Signals now on the central line.

[naz]

Hi-When the central line was re-signalled in the early nineties I must admit I only took a slight interest in it however just recently I have taken more interest it, much has been written in the pages of this forum and elsewhere on the ATP side of things  but little about the colour light signals . From what I have  already read and seen from the train window and standing on the station platforms main running signals are either two aspect red & green and three aspect red, white & green.. Now green on either signal means line clear as far as the next signal ? while white means a train might be brought to a stand at a block marker board between two signals ? So a two aspect signal has no block marker boards ahead of it true or false ?so what is the criteria for installing two or three aspect signals at specific locations or the number of signals that may be between two stations ,if anyone would like to add to or correct anything here please do I would like to know more.  

[Deleted]

Kind of.

Green on either signal means that the line is clear until the next colour light signal. As a result, a train in RM, which will not be picking up codes, may proceed past the signal as the entire line is clear to the next signal. That signal, of course, will be at red or white if a train is ahead and the train in RM can be brought to a stand at that signal, thus keeping trains safely apart even in the case of ATP failure.

A red means target speed of zero, do not pass the signal as there is a train ahead and it is not safe to proceed for any train, RM or not.

White means the line is not clear to the next signal - there is a train between this signal and the next. However, the required number of blocks are clear and the target speed is greater than zero. As such a train in Coded/Auto may proceed, because it's picking up codes and the ATP can bring it to a stand short of the next train. Yes, indeed, the train will come to a stand at a block marker board if the train ahead does not move out of the way in time, but there is no requirement for a train to stop at a block marker board after passing a white signal unless the ATP commands it due to a train ahead. Trains in RM may not proceed, because there is a train between this signal and the next. With no codes, the driver will have no way of knowing where that train is. As such, if the train ahead does not move, the only way a driver will be able to stop safely is by observing it out of the window and stopping in time. Now, the train is limited to 18 kph in RM so this seems like it should be possible (and, indeed, the procedure for passing a signal at danger calls for RM) but it is obviously better and safer to wait for a green if the signal is working correctly as that guarantees the line is clear until the next signal and there is no risk of a collision.

There almost always is at least one block marker board between a two-aspect signal and the next colour light signal. For example, between 2-aspect signal WOO 7254 (starter from westbound platform 1) and 2-aspect signal WOO 7252, there are two block marker boards - WOO A7354 and WOO A7356, used for enforcing speed limits on trains as they proceed through 21 road and checking their speed down as they approach WOO 7252.

[stapler]

I know what RM means,but what does RM actually stand for?

[Deleted]

Restricted Manual

[Tom]

From memory, the white aspect on the Central Line means that at least two code blocks are clear. Thus if you have another signal at the end of the second code block the need for a white aspect is removed.

[Deleted]

Apr 7, 2016 13:41:58 GMT Tom said:

From memory, the white aspect on the Central Line means that at least two code blocks are clear. Thus if you have another signal at the end of the second code block the need for a white aspect is removed.

This is almost certainly the general rule, although I believe the starter at Roding Valley inner rail (WOO 7278) can show white with the track clear to the next block marker board (WOO A7210) plus track circuit 7212 clear, which obviously serves as an overlap. However, I don't believe there is any other block marker board or signal until WOO 7276, which is at the end of 7214 track circuit. (A green on WOO 7278 requires the track clear to WOO 7276 and track circuit 7216 clear.)

---

Something I've been meaning to ask for a while. On the Video 125 driver's eye view, we see a signal in the pipe between Leyton and Stratford which appears to be showing a yellow aspect on the video. Does/did it really show yellow? And if so, why?

[Deleted]

I know this thread is a few months old but I've just joined.



There is no yellow light between Leyton and Stratford.

[bananaman]

Jul 9, 2016 22:23:14 GMT @kingsiwel said:

I know this thread is a few months old but I've just joined.



There is no yellow light between Leyton and Stratford.

There is an RGI repeater in that area (it's like a standard RGI but with three yellow aspects instead of red) but a driver would never normally see it lit.

[Deleted]

Jul 10, 2016 6:31:33 GMT bananaman said:

Jul 9, 2016 22:23:14 GMT @kingsiwel said:

I know this thread is a few months old but I've just joined.



There is no yellow light between Leyton and Stratford.

There is an RGI repeater in that area (it's like a standard RGI but with three yellow aspects instead of red) but a driver would never normally see it lit.

There is, that's a good point, but in this case I was thinking of this



It's hard to capture the full effect, but it looks distinctly yellow on the video, and actually unlike other white signals which can be seen.

