Signals now on the central line.

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.

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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.)

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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?

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.

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?

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.

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

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!

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

Undortunately, yes, at several locations

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.



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.

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!

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.