Incorrect SDO announcement at Surrey Quays

[talldave]

Does anyone know why Windrush Line services at Surrey Quays announce that you can only alight from the front 4 coaches, when in fact all doors on coach 5 open?

 

[TFN]

Does anyone know why Windrush Line services at Surrey Quays announce that you can only alight from the front 4 coaches, when in fact all doors on coach 5 open?

The northbound platforms allows for 5 coaches but the southbound allows for 4 temporarily while the works take place.

 

[talldave]

The northbound platforms allows for 5 coaches but the southbound allows for 4 temporarily while the works take place.

Thanks! So someone's been a bit enthusiastic in programming SDO for northbound as well as southbound?

 

[Surreytraveller]

Thanks! So someone's been a bit enthusiastic in programming SDO for northbound as well as southbound?

The train assumes it is going into the shortest platform. The train doesn't know which platform it's going into. It might seem counterintuitive to a human, but for all the computer on the train knows, there could be single line working in place (or is it bi-di on the ELL?)
The train has to err on the side of safety and assume its going into the shortest platform

 

[talldave]

The train assumes it is going into the shortest platform. The train doesn't know which platform it's going into. It might seem counterintuitive to a human, but for all the computer on the train knows, there could be single line working in place (or is it bi-di on the ELL?)
The train has to err on the side of safety and assume its going into the shortest platform

I would hope the train knows which platform it's going into, otherwise it doesn't know which side to open the doors (with or without SDO)?

 

[Mojo]

I would hope the train knows which platform it's going into, otherwise it doesn't know which side to open the doors (with or without SDO)?

The driver is responsible for releasing the doors on the London Overground.

 

[Surreytraveller]

I would hope the train knows which platform it's going into, otherwise it doesn't know which side to open the doors (with or without SDO)?

The driver drives the train, not the train. The train doesn't read the signals, the driver does.
Then the driver releases the doors at the station. There may or not be some kind of device which prevents the train opening too many doors at a short platform, but that will be a separate device unrelated to the signalling. Above ground it will be typically GPS, below ground it will be balises. GPS wouldn't be accurate enough for the train to know which platform it is in, so at stations with variable length platforms there will also be balises. If the train does not detect a balise, it will assume it is in the shortest length platform at that station.
PIS systems will typically be set up to tell passengers to be in the front however many coaches to align with the shortest platform, as the PIS is yet another system that cannot read the signals, so doesn't know which platform the train is going to be routed into.

On Thameslink, where there is automatic train control and the train drives itself, the train still wouldn't know which platform it is in until it stops and detects a balise.

 

[Skoodle]

The train detecting which doors to open and the announcement for it are completely separate systems. As I recall, us drivers were given very little notice that it was changing to SDO in the down direction at Surrey Quays. I can imagine that whoever's job it was to update the PIS announcements had late notice too, so probably to cover all bases did both sides, just in case.