Co Acting Signals.

That reminds me - I must do a long overdue update soon.

Anyway, here's the pic for clarification:

The only purpose I can see for it is that it makes viewing of the aspect easier when looking at the monitors - though at the likes of Fulham Broadway (Eastbound), it is posible to have a small 'repeater' on top of the monitors...

I believe anywhere there are two stop signals working together at the same place on the same line, one of them has to be designated a co-acting, even if it is obvious!

After all, there can only be one actual signal in the location, and if they were both labelled as WG3 or labelled as WG3(1) and WG3(2) as some repeaters are, then technically they'd be two seperate signals which would add confusion to things like applying the rule etc.

Now I know a bit about this one, as a friend of mine was the designer for it. This was installed as part of a larger programme of SPAD mitigation measures in the late 1990s.

To be honest, most coacters are installed for that reason are they not ??

Dont even go there, noone officially knows, my Duty Manager asked me once incase I knew! Its a strange one that, asthey are both on the same side too. The only thing i can imagine is that when chesham box was open you had to have a slot for both signals to clear??

Actually, Harsig has said that the original setup with Chesham box open was that the advanced starter at Chesham was the signal slotted by the Chalfont IMR; the single line was thus under the control of the Amersham signalman, with the Chesham man only in control of the station area.

As for JT83 (originally JT25), it replaced a pair of semaphores in a similar configuration. Given that no single line token was used at the time (IIRC), it may have been felt that having a pair of line entry signals would give the driver a "second look" to ensure he was cleared for entry.

According to the Video 125 drivers eye view "Metropolitan main line", regarding the co acting signals, the "official reason as to their installation is not recorded". I await that piece of paper with pleasureable anticipation!

Id too would be interested to see the reason for the coacters, as AFAIK noone knew the reason.....

Chalfont JT 83 Co-actings.

I do not think the Co-actors replaced a similar pair of Semaphores. When the Token working was withdrawn in favour of Track Circuit Control the co-actors replaced a single Starting Signal.
Two Signals were , I think, LTE's method of giving the Driver, or Train Stop, a 'Second Chance ' to stop the train. ( perhaps they didn't trust those bumped up Neasden ER Cleaners who were let loose North of Rickmansworth.) :-)

My previous post was in direct reference to what you said on this subject several years ago. Naturally I can't remember where I read that a pair of co-acting semaphores were used.

Based on your info and what BAET and Harsig have stated I suspect the "second look" theory is the best one.

The axle counter was a much later installation (early 1990s) installed because of problems with the track circuits on the branch, principally during the leaf fall season.

Not that i am aware of. To get a second train onto the branch, you would have to authorise it past a signal or two.

ok here we go this was taken from 3rd march 1972 and if the admin would like to edit it its up to you

Mr Lawrence

Well a curious thing is, that it was on the Chesham branch and Chalfont re-signalling I first came against Mr Hadaway (chief signalling engineer). I was the drawing office man sent to work alongside him,putting right all the things that the office had done wrong in circuits. As an engineering assistant that was a formidable task, my understanding of the situation was that co-acting signals were provided because locomotive hauled trains still used the line and it was so important that the driver did not miss the aspect. If we were re-signalling the Chesham branch today we wouldn't provide these co-acting signals. Perhaps Mr Hadaway would like to add to that.

Mr Hadaway

We always had doubts about the operation of the tripcock of steam locos and this, coupled with the potential dangers of a single line, caused us to provide two signals. Whether this action ever averted a dangerous situation I wouldn't know



so theres your answer why them signals are there in the first place

Exactly the same as on an EMU or a Diesel.

A beam has to be attached and the tripcock valve attached to that with a connection to the vacuum brake.