Here's an example where it's a little more obvious:



Now compare this with the starter at OXO E/B



Still, it's interesting, maybe it's a weird camera effect, what with the lighting and all, I certainly had to take more than one screenshot to get the full yellow effect, there were stills where it didn't look that yellow. Or maybe they've simply changed it since. Thanks @kingsiwel and welcome! And good luck in your new role

[up1989]

Can a Train in CM/Auto pass a station starter signal at danger? I know In the seltrac system on the northen line you can't proceed in PM/AUTO until your target advances, does anyone know if its the same for central line?

[Deleted]

On when a white aspect is shown

[trainopd78]

The "yellow" aspect is just a dirty signal lens.

You can overrun a signal (SPAD) in coded with the trains emergency brakes coming on as soon as you enter the next section. The ATP puts the brakes on if sitting at a red signal for a certain period (sorry cant remember the exact time - got 60 secs in my head by probably wrong) so the train wont then move until it receives a code to proceed. Theres a bit more to it but thats the basics.

[Deleted]

Jul 10, 2016 19:02:30 GMT trainopd78 said:

The "yellow" aspect is just a dirty signal lens.

Ahhh that makes sense, thanks for clearing that up I thought it might have just been an esoteric or experimental installation.

[hobbayne]

Jul 10, 2016 19:28:30 GMT tut said:

Jul 10, 2016 19:02:30 GMT trainopd78 said:

The "yellow" aspect is just a dirty signal lens.

Ahhh that makes sense, thanks for clearing that up I thought it might have just been an esoteric or experimental installation.

Even to this very day it still appears to be yellow, and the DEV Video was filmed in July 2011!

[Deleted]

Jul 10, 2016 22:07:43 GMT hobbayne said:

Jul 10, 2016 19:28:30 GMT tut said:

Ahhh that makes sense, thanks for clearing that up I thought it might have just been an esoteric or experimental installation.

Even to this very day it still appears to be yellow, and the DEV Video was filmed in July 2011!

Back before the refresh of the front cabs, when it was mostly dark grey, before the new, simpler panels were installed with lots of red.

[drainrat]

Jul 10, 2016 19:02:30 GMT trainopd78 said:

The "yellow" aspect is just a dirty signal lens.

You can overrun a signal (SPAD) in coded with the trains emergency brakes coming on as soon as you enter the next section. The ATP puts the brakes on if sitting at a red signal for a certain period (sorry cant remember the exact time - got 60 secs in my head by probably wrong) so the train wont then move until it receives a code to proceed. Theres a bit more to it but thats the basics.

It all depends on the location, some places you can hear the ATP drop out almost immediately, other places it doesn't drop out at all no matter how long you're sat there. train can move at any time!

[drainrat]

Jul 10, 2016 6:31:33 GMT bananaman said:

Jul 9, 2016 22:23:14 GMT @kingsiwel said:

I know this thread is a few months old but I've just joined.



There is no yellow light between Leyton and Stratford.

There is an RGI repeater in that area (it's like a standard RGI but with three yellow aspects instead of red) but a driver would never normally see it lit.

Been so long I looked but isn't the RGI on approach to the tunnel?

[Deleted]

Aug 24, 2016 8:53:25 GMT drainrat said:

Jul 10, 2016 6:31:33 GMT bananaman said:

There is an RGI repeater in that area (it's like a standard RGI but with three yellow aspects instead of red) but a driver would never normally see it lit.

Been so long I looked but isn't the RGI on approach to the tunnel?

It is, just before the bend round to the left.

[drainrat]

Aug 24, 2016 10:35:47 GMT @kingsiwel said:

Aug 24, 2016 8:53:25 GMT drainrat said:

Been so long I looked but isn't the RGI on approach to the tunnel?

It is, just before the bend round to the left.

That's right, it was the first gap on the Central line they widened so it couldn't be bridged. ATO doesn't recognise an RGI so the likelihood of bridging was high, to ensure no bridging they widened the gaps, so all TC gaps on Central line are now over 40ft wide.

[drainrat]

Jul 10, 2016 14:31:12 GMT up1989 said:

Can a Train in CM/Auto pass a station starter signal at danger? I know In the seltrac system on the northen line you can't proceed in PM/AUTO until your target advances, does anyone know if its the same for central line?

Undortunately, yes, at several locations

[superteacher]

Aug 25, 2016 10:38:04 GMT drainrat said:

Jul 10, 2016 14:31:12 GMT up1989 said:

Can a Train in CM/Auto pass a station starter signal at danger? I know In the seltrac system on the northen line you can't proceed in PM/AUTO until your target advances, does anyone know if its the same for central line?

Undortunately, yes, at several locations

But surely, a red signal would equate to a target speed of zero?

