The Camborne situation I believe is all to do with not blocking the level crossing as the traffic builds up quickly. In normal formation public doors for coaches A/B are usually platformed, TGS/Guards door is not. The door panel to open between A & B is situated by the door in Coach A, so if the train is slightly past the stop-board you'll be unlocking an un-platformed door, and then you'd have to run back to B/C to open.
Of course if the train is in reverse, then the front passenger will definitely be off, and the risk again for the next set of doors still exists.
As readytostart says, door panel locations can change the situation too. Where the emergency doors are in the buffet, there are no door panels, so heading towards London in the normal formation, then it was impossible to open 5 coaches (back in the day of 3 first/5 standard
). Of course a mini-buffet has panels, so you can open 5. Somewhere like Yatton which will easily take 5 coaches could see 4 or 5 being opened purely dependant on the buffet type. A coach the wrong way round in a formation may cause no panels be available between two coaches, so reducing the number available.
There is a
SDO▸ master-guide to tell
TM‡'s how many coaches each platform will fit, and then it's up to their discretion/operating decisions on the day to implement.
As for the
FGW▸ SDO technology, there is also a SDO-HOLD option. "Basic" example. As a TM, if you leave Newbury from the rear door, you are sending a door lock signal down the train. When you arrive at Hungerford and only open the front 6 coaches because of the short platform, when you select doors AHEAD (facing what you are opening), that lock signal from the back of the train is still active, as it is not being cancelled by the doors being opened. As a result, the front doors will open and when the TM removes their key, the doors will lock back-up again as the lock signal from Newbury is still active. However, by selecting HOLD, those forward doors unlocked will stay unlocked and the key can be removed. The TM MUST return to the panel where HOLD was selected to lock the train and dispatch.
However, if when leaving Newbury the TM locks from coach F, the lock signal is then sent from there. So on arrival at Hungerford, they can open the doors ahead from coach F, and remove key and dispatch further down as the lock signal is then cancelled. I would then lock from coach C at Hungerford, as 3 coaches at Bedwyn is next allowing me to open the 3 and move down, but by locking from D/E/F would then require HOLD to be used at Bedwyn. Hopefully that explains a bit of the operating side of it, or just caused more confusion!
Click on the map to explore geographics
