Jubilee line door

[John1977]

Hello,

I was on a Jubilee line train this morning. It was busy enough that people were close to the doors due to lack of space.

As we were pulling into a station, a man of average build leant on the door (window) and it opened about a quarter of the way. He promptly let go and it closed again. I was leaning againt those high rests at the end of the carriages so was right next to the door and opening. Had it been even more busy it may well have been a bit dodgy for any passenger that might have been crushed again the door and pretty easy for them to fall out of the train if they were small enough.

However I was curious how this could happen as I thought the breaks engaged if a door opened during travel. The train was I guess breaking as we were pulling into a station, but it was still going quite fast and did not break stronger or quicker than normal. About 6 seconds or so after the door opened/closed the train stopped as normal and the doors opened.

 

[bramling]

Hello,

I was on a Jubilee line train this morning. It was busy enough that people were close to the doors due to lack of space.

As we were pulling into a station, a man of average build leant on the door (window) and it opened about a quarter of the way. He promptly let go and it closed again. I was leaning againt those high rests at the end of the carriages so was right next to the door and opening. Had it been even more busy it may well have been a bit dodgy for any passenger that might have been crushed again the door and pretty easy for them to fall out of the train if they were small enough.

However I was curious how this could happen as I thought the breaks engaged if a door opened during travel. The train was I guess breaking as we were pulling into a station, but it was still going quite fast and did not break stronger or quicker than normal. About 6 seconds or so after the door opened/closed the train stopped as normal and the doors opened.

Simple answer, which is that LU trains are designed on the basis of having mitigations against dragging incidents caused by small items being trapped in the doors. On older trains this is achieved by allowing the doors to be pushed open slightly against a hard spring. Newer trains have the doors locked shut, but there's a detection system called "sensitive edge" instead. So on older trains it's quite normal and acceptable for doors to be seen to come open slightly whilst the train is moving, either if leant against, or occasionally under harsh braking - if this happens then the interlock should be broken which will cut out the motors on the train, but won't apply the brakes unless the driver chooses to.

Mainline trains don't have such mitigation - not yet anyway.

 

[Ken H]

Simple answer, which is that LU trains are designed on the basis of having mitigations against dragging incidents caused by small items being trapped in the doors. On older trains this is achieved by allowing the doors to be pushed open slightly against a hard spring. Newer trains have the doors locked shut, but there's a detection system called "sensitive edge" instead. So on older trains it's quite normal and acceptable for doors to be seen to come open slightly whilst the train is moving, either if leant against, or occasionally under harsh braking - if this happens then the interlock should be broken which will cut out the motors on the train, but won't apply the brakes unless the driver chooses to.

Mainline trains don't have such mitigation - not yet anyway.

surely 1/4 open is enough for a small child to fall out????

 

[bramling]

surely 1/4 open is enough for a small child to fall out????

Maybe. I forget the figure of how far a door is allowed to open, I think it’s only a matter of a few inches, but definitely enough to produce a noticeable opening (which in the heat of the instant people can form the impression is a bit more than it actually is).

Personally I think it’s a worthwhile trade-off - from a user’s point of view I’d value the ability to extricate myself from potentially being dragged.

Operationally there’s a negative from the arrangement as it can mean trains are prone to losing pilot light, especially if people are leaning against doors or there’s a weak interlock somewhere on the train (it only takes one!). This can be a proverbial pain as it means a crush-loaded train can be prone to losing time if it keeps losing pilot light.

 

[Dstock7080]

Maybe. I forget the figure of how far a door is allowed to open, I think it’s only a matter of a few inches, but definitely enough to produce a noticeable opening (which in the heat of the instant people can form the impression is a bit more than it actually is).

On older trains which have the push-back facility, 100mm (4”).

1995/1996 Stock double-door opening: 1406mm; single-door opening: 703mm

 

[John1977]

Thank you that makes sense. I was just confused as for example, in the past a train has not been able to depart if there is a rag stuck in a door which can only be a few mm's.

Would the door closed light go off in the scenario of the door being leaned on, does the driver just carry on as normal if this occurs?

Thank you.

 

[bramling]

Thank you that makes sense. I was just confused as for example, in the past a train has not been able to depart if there is a rag stuck in a door which can only be a few mm's.

Depends on the circumstances. The doors have a rubber seal on the edge, which compensates for the fact that the interlocks can't be 100% sensitive otherwise the trains would be forever losing interlock. It is this rubber area which introduces the problem of objects being caught without being detected. The "sensitive edge" is an additional feature on newer trains which addressed this.

Would the door closed light go off in the scenario of the door being leaned on, does the driver just carry on as normal if this occurs?

Yes, once the door has opened enough that the interlock is broken. How the driver responds will depend upon circumstances. Normally if it's departing a station platform then he is likely to stop the train, although if the interlock is missing only for a second and there's a decent monitor view of the platform then likely not. If it's whilst the train is running then again providing the interlock comes back then he will continue. In all cases if the pilot light stays extinguished then there's procedures to follow - in that situation the train won't be able to motor so some form of remedy will be necessary. Often a suitable public address announcement assists the situation - especially if the driver manages to gently advise that if the problem keeps occurring then the train will have to be withdrawn from service!