S-Stock 'Doors not in use' flashing

[class411]

Does anyone know why the 'Doors not in use' signs sometimes flash just before doors open or just after they close?

It doesn't happen every time, but it's fairly common.

[Dstock7080]

Jul 16, 2021 8:31:04 GMT class411 said:

Does anyone know why the 'Doors not in use' signs sometimes flash just before doors open or just after they close?

It doesn't happen every time, but it's fairly common.

It depends if the train has accurately stopped exactly on the mark, if it’s just slightly outside tolerance the cab and car light will appear to flash on and off repeatedly.

[philthetube]

Or the train may be on the mark but not picking up the signal from the beacon for some reason, also flashes on when the train is opened up, just until it realises where it is.

[t697]

They also come on for a few seconds during the changeover between Tripcock and ATC Modes at ATC boundary platforms.
Something of a 'feature' rather than a bug that needs fixing.

[spsmiler]

Jul 16, 2021 9:34:26 GMT philthetube said:

Or the train may be on the mark but not picking up the signal from the beacon for some reason, also flashes on when the train is opened up, just until it realises where it is.

hmm... the more the technology, the more there is to go wrong!

[philthetube]

To be fair on that one, overall this bit of technology concerning the doors makes the railway a lot safer and if it does go wrong it can be safely overridden providing procedures are followed.

[firestorm]

The doors system in a quick and simplified way is made up of relays and hard wired controls, once the appropiate beacon signal is gained it allows the correct doors to open. This is different to the system that controls the "doors not in use" panel, which is controlled solely by the train control management system (TCMS), without going into too much depth, it uses something called a Modular input/output or MIO to turn on/off. TCMS is software and there are quite a few components which is connected via the digital output e.g. outer door indicator lights (ODILS), audible alarms in the cab and even the lights for when the door open buttons are pressed in the cab.

When you start involving software, it starts to get rather complicated, however you may have noticed all the systems I have listed above aren't safety critical systems or anything that would stop the train from being moved. Apart from a few train tests that rely on the MIO to operate, it's essentially a nice to have information system.

Jul 17, 2021 9:22:23 GMT spsmiler said:

Jul 16, 2021 9:34:26 GMT philthetube said:

Or the train may be on the mark but not picking up the signal from the beacon for some reason, also flashes on when the train is opened up, just until it realises where it is.

hmm... the more the technology, the more there is to go wrong!

Whilst that is true there is enough redundancy built in, so that key systems will continue to work to not leave a train stranded even if multiple systems fail. 

[bigvern]

This is similar to the old door open buttons on the 95/96TS as these would often be lit at odd times, again had no effect on the door operation, usually a fault with a Train Management Remote Terminal (TMRT)

[class411]

Given that this is not a safety critical system, it doesn't really matter that much, but it's an odd 'feature'*.

The logic for the light would be something like this for each set of doors:

IF

We within x metres of the stopping point for the next station and approaching or stationary

AND

This is a station where this set of doors are inhibited

THEN

Turn on 'door not in use' light.

-------

After turning on light:

IF

Light is on

AND

Train has started after docking

THEN

Turn off light.

----

It's rather hard to see how that logic can produce a flash of the lights when they are not required.



* In software terms, a 'feature' is any bug that you can convince higher management / customers is an intended function.

[t697]

I'm not going to cite the software logic here, but it isn't as proposed above.
Class 411 does have a point though in that as originally specified, the ATC (cancelled Westinghouse version) was due to tell the train in advance of stopping about SDO door cut outs and the indicators would have come on during the station run-in or earlier.
The actually implemented Thales ATC does not do that and it was decided not to modify software to do this based on the CIS database, which cannot account for stations with multiple platforms and varying SDO patterns.

[AndrewPSSP]

Jul 18, 2021 7:07:19 GMT bigvern said:

This is similar to the old door open buttons on the 95/96TS as these would often be lit at odd times, again had no effect on the door operation, usually a fault with a Train Management Remote Terminal (TMRT)

That reminds me.. I know it's slightly off-topic but I do miss the door open buttons on the exterior of the doors on the 1996TS. The light on the button would extinguish maybe ~0.5-1.5s before the doors closing chime and the doors closed.. precious little time that was useful in gauging if I should run or not and allowed me to catch a train that I would otherwise have missed!

Less useful but slightly more aesthetically pleasing also was that they would light before the doors opened (when the door open chime sounded). I miss seeing the occasional person trying to press the button.

[t697]

Jul 18, 2021 17:54:17 GMT AndrewPSSP said:

Jul 18, 2021 7:07:19 GMT bigvern said:

This is similar to the old door open buttons on the 95/96TS as these would often be lit at odd times, again had no effect on the door operation, usually a fault with a Train Management Remote Terminal (TMRT)

That reminds me.. I know it's slightly off-topic but I do miss the door open buttons on the exterior of the doors on the 1996TS. The light on the button would extinguish maybe ~0.5-1.5s before the doors closing chime and the doors closed.. precious little time that was useful in gauging if I should run or not and allowed me to catch a train that I would otherwise have missed!

Less useful but slightly more aesthetically pleasing also was that they would light before the doors opened (when the door open chime sounded). I miss seeing the occasional person trying to press the button.

More than once I've seen people trying to use the blanking panel as some sort of touch control even though it's unlabelled, is not in a contrasting colour and is fairly obviously just a painted panel.