But Metro trains cannot move without their doors closed.
I know. I was wondering the same thing...
Brothers,
We have muddled two things together.
First, Auto/manual closure of door has more to do with safety and internal Air conditioning.
A huge number of sub urban trains in India (called MEMUs/Local/...) are non air conditioned and therefore closure of door is not required technically. However if the same train starts to move at higher speeds, you will require a door closure system from safety point of view.
Now this system can be used in two ways, Over-ride type or Alert.
A train operator (or driver) will get alarm in his cabin if the doors are closed or not. Now in some technologies, this will give a start permissive to drive the train only when all doors are closed, else driver cannot move. (this is most used technology).
In some cases the system generates and Alert and then Driver has to take action to ensure that doors are closed and then drive away. However, it can overlooked (or jumper).
in case of Delhi Metro (for that matter all Indian Metros), the system is that train cannot move if doors are not closed. Further train comes to stop if door opened accidentally or sabotaged.
General notes
With increase in level of automation, several operator actions are now transferred to PLCs ot micro-processors. These are classified in categories as follows:
GoA stands for Grade of Automation.
I'm not sure what system Bangladesh has selected, hopefully it is amongst best in the world.
Pretty sure it may be the suburban commuter trains. Some of them have "doors" on the newer rakes:
@anant_s can maybe pinpoint what you are talking about better
that is new Bombardier rake.
I'm not sure these have Auto Door Closure by default. Although there are plans to install.
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there is a significant co-operation between India and Bangladesh as far as Railways is concerned. India has supplied High speed LHB coaches recently and i believe these are already in Intercity express service.