Revised home signals at Bank.

Green is no longer used approaching terminals on Network Rail in response to collisions years and years ago. Decades, I believe. LU uses 2-aspect signalling, it has greens into terminal platforms and has had since Moorgate.

WK700 looks to me like a pretty standard speed control signal. So what happens is if WK7 is red, WK700 will be red. As a train approaches and it enters the relevant track circuit, a timer begins. After the time has elapsed, WK700 will clear. If the train is going too fast it will pass WK700 before the time has elapsed and before it has cleared. It will therefore be tripped to a halt and will (in theory at least) not collide with any train which might be proceeding over the crossover. The timer is such that the train will have to have slowed down quite a bit before WK700 can clear. As a result, when it is allowed to proceed, it will not be able to be going that fast when it reaches WK7. Should it then fail to stop at WK7, it will be tripped to a halt before reaching the crossover and perhaps colliding with a train.

WK700 is a separate signal. With it, is WK7R - a repeater for WK7. A repeater. If WK7 is red, WK7R is yellow. If WK7 is green, ordinarily, a signal like WK7R would be green. However, by the looks of it, there is no green aspect provided on WK7R. Presumably, WK7 clears quite late, and so WK7 will never be showing green when a train passes WK700 and the repeater WK7R, so there's no need for a green aspect on WK7R. When WK700 is red, WK7R is suppressed, it doesn't show anything. When WK700 is green, WK7R goes yellow.

So a driver will approach WK700 and see a red aspect. He will slow down. When the timer has elapsed, WK700 will go green and WK7R will illuminate its yellow aspect. The driver will see green over yellow. He will proceed towards WK7 which will presumably clear as he approaches or - if it is unable to clear - when it is able to do so.

Having said that, I've just checked the Video125 driver's eye view video and it looks a lot like WK700 can clear quite early. I would have to check, but it looks to me a lot like WK700 can clear early if the crossover is locked normal and no train is using it and therefore a train can safely approach WK7 at relative speed. If, however, a train is using the crossover, the speed of an approaching train must be controlled on the approach to WK7, lest the train SPAD WK7 at speed and collide with a train on the crossover. Why bother? Why not just move WK7 back so that a train will always stop short of a crossover come what may? Well, because then a train would have to be held further away from Bank than necessary and it would take longer to berth when cleared into the platform.

Relevant related reading: LURS.

Also a pic from the Video125 film:

WK700 is indeed a "Draw up" signal protecting the converging junction ahead and the other thing I would add is that if the section ahead is occupied and WK7 is held at danger, WK700 will display BOTH yellow and red simultaneously whilst the train is travelling through the timing section and if it passes the test, the red will drop off and will just display yellow. If it fails the test, red will remain.

This is what we're taught at training, whether all draw up signals are the same, I will have to come back to you. They should be three aspect signals. They show red if the signal they are associated with is also red but when they enter the timing section, they show an additional yellow. This is the only signal type that will show a simultaneous red and yellow. When the speed is identified as being correct, the red drops off and yellow remains. As above, if the junction is clear and the semi-automatic signal shows green, the draw up signal will also be green and no timing is carried out. Draw up signals are automatic signals although their ID is based on the ID of the semi but will have three numbers always ending in zero.

Ah, I see what you're saying now As to whether all draw up signals are like this - I've seen them go from red to yellow, I've never seen them go from red to red and yellow to yellow, but you are clearly far more educated on this topic than me, so I would say most likely they are not all the same, but presumably there are/were plenty that work as you describe.

I'm not convinced WK700 and WK7R are a single draw-up signal, though. To me, it looks like a stop signal combined with a repeater, with WK700 being a speed control signal. Draw ups shouldn't show green over yellow, should they?

But if we go by the diagram, WK700 has only two aspects - red and green. The picture shot from the front seems to confirm this, although admittedly it's a little hard to see.

For the sake of comparison, there're some great pictures on the main site of the sequences at Putney Bridge, which really show this clearly. The second image, for example, is a great shot of two aspect signal WG150 and repeater RWG15, www.districtdave.co.uk/html/putney_bridge.html.

Thanks There's always more to learn!

That's not correct most speed control signals will end in a 0 but there is some which doesn't I.e EE230 circle platform Gloucester Road starter. The draw up to that is EE2300 half way along the platform.

Looks like this subject was more complex then I first thought but thanks to everyone who replied I think I understand it all - but to get back to the other question I asked I well remember after the tragic accident at Moorgate even the underground put in some yellow aspect signals before a terminus , Ongar for sure and at Chesham (at the latter place still today ) in fact I thought it was a legal requirement that's why I asked ? I know British Rail adopted it, so the whole subject must have been reviewed at some point for the underground when new technology became available ? unless I am wrong.

There used to be a few yellow lights going into the siding at Liverpool Street on the Central Line don't know if they still there not worked on the Central since the resignalling in the late 90's

Having said that, I've just been watching Video125's driver's eye view video of the Metropolitan Main Line, filmed in 1995 and I noticed that the yellow signal the train passes on the approach to Chesham station is actually plated A1000 and presumably did show danger when passed by the Chesham train. I don't know if it's still there and still plated like that, it might be.

I'm really not an expert, but it doesn't seem to have any kind of speed control or ability to hold trains, in fact, it does not even seem to have a trainstop, and I think it basically exists to serve the same function as a fixed repeater or, say, a fixed distant board, but all the same, you definitely have a point about Chesham

Quite right - the aspect sequence only needed to change where there was multiple aspect signalling. As LU could only show a red or green previously there was felt to be no need to change the green to a yellow.

Various signals in the tunnel at Camden Town had the air delay until the end. Was something to beware of if both the draw-up and its associated signal cleared together as there was a risk of motoring before the red had extinguished on the draw-up.

G.340 and G.350 at Golders Green also had a delay and period of dual aspect, however this was done by means of relays.

Signals don't have an amber aspect, they show yellow <pedant>. traffic lights show amber.

While I can't comment on the current set-up at Bank I worked on there in BR days and was involved driving the test trains into Bank when the "Moorgate" signalling was installed. I had to try at all speeds up to 18 mph over the crossover into Bank to make sure the apparatus did what it was designed to do. It did; however, when tested at about 20mph (ahem) the train bounced sideways a bit and although the train stop was raised, the train didn't trip as it rolled sideways! the cure was a word in the ear and told "don't bloody well be a count and exceed the speed limit" or similar words!

It was possible when going into the straight ahead platform to stop with the buffer block on the train bouncing forward on its spring and leaving a nice greasy oblong on the buffer stop. when you looked, the train was actually 2" from the blocks and still an inch way from the train stop. Ian, the signalman used to keep wondering who'd hit the blocks as the "hit the blocks" warning never sounded. Hehehe.

Out of interest, if WK7 is cleared early, do you nevertheless get a yellow on WK7R, or does it simply show no aspect? Or do you get a green as you would expect, only the fine diagram on harsig's website seems to show no green aspect on WK7R?

Although, I ask that, I wonder if it's possible for the signaller in Waterloo control room to clear WK7 early, I'm guessing the signalling computer wouldn't clear WK7 until a train was on the approach, or have I got that wrong?