Starting Signals

[Deepgreen]

I readily admit this quite wide ranging-sounding thread is designed for a specific issue, but I hope it also can attract thoughts on other locations.

I use Betchworth station almost every day, in the mornings usually to catch the 0819 to Redhill.

The level crossing is almost always closed shortly before the train arrives, often to allow the passage of the non-stopping Reading train in the other direction a few minutes beforehand, but the starting signal remains at red for over 90% of those occasions (it is occasionally cleared before the arrival of the 0819 but this is rare). The line ahead is devoid of trains until at least Reigate on 99.9% of those occasions.

The train is frequently already a minute or two late arriving, and the approach to the red platform starting signal invariably means a very cautious approach to avoid a possible SPAD. This entails further loss of time.

The only reason I can think of to keep the signal at red on so many occasions is to avoid erroneous non-stopping by an inattentive driver. Given the inevitable loss of time caused by the enforced cautious approach, I believe the risk of erroneous non-stopping is surely far outweighed by the consistent accrual of delay.

Is my assumption correct, and, if so, how have we got to a situation like this?

 

[najaB]

The train is frequently already a minute or two late arriving, and the approach to the red platform starting signal invariably means a very cautious approach to avoid a possible SPAD. This entails further loss of time.

Obviously I'm not a train driver, but I would've thought that if you're booked to stop at a station, the fact that the starter signal is red wouldn't affect how you brake for the station. Could any drivers comment?

 

[edwin_m]

Possibly they want to open the crossing to road traffic after the non-stopping train has passed before lowering the barriers again for the stopper?

 

[jamesst]

Obviously I'm not a train driver, but I would've thought that if you're booked to stop at a station, the fact that the starter signal is red wouldn't affect how you brake for the station. Could any drivers comment?

Yep it affects it very much. At my toc the ruling is 15mph when going over the Aws magnet (approx 200yards from the signal). This does mean that there will be a significant difference in braking techniques for a station with a signal at danger compared to a station where the starting signal has been cleared.

 

[Deepgreen]

Possibly they want to open the crossing to road traffic after the non-stopping train has passed before lowering the barriers again for the stopper?

No, that's not the scenario I am talking about, which is where the crossing remains closed to road traffic after the non-stopping train has passed and the signal remains red until the train has stopped at the platform.

 

[najaB]

Yep it affects it very much. At my toc the ruling is 15mph when going over the Aws magnet (approx 200yards from the signal). This does mean that there will be a significant difference in braking techniques for a station with a signal at danger compared to a station where the starting signal has been cleared.

As a comparison, what speed would you pass typically the AWS magnet if the signal was clear?

 

[Deepgreen]

Yep it affects it very much. At my toc the ruling is 15mph when going over the Aws magnet (approx 200yards from the signal). This does mean that there will be a significant difference in braking techniques for a station with a signal at danger compared to a station where the starting signal has been cleared.

Indeed, and please don't think I am blaming drivers for their crawls into the station here - the SPAD avoidance technique is understandable. My point is that a SPAD would not be possible if the signal were to be cleared (which it occasionally is, meaning that there is no particular rule being enacted at this location).

 

[Tomnick]

There's an AHB roughly half a mile to the east. Does Betchworth station fall within the controls for that AHB? If so, then it'd be normal for stopping/non stopping controls to be provided to allow the sequence (at the AHB) to be suppressed for stopping trains, in which case the platform starting signal would be held at danger to ensure that the train doesn't approach the crossing too quickly (e.g. if "stopping" mode was selected in error for a non-stopping train).

That's no more than an educated guess - I can't confirm it.

 

[MarkyT]

There's an AHB roughly half a mile to the east. Does Betchworth station fall within the controls for that AHB? If so, then it'd be normal for stopping/non stopping controls to be provided to allow the sequence (at the AHB) to be suppressed for stopping trains, in which case the platform starting signal would be held at danger to ensure that the train doesn't approach the crossing too quickly (e.g. if "stopping" mode was selected in error for a non-stopping train).

That's no more than an educated guess - I can't confirm it.

On the face of it I agree with that. Without a station or signal, strike-in treadles for a AHBC would be placed 37 seconds from the crossing at maximum line speed (27s + 10s for minimum road open time in event of another train coming on double track). At (say) 60 MPH (mile a minute) that would be over 1/2 mile so possibly includes the platform, hence a signal and stopping/non stopping controls are required and an additional strike-in between the signal and crossing for trains that have stopped. The signal is there anyway, interlocked for the local crossing, but additional logic would be included in the circuits to delay clearance in the event 'stopping' is selected by the signaller.

 

[Deepgreen]

On the face of it I agree with that. Without a station or signal, strike-in treadles for a AHBC would be placed 37 seconds from the crossing at maximum line speed (27s + 10s for minimum road open time in event of another train coming on double track). At (say) 60 MPH (mile a minute) that would be over 1/2 mile so possibly includes the platform, hence a signal and stopping/non stopping controls are required and an additional strike-in between the signal and crossing for trains that have stopped. The signal is there anyway, interlocked for the local crossing, but additional logic would be included in the circuits to delay clearance in the event 'stopping' is selected by the signaller.

So why the inconsistency? As I mentioned, on some occasions the starter is cleared for the stopping train, but on by far the majority it is not. Surely it should never be cleared if you are correct? BTW, there is no correlation from my observations between the clearance of the starter and whether the non-stopping train in the other direction has passed or has yet to pass.

 

[Tomnick]

So why the inconsistency? As I mentioned, on some occasions the starter is cleared for the stopping train, but on by far the majority it is not. Surely it should never be cleared if you are correct? BTW, there is no correlation from my observations between the clearance of the starter and whether the non-stopping train in the other direction has passed or has yet to pass.

