Diagram - Edgware Rd cabin

Don't know if this may help you www.flickr.com/photos/nickstransportpics/6601530051/in/photostream/

Fixed Red Light.

Basically what it says on the tin. They're used in sidings and at terminal stations and places to provide a nice bright warning of the end of the line. They're also used to denote other points which trains must not pass. For example, in this instance, I assume the FRL is there to denote the limit of the wrong road shunt move into platform 1 from the main line. Passing the FRL will obviously have you travelling in the wrong direction along the eastbound/outer rail line. LU also got into a habit a while ago of providing them at stations where trains can reverse, at points where trains should not reverse. For example, I am given to understand that there is one at the east end of Dagenham East westbound platform 1. Now trains can reverse at Dagenham East westbound, but the correct procedure is to shunt forward, out of platform 1, along the westbound, to the limit of shunt, change ends, and shunt over to platform 2 via shunt signal FG18 and main running signal FG22. The FRL protects against somebody getting muddled up, changing ends in the platform, and expecting to head east over a trailing crossover, much as at East Ham, for example.

Except that the incident which prompted their installation actually occurred at Kings Cross on the Piccadilly line. This was some 17 years prior to the Camden Town incident. The fixed red lights were only provided at reversing locations and since Camden Town is not a reversing location no fixed red lights were provided there under the programme of installation. The RAIB report into the Camden Town incident refers to the Kings Cross incident in paragraph 75.

You do?

How interesting, I thought that shunt signals only gave authority to proceed as far as it was clear, but shunt signals can be used in many layouts to allow routes not possible by normal signals so I suppose it is not unique.

That is normal for fibre optic shunts with an associated colour light signal or FRL.


What do you find unusual about the X signals and draw-up arrangement?

X400 is an X signal for a different reason to the other 3. IIRC it is something to do with the tunnel ventilation system on the T5 extension. X399(?) on the eastbound road is an X signal for the same reason as X400. There are 6 consecutive X signals on the eastbound H&C beginning with the starter at Westbourne Park.

I'm struggling to think of 5 'varieties' of "X" signal on the Picc:

As you mention there is the 'last (or almost last) automatic signal before a controlled area' type - such as WRX443.

Floodgate type - e.g. FPX777.

And various plain Xs such as X400, which are designated as such for a variety of (often unique) reasons.

The only other types that spring to mind are Track replacement (TRX - none on the Picc that I can think of) and Possession (PNX - which is a temporary designation as part of protecting a possession). The only two TRXs I can think of are the eastbound starter at Westbourne Park and the Westbound starter at Royal Oak. PNX signals wouldn't normally be seen by a line-based t/op or i/op.

Ah - well if you're counting the various different reasons for non-prefixed X signals then I would suggest there's 6 'varieties' on the Picc, because (as I mentioned) X402a/b/c are Xs for a different reason to X400 (and X399).

PiccNT The old signal system you mention was known as metal micky it had less memory than an old spectrum computer consul

Shunt signals associated with a running signal (even if that running signal is a Fixed Red) should always be suppressed if they have not been cleared for the shunt move. It's the same on the Central ljne and a few other places which use fibre optics.

As for the four X signals in a row, try the C&H around Paddington' all of which are associated with different things:
TRX123, X125, X127, X129, OPX131, OPX133 (EB)
The Westbound is similar but one 'A' signal in the island: X134, X130, A128, TRX126.

TRX123, X125 and TRX126 relate to the detection of the Royal Oak crossover
X127, X129 and X130 relate to the detection of the Paddington crossover.
OPX131 has a hold facility controlled by Edgware Road
OPX133 is a 'traditional' X signal approaching a controlled area.
X134 is associated with a Track Circuit Interrupter associated with Network Rail platform 14 at Paddington.

Correct