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On 30/01/2021 at 00:07, Edwin_m said:

I think the point is that if the token was put in the pouch the wrong way round, the driver would have to take it out of the pouch to verify it.  Which may distract from other important duties such as observing the signal.  If they don't do that then one layer of defence is lost.  The interlock with the starter wouldn't prevent all possible accidents, for example if two trains were passing and the signalman gave each driver the wrong token so both starters were free.  It's then possible that he would realise the error, recover the token from the train not yet departed and in a state of flusterment replace it in the machine and accept a train into the occupied section.    

Surely checking that you have the correct token, is actually more important than checking the signal? A semaphore arm can still be checked even after you've gone past it and anyway a fleeting glance is all that's usually required. Not that I'm recommending that practice.

 

A token of the type we're talking about needs studying, which should be done before departure, certainly true of Abermule on this date.

 

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10 hours ago, phil-b259 said:

 

Yes it would!

 

Interlocking token machines with starting signals makes sure that the signals protecting the single line at BOTH ENDS must be proved to be at danger / 'on' before it is possible to withdraw a token at either end. Interlocking with token machines isn't just confined to allowing the starter to be pulled you know!

 

If you work through all the permutations, if interlocking is applied between the starting signal and the token machines then the worst that can happen is the wrong token gets carried through the wrong section. No other train can enter said section due to the interlocking so no head on collision can happen without people ignoring signals!

 

It should also be noted that for a long time it has been a rule book requirement to advise drivers that a signal is to be replaced to danger (except for emergencies) precisely because they may have been distracted by other duties and may not have noticed. However  if the signalman requires the token to be retrieved then lets be honest its going to be an unusual enough occurrence for the driver to ask why giving the perfect opportunity for the signalman to tell the driver the starting signal has been replaced to danger.

 

There also is the little matter of the Guard - so if in the scenario you have outlined, having given back the tablet the driver decides to set off past the starting signal at danger (which its going to have to be if the token machine is properly interlocked with the signals) because the signalman now wishes to accept a train rather than send one, then the Guard should activate the continuous brake and stop the train.

The sequence I was thinking of:

  • A train in each platform at B.  The train destined for A is given token for BC and the train destined for C is given token for BA. 
  • Signalman B clears starter starter towards A and this train departs, driver having failed to check the token.  Signalman B replaces starter behind this train.  
  • Driver of train destined for C realises he has wrong token and returns it to signalman B, who replaces it in machine (and replaces the starter if it had been cleared) but doesn't immediately realise the implication that a train is in section BA without the correct token.  
  • Signalman A then offers a train, which signalman B accepts.  Signalman A clears his starter, admitting a second train to the section BA.  

I agree this is an unlikely sequence of events, but it becomes less unlikely if, as at Abermule, responsibility was split between several people, none of whom had the full picture.  But as far as I can see it is possible.

Edited by Edwin_m
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6 minutes ago, Michael Hodgson said:

There's only tokens for AC if long section working is in force, and those wouldn't have been issued at B.

I think you mean in your scenario the train with  the wrong token is in section BA.

 

Yes sorry - now edited.  

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6 hours ago, Edwin_m said:

The sequence I was thinking of:

  • A train in each platform at B.  The train destined for A is given token for BC and the train destined for C is given token for BA. 
  • Signalman B clears starter starter towards A and this train departs, driver having failed to check the token.  Signalman B replaces starter behind this train.  
  • Driver of train destined for C realises he has wrong token and returns it to signalman B, who replaces it in machine (and replaces the starter if it had been cleared) but doesn't immediately realise the implication that a train is in section BA without the correct token.  
  • Signalman A then offers a train, which signalman B accepts.  Signalman A clears his starter, admitting a second train to the section BA.  

I agree this is an unlikely sequence of events, but it becomes less unlikely if, as at Abermule, responsibility was split between several people, none of whom had the full picture.  But as far as I can see it is possible.

