Leaning on the doors

[island]

Sometimes when I’m travelling (usually on the Central line), the train jerks and stops very shortly after leaving a station, before getting going again. On occasions the driver announces that this is because people are leaning on the doors and would they stop.

What exactly is happening here?

 

[Mike395]

The door interlock sensors are particularly sensitive as I understand it, so the slightest pressure on the doors during acceleration can break interlock and apply the emergency brake. It sometimes happens on the Piccadilly line too, though nowhere near as often.

 

[Nick66]

If anyone touches a door with any part of the train in a station it will automatically stop.

 

[rebmcr]

From another thread:

Not exactly on the topic of things making the tube feel faster but today I noticed something whilst visiting London today: The northern line (both branches) pulled off from each station with quite a jolt, enough to nearly knock my wife onto the adjacent person's lap on two occasions!

Is this something new to aid running times? I would have only associated such abrupt pull-offs with pre-1995 stock. That said, I might just not be used tubes anymore or / and have been spoiled by the S stock we came in on, so take me with a pinch of salt

That's when someone braces themselves against the doors (not leaning outwards, but forward against the acceleration), which pushes them open enough to lose interlock and cut traction power. The force they were putting on the doors promptly stops, and the motors resume powering. It can loop a few times!

 

[rebmcr]

If anyone touches a door with any part of the train in a station it will automatically stop.

That's broad enough to be untrue. Tens of thousands of passengers do so (touch the doors) during every peak without triggering any safety mechanisms.

It sometimes happens on the Piccadilly line too, though nowhere near as often.

It's very common during busy periods on the Jubilee.

 

[Dstock7080]

The door interlock sensors are particularly sensitive as I understand it, so the slightest pressure on the doors during acceleration can break interlock and apply the emergency brake.

Losing the door interlock will not apply the emergency brake automatically, driver intervention will.

 

[Mike395]

Losing the door interlock will not apply the emergency brake automatically, driver intervention will.

Ah interesting, so loss of interlock just stops acceleration rather than actively applying the brakes?

 

[spinba11]

What’s happens on the the S/09 stock when the sensitive edge is tripped? Do they lose traction like the other stocks.

 

[Dstock7080]

Ah interesting, so loss of interlock just stops acceleration rather than actively applying the brakes?

What’s happens on the the S/09 stock when the sensitive edge is tripped? Do they lose traction like the other stocks.

Correct.
2009 Stock and S Stock have the additional sensitive-edge system, only armed when the doors are proved closed, within station limits; this will activate the emergency brake within station limits if an item is pulled against the sensitive edge. Before the doors are proved closed these Stock have obstacle-detection, which will automatically re-open the affected door 3-times until the item is removed or stall open if it isn't.

 

[spinba11]

I’ve heard that they will only activate if the pulling is from the outside of the train, is that correct?

 

[Dstock7080]

I’ve heard that they will only activate if the pulling is from the outside of the train, is that correct?

Not correct, it will detect pulling in any direction, if with or against the direction of travel too.

 

[philthetube]

Now it has bedded in the sensitive edge isw a fantastic system which seems to work really well, I am surprised it is not mandatory for all new rail stocks.

 

[bionic]

On LU stock loss of interlock only breaks the forward wire which is why the motors drop out and the train jerks. The driver will restroke the handle and 99% of the time interlock will come back and they can take power again. If it doesn't come back then they'll need to stop and investigate. On older LU stocks such as the 72s the door interlocks are mercury switches.

On mainline stock loss of interlock will interupt the brake continuity circuit and apply the emergency brake immediately. On most stocks this is speed sensed so it doesn't apply the brake if the train is already stationary and a release has been put up.

Sensitive edge on modern LU stock is different to the traction/door interlock and only active after interlock is proven and within station limits if the sensitive edge feels resistance, eg: if there's a strap caught in the door from the inside and the owner doesn't pull on it nothing will happen. But if it's outside and the person is getting dragged (or they pull on it from the inside - within station limits) it will put the emergency brake on.

 

[axlrosen]

I once heard a driver announce annoyedly that we should not yank things out of the door. He said that if something gets stuck in the doors, please leave it there until the doors open to the next station. But that seems awfully dangerous to me.

Last month someone had their hood caught in the door, and I yanked it out. Was that the right thing to do?