GrahamH

56 minutes ago, phil-b259 said:

 

I was talking to a SVR loco chap the other week who was moaning about the location of the box and thought he had said it had been put somewhere different to the original with a non GWR top.

 

Is Arley the ex Wen one then?

Bridgnorth box is the wooden top from Pensnett South mounted on the brick base of the 1923 Bridgnorth box. The frame came from Windmill End box. All GWR. 

Arley box is the LNWR box from Yorton (near to Wem), with the GWR frame from Kidderminster Station box. 

(Information from the "Signalling Atlas and Signalbox Directory", Third Edition, by Peter Kay.) 

1 hour ago, Martin Shaw said:

On the matter of shunting into single line sections, I wonder whether the prohibition also applies to ScR tokenless blocks where a specific shunting token is applicable, although I think the regulations as originally drawn wouldn't have prevented two shunts meeting in the middle.

The current version of the Scottish tokenless block regulations ( no"region" in the name any more) say: "The section may be occupied outside the home signal at both ends at the same time for shunting purposes, provided the release shunting key signal has been sent and acknowledged by both signallers and the shunting keys have been obtained". 

The regulations require the signaller to tell the driver "what is to happen, in accordance with Rule Book module S5 section 3.1", which includes how far the movement can proceed. 

10 hours ago, The Stationmaster said:

I have an idea - although it's a while since I looked at the current Regulations - that the original procedure has been changed and if nothing else it  is no longer permitted to shunt onto the single line at both ends of the section.  What providing the additional Home Signal is presumably seen to do, especially with it being sited 440yds beyond an Advanced Starting Signal, is effectively make it the point at which the single line ends (although it obviously doesn't).  

Indeed it isn't permitted to shunt on to the single line at both ends of the section. A token has to be withdrawn to "permit the occupation of the single line for shunting purposes" in the current RSSB Electric Token Block regulations, and Blocking Back has been removed.

4 hours ago, The Stationmaster said:

Which as an arrangement directly facilitates the potential for a head-on collisions.  Running through trailing points, if they are not bolted by an FPL,  is unlikely to do no more than damage than to the switches and point rodding.  If however the exit points are set for a train arriving at the other end it goes exactly against the lessons of history (which are prob ably what led to the past instructions for crossing loops).

 

Surely if a train is halted before it is allowed to pass the Home Signal not only would it be less likely to pass the Starting Signal at danger than it would have been it had only been checked at the Home Signal and that signal had been cleared before the train came to a stand?  It looks almost as if someone is trying to create what amounts to a full Clearing Point where there isn't really one and has finished up with an unintended consequence as a result - if Driver is going to run through a signal ata. crossing loop of all places there's no guarantee that he/she will bring their train to a stand in the next 440 yds.  Looks like somebody didn't properly think out their risk assessment (if they did one at all?).

I'm inclined to agree. Nevertheless, I'm intrigued about the reasons why some heritage railways have gone in that direction. We can speculate as we have done, but someone must have a definitive reason. In the case of the GWR-based railways, it wasn't the norm for the GWR to interlock loops in that way. I've had a look on RSSB, but all I can find on principles of interlocking is GKTR6000, Issue 4. That is marked as "withdrawn", but provides no clues. Neither does IRSE "green book" no.2 , "Principles of Interlocking". 

As Nick C has commented earlier,  the outermost home signal wasn't necessarily provided just for acceptance purpose -  it gave operational flexibility with the provision of an advanced starter as well. So which came first? Maybe the outermost home, which then allowed the signal engineers the opportunity to install the locking described to provide what they perceived as improved safety.  But that's definitely speculation on my part!

2 minutes ago, Nick C said:

 

From what I understand, this largely depends on when they were resignalled - the concept of having both ends of the loop in correspondence is a more recent ORR requirement, as you say to prevent run-through in the event of a SPAD - but obviously isn't possible without an outer home as you'd then not have a clearing point.

That's interesting. I'd not realised that it was a requirement from the ORR. There's nothing specific in the old  ORR Guidance for Minor Railways in the interlocking requirements section (paragraphs 312 - 228). Is there anything more specific elsewhere, so far as you are aware, or was it a "local" interpretation given at the time that the railways employing this particular interlocking were signalled, maybe at the request of a particular inspector who had a "thing" about it?

In connection with the provision (or otherwise) of outer home and advanced starting signals at single line crossing places on heritage railways, probably it is worth considering the interlocking practices at some locations. For example, at some heritage installations (Toddington and Ropley I am aware of, though almost certainly there are others), the interlocking of the home signal protecting the main/loop points also requires the exit points at the opposite end to be set for the single line. I presume that this is to protect the points from being run through if a train fails to stop at the starting signal, though I do not know this for a fact. The consequence is, of course, that the simultaneous acceptance of crossing trains would not be possible as the facing points would not then be set correctly for the opposing train to run on its line to the starting signal. The consequence then is that outer homes have to be provided for acceptance purposes, and usually advanced starting signals are also provided. The clearing point is then defined as running from the outer home signal to the advanced starting signal for the opposite direction. A forest of signals, and plenty of levers for the signalman to operate!