 

But if the driver of train C (wants the token for BC section) gives the wrong token (BA section) back, the signalman will not be able to give him the right token (BC section) because one is out of the machine already! That is a pretty big wake up call for all parties and its not exactly hard to work out what has happened resulting in the request for the issue of a token BA section to be refused even though it would be possible for one to be released.

 

Ultimately you can't get away from the fact that not interlocking the starting (and ideally the home signals) at either end of the block section to the token machine significantly reduces the risk of human mistakes becoming fatal due to all the extra processes which have to happen. Granted at the time the prevailing attitudes to H&S were different, but even so its fair to say that the risks of not having said interlocking would have been reasonably obvious - alas as with all signalling the desire to not spend more than is strictly necessary (because we have a bunch of rules) plays a big part in what is deemed acceptable.

Edited by phil-b259
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49 minutes ago, phil-b259 said:

 

But if the driver of train C gives the wrong token back, the signalman will not be able to give him the right token because one is out of the machine already! That is a pretty big wake up call for all parties and its not exactly hard to work out what has happened resulting in the request for the issue of a token for section BA even though it would be possible.

 

Ultimately you can't get away from the fact that not interlocking the starting (and ideally the home signals) at either end of the block section to the token machine significantly reduces the risk of human mistakes becoming fatal due to all the extra processes which have to happen. Granted at the time the prevailing attitudes to H&S were different, but even so its fair to say that the risks of not having said interlocking would have been reasonably obvious - alas as with all signalling the desire to not spend more than is strictly necessary (because we have a bunch of rules) plays a big part in what is deemed acceptable.

Did you mean that not?

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17 minutes ago, NCB said:

Did you mean that not?

 

I meant to say...

 

But if the driver of train C (wants the token for BC section) gives the wrong token (BA section) back, the signalman will not be able to give him the right token (BC section) because one is out of the machine already! That is a pretty big wake up call for all parties and its not exactly hard to work out what has happened resulting in the request for the issue of a token BA section to be refused even though it would be possible for one to be released.

Edited by phil-b259
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1 hour ago, phil-b259 said:

Granted at the time the prevailing attitudes to H&S were different, but even so its fair to say that the risks of not having said interlocking would have been reasonably obvious - alas as with all signalling the desire to not spend more than is strictly necessary (because we have a bunch of rules) plays a big part in what is deemed acceptable.

I think it's more a case of such technology being pretty much state of the art in 1921 and a piffling little Welsh station in the middle of nowhere wasn't going to be top of the list for upgrading.  The impecunious Cambrian was probably more concerned about arrears of maintenance on the P Way  and rolling stock following WW1.  It wouldn't make much financial sense to invest while politicians your company is still under state control and the government intends to get the GWR to take it over.

Edited by Michael Hodgson
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2 minutes ago, Michael Hodgson said:

I think it's more a case of such technology being pretty much state of the art in 1921 and a piffling little Welsh station in the middle of nowhere wasn't going to be top of the list for upgrading.  The impecunious Cambrian was probably more concerned about arrears of maintenance on the P Way  and rolling stock following WW1.  It wouldn't make much financial sense to invest while politicians your company is still under state control and the government intends to get the GWR to take it over.

 

Thats still monetary considerations overriding safety considerations however you cut it.

 

But yes, I agree given the situation at the time I can see why there would be little incentive to invest.

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2 hours ago, phil-b259 said:

 

I meant to say...

 

But if the driver of train C (wants the token for BC section) gives the wrong token (BA section) back, the signalman will not be able to give him the right token (BC section) because one is out of the machine already! That is a pretty big wake up call for all parties and its not exactly hard to work out what has happened resulting in the request for the issue of a token BA section to be refused even though it would be possible for one to be released.

In my scenario the train wanting the token for the BC section never gets a valid token and remains at B.  The signalman may be distracted by the offer of a train from A or for some other reason.  

 

I agree it's unlikely, it's never happened and considering these sections are almost extinct it probably never will.  I also agree that interlocking with the starter makes an Abermule-type incident much less likely but it doesn't make it impossible.  Ultimately every system relies on people to use it properly.  

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