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Inter-Signal Box Communication


Thos

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Imagine two lines from A and B joining at C then to D and E where two lines split to F and G.

There are two local passenger trains scheduled (same lamp codes):  from A to G arriving at C at 0905 and B to F arriving at C at 0910.

 

The 0905 is delayed and C receives a request from B for the 0910.

 

Q1 - Does C accept the train from B or wait for the delayed 0905?

 

Q2 - If C accepts the train from B, how is E told that the train is bound for F and not G?

 

Q3 - What does the driver of the 0910 do if he gets to E and is signalled to go to G?  Does he stop or follow the line to G?

 

Would the answer be different in 1890 from 1935? (i.e. would the boxes be in telegraph or telephone communication) and would the system vary between railway companies?

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It all depends - on lots of things.  Firstly how late is the train which is running late, secondly are there any particular agreements in place regarding timetable order or any other priorities?

 

However let us assume that the 09.10 will precede the 09.05 and that is acceptable.  The Signalman at C offers it forwards and sends  a boxer (box-to-box message) '09.10 preceding 09.05' - in the past that might well have been done by telegraph or it could be done by telephone.  Depending on the Company and route by 1935 it still might have been done the old way, i.e. by telegraph message.

 

Equally it might be the case that there is a route bell code for one or other, or both, of the trains; so there is no need for the boxer - the 'Is Line Clear? bell code supplements the 3-1 with something else and that immediately identifies which route the train is for.

 

As far the Driver is concerned things are equally simple - if he is wrongly routed he must stop short of the junction signal and advise the Signalman that the route is incorrectly set (unless the junction is specifically identified in the Appendix as, in effect, one where taking either route is acceptable provided the train itself could take either route and still make its booked stops etc).

 

And it really is all as simple as that.

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Agree with Mike on this in that it can vary in accordance with local regulations and also - back between 1890 - 1935 - by company.  

 

Let's say the lines to A, F and G are operated by the Main Line Railway and that to B by the Little Nuttingford Railway.  The signalmen at both junctions are in the employ of the MLR and standing instructions are to offer priority to their own trains.  When offered a train by the LNR signalman at B while expecting one from his MLR colleague at A and having to make a decision the signalman at C might telegraph / phone A to enquire where that train is.  If it is within 10 minutes of right time he may still accord it priority delaying the"rival" train by perhaps 5 minutes.

 

Such a situation occurred at Exeter where the GWR signalmen would delay the SR trains given half a chance and allow their own a clear road.

 

If it were today however with delay attribution required the signaller (note the updated jargon for "today" ;) ) at C must decide, having regard to the overall operation, whether to hold the train from B by a few minutes which it might recover and allow the late-runner from A a good run or whether to allow the train from B an unchecked run while potentially adding to the delay of the train from A and copping "attribution" for that delay.

 

Are the two trains timetabled to make connections with each other?  If so and if the late runner is only a little late then it may still be allowed to go first to maintain the timetabled connection rather than lose it for the sake of a few minutes and incur the ire of passengers and possibly the cost of alternative transport being provided.

 

Those are just a few examples of how and why operating practice may vary.

 

In every case of an incorrect route being offered the driver must stop and communicate with the signalman.  In most cases a phone is now provided but before that it sometimes meant a hike to the box if it wasn't a signal in the immediate vicinity.  The driver may not sign the road incorrectly offered and thus be unable to take the train that way even if it is being diverted for some reason previously not advised to him.  Or the loco or rolling stock may be prohibited from the route offered.  Again it's not as simple as just "going the other way" as situations differ.  

 

Not every occasion is a signalling error.  I was once on a railtour which stopped in front of a yellow-with-feather signal while we watched the driver climb down and phone the bobby.  The aspect went red and we had to wait the required safety period of a couple of minutes before it then turned green with the feather gone.  The train was advertised (to patrons and in the STN) as taking a curve which it was banned from using.  The driver spotted the error knowing that he was not permitted to take the left diverge offered with the stock in question.  Of course we were miffed that we missed a rare curve (for which purpose many of us were on board) but right was on the driver's side.

