Thanks

 

Pete 

[The Stationmaster]

Depends entirely on the distance between signals and what sort of semaphore follows the final colour light signal as well as the distances involved.  Thus :-

 

1. Colour light to semaphore distant which is out at full braking distance -the c.l. need only show red or green,

 

2. If the braking distance from the semaphore distant is too short then the final c.l. will be sited to take account of that and would show red. double yellow or green (and it if reads to a stop signal with a lower arm distant it would also be able to show single yellow).

 

3. If it reads to a semaphore stop signal (most probably only found in stagework) it would most likely show red, single yellow or green - the green being in effect the distant 'off' for the next signalbox in advance.

 

But practice varied between BR Regions, practice - even within particular Regions - changed over the years and what was done on stage work was often very different from permanent jobs

[Pete2210]

Thanks Stationmaster,

 

That does unmuddy the waters a bit! the distance to the next stop signal would be in the region of eight (real) feet and I was thinking of putting a Distant signal in in advance of the last colour light, so your no.2 suggestion seems to cover my question nicely, thank you very much Mike.

 

Pete

[DavidBird]

I've been using the diagram of the Trent PSB resignalling, available from the Signalling Records Society here http://www.s-r-s.org.uk/archivesignals/brmr/1969-2810g.pdf

 

On that diagram there are various CL signals that lead on to older signalling.

 

For example TT245 is the last signal (a 3-aspect R/Y/G) on the route from Nottingham to Newark before the Grantham line branches off at Netherfield Jn.  It is labelled "Also acting as Netherfield Jn Down Midland Distant 850 Yds from NJ3".  Similarly TT323 (3a RYG) is "Also acting as Lincoln St Crossing Down Goods Distant 1030 Yds from LS4"  However in both of those cases they lead on to 3a CL signals, but controlled by different boxes, and seemingly semaphore replacements.

 

At Pye Bridge Jn, there is TT87 (4a+pos4 feather) which is "Also acting as Sleights Sidings East Down Distant 1042 Yds from SE15" where SE15 is also a 3a RYG; but further down the line there is SE14 (3a RYG) leading onto SE13 (twin arm semaphore home and distant).

 

Around Blackwell there are examples of Trent MAS CLs leading onto semaphores, and also semaphore distants leading onto 3a and 4a MAS Trent signals.

 

In all of the maze of main lines and coal branches in the area around 1969, there is not a single example of MAS CLs leading onto seperately-controlled semaphores on plain line!

 

Check out these diagrams (they're free to download - I've donated!) and some of the other areas, they'll give you ideas of what happened.

 

Now a question for Mike Stationmaster.

 

Depends entirely on the distance between signals and what sort of semaphore follows the final colour light signal as well as the distances involved.  Thus :-

 

...

 

2. If the braking distance from the semaphore distant is too short then the final c.l. will be sited to take account of that and would show red. double yellow or green (and it if reads to a stop signal with a lower arm distant it would also be able to show single yellow).

 

...

 

I assume that the semaphores are left from older signalling schemes.  If so in what case would the braking distance be too short?  I always thought the point of a distant was to give a warning the home was On at an adequate braking distance...

[phil-b259]

While not directly answering your question, In Southern days the situation when moving from  semaphore to MAS was that the final semaphore stop signal had its green lens removed and a two / three aspect colour light head fitted below it. If the semaphore was at danger the red light in the semaphore would be lit with the arm horizontal while a proceed would use single / double yellow / green) light in the the colour light head along with the semaphore arm being at 45 degrees.

 

2. If the braking distance from the semaphore distant is too short then the final c.l. will be sited to take account of that and would show red. double yellow or green (and it if reads to a stop signal with a lower arm distant it would also be able to show single yellow).

 

I am confused

 

The question is what principles apply to the yellow aspect on the final colour light signal because a single yellow aspect on MAS and a semaphore distant carry very different meanings. A single yellow MAS tells the driver the condition of the next stop signal while a distant merely tells the driver that one or more stop signals ahead are at danger.

 

Thus one possability must be that in this situation of MAS to semaphore (if the semaphore is a stop signal then the final colour light a 3 aspect red / yellow / green) if said  colour light is at yellow, does the colour light say to a driver 'the next stop signal is at Red' or does it mean 'any one of a number of semaphore stop signals ahead are at danger? (though I appreciate they do both require the driver to slow down at the same rate)

 

However I can see that if the first semaphore stop signal also had a distant arm fixed below it then your final colour light might have a double yellow aspect.  In this scenario a double yellow would tell the driver the next semaphore stop signal is showing a proceed but the semaphore distant is still at caution (effectively the next semaphore signal is displaying a single yellow in MAS terms).

[DavidBird]

phil-b259, on 20 Jul 2013 - 11:40, said:

 

I am confused

 

The question is what principles apply to the yellow aspect on the final colour light signal because a single yellow aspect on MAS and a semaphore distant carry very different meanings. A single yellow MAS tells the driver the condition of the next stop signal while a distant merely tells the driver that one or more stop signals ahead are at danger.