[Deleted]

Aug 25, 2016 18:24:44 GMT superteacher said:

Aug 25, 2016 10:38:04 GMT drainrat said:

Undortunately, yes, at several locations

But surely, a red signal would equate to a target speed of zero?

Yes indeed, target speed of zero on entering the next block (i.e. stop at the entrance to the block, before entering it, this being marked by the bright red signal). However the maximum safe speed for the block the train is in when standing at the red signal is not zero, so no overspeed has actually occurred until the train has entered the block by passing the red signal. It's more about SPAD mitigation than SPAD prevention. However, reading between the lines, one can only infer that at other locations there's something to prevent this. There were of course comments earlier about the ATP sometimes putting the brakes on if you've been stationary at a red signal for long enough.

Aug 24, 2016 8:52:01 GMT drainrat said:

Jul 10, 2016 19:02:30 GMT trainopd78 said:

The "yellow" aspect is just a dirty signal lens.

You can overrun a signal (SPAD) in coded with the trains emergency brakes coming on as soon as you enter the next section. The ATP puts the brakes on if sitting at a red signal for a certain period (sorry cant remember the exact time - got 60 secs in my head by probably wrong) so the train wont then move until it receives a code to proceed. Theres a bit more to it but thats the basics.

It all depends on the location, some places you can hear the ATP drop out almost immediately, other places it doesn't drop out at all no matter how long you're sat there. train can move at any time!

Presumably, though, that only applies to starting up against one in Coded, surely Auto wouldn't SPAD the starter like that? Of course, in both modes, you could overrun the signal, but that's a separate matter.

[drainrat]

Aug 25, 2016 18:45:52 GMT tut said:

Aug 25, 2016 18:24:44 GMT superteacher said:

But surely, a red signal would equate to a target speed of zero?

Yes indeed, target speed of zero on entering the next block (i.e. stop at the entrance to the block, before entering it, this being marked by the bright red signal). However the maximum safe speed for the block the train is in when standing at the red signal is not zero, so no overspeed has actually occurred until the train has entered the block by passing the red signal. It's more about SPAD mitigation than SPAD prevention. However, reading between the lines, one can only infer that at other locations there's something to prevent this. There were of course comments earlier about the ATP sometimes putting the brakes on if you've been stationary at a red signal for long enough.

Aug 24, 2016 8:52:01 GMT drainrat said:

It all depends on the location, some places you can hear the ATP drop out almost immediately, other places it doesn't drop out at all no matter how long you're sat there. train can move at any time!

Presumably, though, that only applies to starting up against one in Coded, surely Auto wouldn't SPAD the starter like that? Of course, in both modes, you could overrun the signal, but that's a separate matter.

Newbury pk outer rail was (and apparently still is) notorious for trains being able to start up in ATO against a red signal and no codes. When raised through tier 1 and THSC the response was always 'maybe, but the emergency brakes will apply as soon as the train passes the signal'. For whatever reason, there was a reluctance to deal with it, but my guess was that it would be an admittance of failure, after carrying out platform duties it's up to top to check and recheck signal so blame attributed to driver and not a chronic ATO issue. Simple advise is don't start up against a red signal!

Also, several locations namely Woodford, Liverpool st WB home signals and just past track crossover between East Acton white city EB where driver has to be on the ball to knock handle out as stopping at the block markers is 'erratic'

[North End]

Aug 25, 2016 18:24:44 GMT superteacher said:

Aug 25, 2016 10:38:04 GMT drainrat said:

Undortunately, yes, at several locations

But surely, a red signal would equate to a target speed of zero?

Yes, but that applies to the section in advance of the train. The section you're standing on will probably have a proceed code.

I've always been a little unclear as to how it works on the Central Line that the codes drop out after a set time, as it seems to vary across the line. The only safe assumption to make, from a driver's point of view, is that one can potentially always start up against a red signal on the Central, in CM or ATO, therefore one must always make sure to check the starting signal!

On the Seltrac lines the train will not move with no limit of movement authority, so no danger of a SPAD there. The only opportunity to have a SPAD is passing a Stop board in or entering a depot, or passing an RM Hold board in RM without authority. Seltrac is a little erratic in giving the driver the target point in good time, sometimes it comes very early, whilst at other locations it comes late so that if you wait until then before closing the doors you won't get away on zero. Whilst it's bad practice to anticipate the target point advancing, it's become accepted practice to close the doors around 8 seconds countdown regardless of a target point or not. The train won't move without one, and there's always the option to re-open the doors if it doesn't advance. If you don't do this unfortunately the extra seconds can add up to quite a bit of lost time. Can confuse platform staff waiting for the RTD white light though!