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If it were today however with delay attribution required the signaller (note the updated jargon for "today" ;) ) at C must decide, having regard to the overall operation, whether to hold the train from B by a few minutes which it might recover and allow the late-runner from A a good run or whether to allow the train from B an unchecked run while potentially adding to the delay of the train from A and copping "attribution" for that delay.

That should be covered on the Level 1 Regulating Statement - the decision does not normally rest at signalbox level but would have been agreed in advance between NR and the relevant operators.  The usual procedure has normally been to try to maintain timetable order and to specify margins allowed to maintain that or to allow it to be broken.

 

Yesterday I saw an empty stone train put across in front of two HSTs at Reading so someone, or something in the electronics, was either trying to maintain timetabled order or was having a very bad day  (as it was the Reading layout's swansong day I believe the spirit of the good old Reading panel crazy gang must have been having his final dabble).

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Generally at junctions the box was at or relatively close to the Jcn so the fireman might walk over or a few blasts on the whistle might alert the Signalbox and after a few gestures the road replaced. Not necessarily per the rule book but it worked.

SPT's signal post telephones shortened the walk for crews and nowadays there are a choice of onboard train radios depending on area but shortly there will be just GSMR or personal mobiles. ;)

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In  about  1956  I  was  on  a  Cathcart  Circle  train  from  Glasgow  Central.  This  takes  the  right  hand  road  at  Eglinton  Street.  As  we  trundled  along,  suddenly  an  emergency  stop  at  Eglinton  Street.  On  looking  out  of  the  window ,  the  loco  and  first  coach  were  down  the  left  hand  (Rutherglen)  road,  proprerly  signalled,

 

There  was  a  good  deal  of  shouting  between  the  Loco  and  the  box,  which  I  couldn’t  hear,  being  at  the  rear  of  the  train,  and  after  a  few  minutes  we  reversed  back  clear  of  the  points  and  the  junction  signal.  After  a  proper  interval  the  signal  cleared  for  the  Cathcart  Circle  (right  hand)  road,  and  off  we  went.

 

I  doubt  very  much  whether  any  of  this  was  officially  recorded,  but  it  does  show  that  the  old  railways  didn’t  always  go  by  the  book.

 

Allan  F

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In  about  1956  I  was  on  a  Cathcart  Circle  train  from  Glasgow  Central.  This  takes  the  right  hand  road  at  Eglinton  Street.  As  we  trundled  along,  suddenly  an  emergency  stop  at  Eglinton  Street.  On  looking  out  of  the  window ,  the  loco  and  first  coach  were  down  the  left  hand  (Rutherglen)  road,  proprerly  signalled,

 

There  was  a  good  deal  of  shouting  between  the  Loco  and  the  box,  which  I  couldn’t  hear,  being  at  the  rear  of  the  train,  and  after  a  few  minutes  we  reversed  back  clear  of  the  points  and  the  junction  signal.  After  a  proper  interval  the  signal  cleared  for  the  Cathcart  Circle  (right  hand)  road,  and  off  we  went.

 

I  doubt  very  much  whether  any  of  this  was  officially  recorded,  but  it  does  show  that  the  old  railways  didn’t  always  go  by  the  book.

 

Allan  F

I did much the same at Herne Hill in south London where the signalman gave me the wrong route and I took it. It wasn't until I got to the points that I noticed something was wrong as we started off down the diverging route. I got round the corner and stopped at the first signal where I got on the phone. The signalman told me that i could change ends and there was a dummy behind me that would take me back into the platform where we could have another go. Nothing was reported to management and we got away with it...

 

 

...until a few weeks later when I went to a rehearsal with some mates in a band and the lead singer asked me what had happened at Herne Hill? His girlfriend had been on the train and seen me...

 

Andi

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Same thing happened to me when I was travelling on an HST from London to Nottingham that took the Derby line at Trent.  It was a one of the few through workings to Sheffield/Leeds that were routed via Nottingham so I think the signalman just saw the E in the headcode and forgot.  The divergences are of equal speed and the principles for colour light signalling at the time did not allow for any advance warning of the route to be taken.  The train pulled up at the next signal and after a phone call set back over the junction.  This one maybe not so easy to cover up, as someone probably noticed when it was 10-15min late into Nottingham. 

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