 

Thus one possability must be that in this situation of MAS to semaphore (if the semaphore is a stop signal then the final colour light a 3 aspect red / yellow / green) When at yellow does the colour light say to a driver 'the next stop signal is at Red' or does it mean 'any one of a number of semaphore stop signals ahead are at danger? (though I appreciate they do both require the driver to slow down at the same rate)

...

 

DavidBird, on 20 Jul 2013 - 11:28, said:

 

...

 

At Pye Bridge Jn, there is TT87 (4a+pos4 feather) which is "Also acting as Sleights Sidings East Down Distant 1042 Yds from SE15" where SE15 is also a 3a RYG; but further down the line there is SE14 (3a RYG) leading onto SE13 (twin arm semaphore home and distant).

...

 

I would have thought that as (for eample) TT87 is noted as "Also acting as Sleights Sidings East Down Distant" , when showing single yellow with feather, it means  one or more of SE15, SE14 or SE13 are at stop, but when just showing single yellow (no feather) it means TT79 is at red.

[Grovenor]

I am confused

 

The question is what principles apply to the yellow aspect on the final colour light signal because a single yellow aspect on MAS and a semaphore distant carry very different meanings. A single yellow MAS tells the driver the condition of the next stop signal while a distant merely tells the driver that one or more stop signals ahead are at danger.

 

A distant tells the driver that the first home signal at the box he is approaching is at stop, essentially the same as a single yellow on MAS. You are forgetting rule 39A.

 

The transitions from MAS to Semaphore were defined in BR Signalling Principle 22 when the '60s resignalling was in build, most of the concerns dealt with relate to the semaphore to MAS transition rather than the MAS to Semaphore, see attached.

Regards

Keith

 

Principle-22.pdf

[The Stationmaster]

I've been using the diagram of the Trent PSB resignalling, available from the Signalling Records Society here http://www.s-r-s.org.uk/archivesignals/brmr/1969-2810g.pdf

 

On that diagram there are various CL signals that lead on to older signalling.

 

For example TT245 is the last signal (a 3-aspect R/Y/G) on the route from Nottingham to Newark before the Grantham line branches off at Netherfield Jn.  It is labelled "Also acting as Netherfield Jn Down Midland Distant 850 Yds from NJ3".  Similarly TT323 (3a RYG) is "Also acting as Lincoln St Crossing Down Goods Distant 1030 Yds from LS4"  However in both of those cases they lead on to 3a CL signals, but controlled by different boxes, and seemingly semaphore replacements.

 

At Pye Bridge Jn, there is TT87 (4a+pos4 feather) which is "Also acting as Sleights Sidings East Down Distant 1042 Yds from SE15" where SE15 is also a 3a RYG; but further down the line there is SE14 (3a RYG) leading onto SE13 (twin arm semaphore home and distant).

 

Around Blackwell there are examples of Trent MAS CLs leading onto semaphores, and also semaphore distants leading onto 3a and 4a MAS Trent signals.

 

In all of the maze of main lines and coal branches in the area around 1969, there is not a single example of MAS CLs leading onto seperately-controlled semaphores on plain line!

 

Check out these diagrams (they're free to download - I've donated!) and some of the other areas, they'll give you ideas of what happened.

 

Now a question for Mike Stationmaster.

 

 

I assume that the semaphores are left from older signalling schemes.  If so in what case would the braking distance be too short?  I always thought the point of a distant was to give a warning the home was On at an adequate braking distance...

It does depend on providing adequate braking distance.  Different Regions tended to do it different ways but in most cases the braking distance from the semaphore distant would be the crucial bit (I say in most cases because in some instances a double yellow was used if the semaphore distant in advance was at caution  (i.e. effectively showing a single yellow) in order to provide additional braking distance; in other words when showing a proceed aspect the c.l signal was actually functioning as an Outer Distant).

 

On the WR it was either usually a case of the last colour light showing no more than red or green when reading towards a distant although it was not unusual on stage works to find a 3 aspect signal acting as the distant for the semaphore signalled 'box in advance.

 

The important thing to remember in transitions like this is that the c.l.signal would be functioning as a distant signal and not in accordance with normal m.a.s. principles - therefore it would only clear to green when all stop signals applicable to that line at the 'box in advance were 'off'.  But i wouldn't mind betting that in some cases - where there was no direct lever control from the 'box in advance - the proceed aspect worked on m.a.s. principles instead of as a distant.  I've an idea lurking in the back of my mind that this sort of thing was criticised because the inconsistencies it could create;  It could be very misleading if a Driver treated the signal as a distant when in fact it was working to aspect sequence because he could run out of braking distance very easily in such conditions.

[phil-b259]

A distant tells the driver that the first home signal at the box he is approaching is at stop, essentially the same as a single yellow on MAS.