[bananaman]

Aug 26, 2016 0:04:24 GMT North End said:

I've always been a little unclear as to how it works on the Central Line that the codes drop out after a set time, as it seems to vary across the line. The only safe assumption to make, from a driver's point of view, is that one can potentially always start up against a red signal on the Central, in CM or ATO, therefore one must always make sure to check the starting signal!

It's only the berth of certain semi-automatic signals that drop the code out after a period of time. It's usually locations where there's points in the overlap, or a reversing move is possible from that position (e.g. a bi-directional platform)

[drainrat]

Aug 26, 2016 6:26:03 GMT bananaman said:

Aug 26, 2016 0:04:24 GMT North End said:

I've always been a little unclear as to how it works on the Central Line that the codes drop out after a set time, as it seems to vary across the line. The only safe assumption to make, from a driver's point of view, is that one can potentially always start up against a red signal on the Central, in CM or ATO, therefore one must always make sure to check the starting signal!

It's only the berth of certain semi-automatic signals that drop the code out after a period of time. It's usually locations where there's points in the overlap, or a reversing move is possible from that position (e.g. a bi-directional platform)

Yep, so sound advice to anyone is check, recheck and check again. The countdown can often give indication as to when signal will clear - around 18 secs left on countdown, but don't anticipate it.

[Tom]

Aug 26, 2016 6:26:03 GMT bananaman said:

Aug 26, 2016 0:04:24 GMT North End said:

I've always been a little unclear as to how it works on the Central Line that the codes drop out after a set time, as it seems to vary across the line. The only safe assumption to make, from a driver's point of view, is that one can potentially always start up against a red signal on the Central, in CM or ATO, therefore one must always make sure to check the starting signal!

It's only the berth of certain semi-automatic signals that drop the code out after a period of time. It's usually locations where there's points in the overlap, or a reversing move is possible from that position (e.g. a bi-directional platform)

The codes generally drop out after 30 or 60 seconds, allowing for some repositioning in the event of a slight misjudgement when stopping, but not too long.
The other thing that happens is that code is re-applied slightly before the signal clears - which can be both a helpful clue and a hindrance!

We did correct ATO data at nine locations about twelve or so years ago to address overruns and SPAD risks in Atuo - every so often a new one crops up though.

[drainrat]

Sept 9, 2016 21:59:03 GMT Tom said:

Aug 26, 2016 6:26:03 GMT bananaman said:

It's only the berth of certain semi-automatic signals that drop the code out after a period of time. It's usually locations where there's points in the overlap, or a reversing move is possible from that position (e.g. a bi-directional platform)

The codes generally drop out after 30 or 60 seconds, allowing for some repositioning in the event of a slight misjudgement when stopping, but not too long.
The other thing that happens is that code is re-applied slightly before the signal clears - which can be both a helpful clue and a hindrance!

We did correct ATO data at nine locations about twelve or so years ago to address overruns and SPAD risks in Atuo - every so often a new one crops up though.

Although WOO WB has never been addressed, and likely never will!....The only location I can think of where you could record a SPAD without passing the signal

[bananaman]

Sept 10, 2016 12:33:23 GMT drainrat said:

Sept 9, 2016 21:59:03 GMT Tom said:

The codes generally drop out after 30 or 60 seconds, allowing for some repositioning in the event of a slight misjudgement when stopping, but not too long.
The other thing that happens is that code is re-applied slightly before the signal clears - which can be both a helpful clue and a hindrance!

We did correct ATO data at nine locations about twelve or so years ago to address overruns and SPAD risks in Atuo - every so often a new one crops up though.

Although WOO WB has never been addressed, and likely never will!....The only location I can think of where you could record a SPAD without passing the signal

That's because the starter is located part-way into the replacing track circuit. When the replacing track is occupied, instead of replacing the signal immediately it is replaced after a three-second delay. Under normal circumstances the delay keeps the signal clear long enough for the train to pass it before going back to danger.

[drainrat]

Sept 10, 2016 15:14:52 GMT bananaman said:

Sept 10, 2016 12:33:23 GMT drainrat said:

Although WOO WB has never been addressed, and likely never will!....The only location I can think of where you could record a SPAD without passing the signal

That's because the starter is located part-way into the replacing track circuit. When the replacing track is occupied, instead of replacing the signal immediately it is replaced after a three-second delay. Under normal circumstances the delay keeps the signal clear long enough for the train to pass it before going back to danger.

Yep, we tried getting it sorted on the signal sighting committee 15yrs ago, was one of first agenda items placed when sighting committees first invited drivers along. Interesting adaptation to have a PAC bend as the 'don't pass' point 😉