Traction/Brake Interlock on 320/1/2 Stock

[Crossover]

Just a very quick question around the Class 320/321/322 stock - when the doors are released, do these units have a brake interlock or just a traction interlock? i.e. could a train roll under gravity if the doors are open and the brakes released and could it then go on to take power (/if not, would the driver be able to move the power handle to a power notch but gain no response to the power demand)?

 

[Eng274]

On a gradient with the brakes released, it will roll with the doors open. IIRC the direction controller needs to be in neutral/auxiliary for this to happen. The low speed relay will pick up and apply the brakes at about 3-5mph. I think it is as you say a door/traction interlock so power cannot be taken.

 

[8J]

As I understand it there isn't a brake interlock however there is a traction power interlock. Same as most BR EMU's that are currently in service.

 

[scotraildriver]

They do have a speed sensor fitted (SSF) which applies the brakes around 5mph.

 

[sheepy1991]

Yes in a way, they have a low speed sensing relay (LSSR), you can hear it click in the cab roof over 5mph, once the low speed sensing relay picks up if there is a loss of door interlock then the emergency brakes will apply. It has been known for drivers not to hear the click from the LSSR and open the drivers cab door at 60mph + with the brakes not applying.. They then swifty get taken out of traffic!!
However if the doors are open and the train rolls under the low speed sensing relays threshold (5mph) then no there is no brake or other intervention to close the doors or bring the train to a stand...