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Blue aspect not reverting on TC failure

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Blue aspect not reverting on TC failure 15/07/2019 at 11:21 #119425
grahamj42
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Had a TC failure on a session with blue aspects enabled.

The train list correctly shows T802 stopped at signal 1204, but the blue aspect is still displayed.


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Blue aspect not reverting on TC failure 15/07/2019 at 11:43 #119427
MarkC
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grahamj42 in post 119425 said:
Had a TC failure on a session with blue aspects enabled.

The train list correctly shows T802 stopped at signal 1204, but the blue aspect is still displayed.
It is always advisable to attach a save game to the report

The signal will stay blue as the train standing at it is an ATO train. The blue aspect displays to the signaller to indicate that the train is operating under ATO conditions, as the train has stopped at the signal it is displaying a red aspect to the driver and as such the signal is behaving correctly in this case

It's not my fault! I was left unsupervised.
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Blue aspect not reverting on TC failure 15/07/2019 at 14:10 #119430
clive
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MarkC in post 119427 said:

The signal will stay blue as the train standing at it is an ATO train. The blue aspect displays to the signaller to indicate that the train is operating under ATO conditions, as the train has stopped at the signal it is displaying a red aspect to the driver and as such the signal is behaving correctly in this case
Actually, the signal will be displaying a blue aspect to the driver.

As Mark says, blue aspects mean "operating under ATO conditions". Just because there's a TC failure doesn't mean that ATO is cancelled.

A reversion to red would be an adverse change of aspect in real life, though the sim doesn't treat it as that.

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Blue aspect not reverting on TC failure 15/07/2019 at 20:32 #119438
grahamj42
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Clive,

Thank you for your expert input.

Since posing the question, I found a brief IRSE paper and some photographs on the net.

Am I correct in saying simply :

1. If an ATO-equipped train is detected entering the section, the section signal unconditionally displays the blue aspect.
2. When any train passes the section signal, the signal reverts to red.
3. Occupation of the section ahead by a non-equipped train (or conventional track circuit failure) is handled by ATO as an occupied section, rather than a failure.

Is the blue aspect proved ?
What happens on blue aspect failure ?

Thanks,
Graham

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Blue aspect not reverting on TC failure 16/07/2019 at 04:26 #119442
Edmund1635
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grahamj42 in post 119438 said:
Clive,

Thank you for your expert input.

Since posing the question, I found a brief IRSE paper and some photographs on the net.

Am I correct in saying simply :

1. If an ATO-equipped train is detected entering the section, the section signal unconditionally displays the blue aspect.
2. When any train passes the section signal, the signal reverts to red.
3. Occupation of the section ahead by a non-equipped train (or conventional track circuit failure) is handled by ATO as an occupied section, rather than a failure.

Is the blue aspect proved ?
What happens on blue aspect failure ?

Thanks,
Graham
The important thing to remember here is that ATO equipped trains operate under cab signals, not trackside signals.
The official definition to blue aspect according to the prevailing Safety Rules is, as I quote, "The trainborne Automatic Train Protection equipment is in communication with trackside signalling equipment that cab signalling mode is in use." It also explicitly states that " Blue aspect does not indicate whether the route beyond the signal have been set or not, and whether the train movement is authorised or not."

So to answer your questions:
1. Yes, so long as the trainborne equipment is working correctly.
2. Yes. Any train occupying a TC, whether ATO equipped or not, will put the signal to Danger.
3. Yes. The system will calculate target speed and target distance accordingly and provide this to as cab signal, which the Driver needs to start the train. This is common occurrence in daily operations, especially after a local EMU (ATO equipped) is overtaken by an Intercity Train (runs only on AWS).

Also - as explained above the Blue Aspect by itself is NOT proved. It is only proved if it is supported by a valid Proceed signal, a target speed and target distance in the cab. Any one of these missing and the driver is not allowed by rule to start the train.
Again as above - if a ATO equipped train does not get a Blue Aspect then it's a fault either on the train or trackside equipment. The rule requires the train driver to report to the signalling for further instructions.

Finally - for the scenario you showed, this would be treated by the driver as being held at a Danger signal. If he is not cleared within 1 min, he will contact signaller to obtain instructions. As signaller you will have to first do certain checks (won't detail here since they are not simulated), then authorise the first train to carry out a track check at caution speed. If the failure still won't clear itself, you will have to authorise train to operate on manual mode one by one. In real life, Control Centre may implement handsignalman and/or pilot man working to minimise delays.

Last edited: 16/07/2019 at 04:34 by Edmund1635
Reason: None given

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Blue aspect not reverting on TC failure 18/07/2019 at 16:13 #119485
clive
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Edmund1635 in post 119442 said:
grahamj42 in post 119438 said:

3. Occupation of the section ahead by a non-equipped train (or conventional track circuit failure) is handled by ATO as an occupied section, rather than a failure.

3. Yes. The system will calculate target speed and target distance accordingly and provide this to as cab signal, which the Driver needs to start the train. This is common occurrence in daily operations, especially after a local EMU (ATO equipped) is overtaken by an Intercity Train (runs only on AWS).
More precisely, on open line then the train will be held at the preceding signal because that will be sending an R+0 aspect (equivalent of red conventional signal). The train won't move forward.

The same will apply if the train or TC failure is between a signal and a headway board. But if it's beyond the headway board then the train will get an R+1, allowing it to move up to the headway board. If the platform is fitted with the "follow-on" mode, it will get an R+2 and be able to move even further forward.

Edmund1635 in post 119442 said:
grahamj42 in post 119438 said:

Is the blue aspect proved ?

Also - as explained above the Blue Aspect by itself is NOT proved.
Disagree. It will be fed by the SSI module so the interlocking knows it's failed.

Edmund1635 in post 119442 said:
grahamj42 in post 119438 said:

What happens on blue aspect failure ?

Again as above - if a ATO equipped train does not get a Blue Aspect then it's a fault either on the train or trackside equipment. The rule requires the train driver to report to the signalling for further instructions.
Hmm. My reading of the control tables is that an unlit blue is treated the same as the underlying being unlit. So if we have signals 1, 3, 5, and 7 all showing blue with the line clear up to 7, then the blue light on 3 fails, then I think you should get:
1 = Y/Bk+1
3 = YY+0
5 = Y+0
7 = R+0
From memory, the driver has to call in at 3 but will still be getting the full ATO permissions to proceed to 7.

(Everything here is based on the signalling that was, not the new one being installed.)

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