Two possible reasons that I can think of - one is low rail adhesion ('non-stopping' mode routinely selected to mitigate the SPAD risk), the other is human error of some sort (anything from 'non-stopping' mode selected in error). The presence or otherwise of a train on the opposite line won't have any effect on the signalling.

 

[74A]

Its a good question. Does anyone know which signal box controls this signal ?

 

[MarkyT]

So why the inconsistency? As I mentioned, on some occasions the starter is cleared for the stopping train, but on by far the majority it is not. Surely it should never be cleared if you are correct? BTW, there is no correlation from my observations between the clearance of the starter and whether the non-stopping train in the other direction has passed or has yet to pass.

Speculation on my part but 'cleared already' could be the signaller selecting non-stopping for a train that actually stops. You'd get an extended warning time at the AHBC in that event, but probably not by much if a brisk stop at a minor station outside peak, and the whole process would be hurried along anyway with the signal cleared. Likely enough extra warning time to count as overlong in the statistics though. The requirements are pretty stringent. The control feature is there to ensure a high percentage of trains arrive within an upper bound on the warning time. It allows the signaller to delay the start of the warning until at or near the time of departure of a train from the station within the (non-stop) strike in. The specific requirements for the site are stated in the level crossing order. Grossly extended warning time is thought to encourage misuse by road users, but the feature could never be misused to reduce warning time below the minimum. I'd say a signaller is fully justified in using the feature sparingly to hurry along a stopping train where expedient.

 

[pompeyfan]

Could anyone clear up why the starter at Milford on the down is tied into the AHB? I would assume it's to prevent misuse again by trains taking too long to clear the crossing? Non stopping you'd assume it works as a normal AHB, but stopping it works as a time delayed AHB with an added signal?

 

[jamesst]

As a comparison, what speed would you pass typically the AWS magnet if the signal was clear?

It depends very much on the area, the unit itself,the weather and characteristics of the station.

 

[JN114]

Its a good question. Does anyone know which signal box controls this signal ?

Reigate SB

There's an AHB roughly half a mile to the east. Does Betchworth station fall within the controls for that AHB? If so, then it'd be normal for stopping/non stopping controls to be provided to allow the sequence (at the AHB) to be suppressed for stopping trains, in which case the platform starting signal would be held at danger to ensure that the train doesn't approach the crossing too quickly (e.g. if "stopping" mode was selected in error for a non-stopping train).

That's no more than an educated guess - I can't confirm it.

Buckland AHB does have stopping/non-stopping controls on the Down line.

 

[JN114]

Delete, duplicate post.

 

[Phil.]

Its a good question. Does anyone know which signal box controls this signal ?

Reigate.
Here's the signal taken from the crossing.

https://www.google.co.uk/maps/@51.2...NqatxNyRbakdraeyIg!2e0!7i13312!8i6656!6m1!1e1

 

[Deepgreen]

Reigate SB



Buckland AHB does have stopping/non-stopping controls on the Down line.

So, in effect, this means that the two options are:

1. Clear RG84 (Betchworth down starter) before the train arrives at Betchworth station to allow a faster approach than would be expected for a red signal (with its concomitant SPAD risk), but with the penalty of the Buckland AHB being closed for longer for this train to pass.

2. Retain RG84 at red until just before departure (i.e. the much more common occurrence), and allow Buckland AHB to remain open for a couple of minutes longer.

Have I summarised this correctly?

If so, it comes down to the net benefits - saving, say, 30 seconds for the train having a quicker approach and not having to wait for RG84 to clear, with 100 passengers on board = 3000 person seconds, compared with the Buckland AHB being closed for, say an extra 120 seconds. The lane there is very lightly used, but let's say two cars are waiting, each with (generously) four people, so that gives 960 person seconds delay.

This, of course, leaves out the knock-on effects of the train losing further time with option 1 and a number of other low likelihood issues (emergency services stuck at Buckland AHB for example).

 

[MarkyT]

So, in effect, this means that the two options are:

1. Clear RG84 (Betchworth down starter) before the train arrives at Betchworth station to allow a faster approach than would be expected for a red signal (with its concomitant SPAD risk), but with the penalty of the Buckland AHB being closed for longer for this train to pass.

2. Retain RG84 at red until just before departure (i.e. the much more common occurrence), and allow Buckland AHB to remain open for a couple of minutes longer.

Have I summarised this correctly?

If so, it comes down to the net benefits - saving, say, 30 seconds for the train having a quicker approach and not having to wait for RG84 to clear, with 100 passengers on board = 3000 person seconds, compared with the Buckland AHB being closed for, say an extra 120 seconds. The lane there is very lightly used, but let's say two cars are waiting, each with (generously) four people, so that gives 960 person seconds delay.

This, of course, leaves out the knock-on effects of the train losing further time with option 1 and a number of other low likelihood issues (emergency services stuck at Buckland AHB for example).

That about sums it up, but it's not just about delay to road users versus rail users. There is a very stringent requirement that at least 95% of trains should arrive within 75 seconds and 50% within 50 seconds, once the
closing sequence has begun. That can be found in this document:

http://orr.gov.uk/__data/assets/pdf_file/0016/2158/level_crossings_guidance.pdf (p.21).

The reason for this requirement is that excessively long closures can mislead road users into thinking the crossing has failed and attempting to zig-zag around the half barriers. Running times for trains stopping at stations within a AHBC strike in should take into account the red signal usually approached.

 

[Deepgreen]

Thanks for the responses - much appreciated - and thanks MarkyT for the last pointer. I suppose this means that, on the few occasions when a stopping train has the starter cleared well before its arrival at the station, this will mean that its time to pass the Buckland AHB will far exceed the required interval. Is this monitored or recorded anywhere?