 

Not as far I have been taught its one of the things that was made quite clear to me in my basic mechanical signalling training in Derby. The 1955 rule book describes distant signals thus:

 

"Rule 36A :- Distant signals are placed in rear of stop signals to which they apply."

"Rule 36B :-Where only one distant signal is provided for a diverging junction such a signal applies to all trains approaching it."

"Rule 36C :-The caution position of a distant signal indicates to a driver that he must be prepared to stop short of any of the stop signals to which it applies"

 

Note the use of the plural term; stop signals

 

A distant semaphore signal applies to all semaphore stop signals in the direction of travel worked by a single box. In this respect it is quite categorically not the same thing as a single yellow aspect under MAS. While in some places there might only be a single stop signal to which a distant may apply, such as an intermediate block post, in others there may be an outer home, inner home, starting and advanced starting signals - all of which must be 'off' before the distant can be cleared. Yes there are such things as outer and inner distant signals but these are only installed in busy areas and each distant can still cover more than a single stop arm. Further confusing the issue of course is that in some locations the distant signal itself may have been moved or replaced by a two aspect green / yellow colour light. At first glance this can give the impression of a MAS area where red / green colour lights and yellow / green repeaters have been installed but despite looking similar the two setups give drivers different information. A yellow / green colour light repeater signal will tell the driver the state of the next stop signal only. A yellow / green colour light 'distant' signal will however apply to a number of subsequent stop signals.

 

For example

 

Mechanical                                                        

 

Distant            =  Y ('on')      OR     = Y ('on')     OR     = G ('off')

Home Signal    = R ('on')                = G* ('off'*)              =G ('off')   

Starting signal = R ('on')                 = R ('on')               =G ('off')

 

MAS

 

2 aspect Repeater            =  Y       OR     = G       OR      = G

3 aspect Signal                 = R                  = Y                  = G   

2 aspect Signal                 = R                  = R                  = G

 

* Rule 39A should be applied here unless box instructions specify otherwise

 

You are forgetting rule 39A.

 

 

Rule 39A as far as I know it describes the manual application of what we now call 'approach control' to stop signals. The 1955 rule book describes it as

 

"Rule 39A :- Where a stop signal is at danger the stop signal next in rear of it and worked from the same signal box must not be lowered for an approaching train until it is close to such a signal and has been bought quite or nearly to a stand"

 

Nothing in there about distant signals however assuming rule 39A is in place then depending on the number of signals the distant covers then it might be the case that the distant does look as though it only apples to the first stop signal.

 

If you look at the table above then because there are only two stop signals, if the second one (the starting signal) remains 'on' then under rule 39A the signalman cannot clear the home signal to 'off' until the train is approaching it and thus the distant signal does look as if it is behaving like a single yellow MAS signal. However if the home signal is exempt from rule 39A and the distant signal remains 'on' here is nothing to tell the driver whether its the home or the starting signal that is 'on'  a situation that simply cannot exist under MAS.

[DavidBird]

In what sort of situations would a Home (semaphore) signal be exempt from Rule 39a?

[TheSignalEngineer]

Sometimes where a passenger train was booked to stop at a station, e.g. terminating for a turn-back. We also had a couple in our area where it was to keep freights moving as long as possible on a rising gradient when waiting for a line clear. They were listed in the Sectional Appendix. 

[The Stationmaster]

Sometimes where a passenger train was booked to stop at a station, e.g. terminating for a turn-back. We also had a couple in our area where it was to keep freights moving as long as possible on a rising gradient when waiting for a line clear. They were listed in the Sectional Appendix. 

Agree exactly regarding the principle behind these examples cited by SE - the usual exemption was where there was a reason to keep trains (sometimes only certain classes of train) moving for as long as possible.  Or where - as in the example quoted of a passenger train stopping/terminating - the train would not be going beyond the next stop signal in advance in any case.  On the Western there was always a very strict and carefully considered granting of Rule 39a exemptions and as a result it was unusual to find one.

[DavidBird]

I would have thought that as (for eample) TT87 is noted as "Also acting as Sleights Sidings East Down Distant" , when showing single yellow with feather, it means  one or more of SE15, SE14 or SE13 are at stop, but when just showing single yellow (no feather) it means TT79 is at red.

 

I've just checked my copy of the Sectional Appendix for 1980, the line from Pye Bridge Jn to Sleights East LC is actually code A - Track Circuit Block on Goods Lines, hence my comment about the aspects at TT87 is wrong.  TT87 showing yellow and feather means SE15 is red. Thus SE15 is a conventional 3a MAS, and SE14 (3a) is the transition signal, leading onto SE13 semaphore stop signal.

 

At Westhouses & Blackwell, TT65 is a 3a with sub and theatre indicator, leading to TT58 on the down (bi-directional) goods line, and TJ24 and TJ23, semaphore home and starter for Tibshelf East Jn signalbox, lines worked by Permissive Block.  I believe that TT65 with yellow would mean TT58 is red, but yellow with junction indicator would mean one or both TJ24 and TJ23 are at stop (of course also applying rule 39A...)