class411
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Post by class411 on Jul 1, 2016 11:47:54 GMT
Mentioned HereThis is interesting to me because it definitively answers a question that has been 'open' for some time. Many years ago there was an incident where a passenger's arm was trapped outside the train and suffered minor damage as the train proceeded to the next station. At the time, it was stated on various news media that there was a 'myth' that train doors had to be closed before they could proceed. However, fast forward a few decades and people are once again stating that the doors have to be closed in order for the train to proceed. The interesting part, as far as this subject is concerned, is this: "A spokesman for the RAIB said: "Our investigation identified that the train driver and other railway staff held the same misunderstanding: if someone had a hand trapped in a door it would not be possible for the door interlock light to illuminate and a driver to take power.
This is not the case, and the door was found to be compliant with all applicable standards after the accident."It should be noted that the door system involved was NOT faulty. According to this report, the systems in use do NOT guarantee that there is not a human obstruction before a door is (electronically) considered closed. |
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Post by countryman on Jul 1, 2016 16:05:24 GMT
I saw this today. Yesterday I was at Hayes and Harlington station at ~18.00. There was a lot of police activity with Blues and Twos, and an ambulance arrived as well. When I first saw this, I thought it explained the situation, then I saw the date!
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Post by Deleted on Jul 1, 2016 16:26:30 GMT
Is this also the case for London Underground trains? I've seen passengers caught between closed doors a few times and wondered if it were possible for the train to drag them into the tunnel.
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Post by Chris M on Jul 1, 2016 17:18:31 GMT
Is this also the case for London Underground trains? I've seen passengers caught between closed doors a few times and wondered if it were possible for the train to drag them into the tunnel. Obviously if the driver is aware that someone is trapped they will not start the train and no dragging will occur. If the driver is unaware, then it depends on how they are trapped whether they will be dragged, and if so how far. If there is a large part of them or their belongings caught in the door (e.g. an arm, leg or large bag) then the door interlock will not be obtainable and the train cannot start. In most cases the driver will simply reopen the doors and the person can free themselves without being dragged. On one occasion a few months ago (I think it was the on the Central line) the driver assumed it was someone holding the doors open and didn't release them for about 1-2 minutes while the person trapped and two large men nearby tried to free themselves. I'm not sure whether they passenger freed themselves with or without the driver releasing the doors first. This person was mostly on the train though and so even if power had been obtained they would not have been dragged. If they are trapped by a small object, particularly a thin item of clothing or bag strap, then it is quite possible that the door interlock will not detect anything amiss and allow the driver to take power. In many cases the item can be pulled free of the door and/or released by the person so nobody is dragged. If this does not happen then a dragging may occur, although on stocks like the 09s on the Vic there is a sensitive edge system designed to stop the train automatically if a dragging is detected. In other cases the driver may notice as the train takes power - in the most recent report released by the RAIB relating to the Underground the driver observed unusual movement on the crowded platform as the person was being dragged and stopped the train before they reached the headwall. TfL and LU do do everything practical they can to prevent dragging, but if you do see one happen do your best to alert the driver or other staff. For example if you are on the train, pull the emergency handle - the train should stop quickly if it is still departing a platform. |
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class411
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Post by class411 on Jul 1, 2016 17:42:03 GMT
If there is a large part of them or their belongings caught in the door (e.g. an arm, leg or large bag) then the door interlock will not be obtainable and the train cannot start. Except this does not seem to be the case. In the Great Portland Street incident, in the seventies, it was the victim's upper arm that was in the train - his elbow preventing him from retrieving his arm. In the current incident it was 'just' a hand, but that would imply that the doors were open at least one centimetre. There seems to be a problem with the mechanism that detects when a door is properly closed if it can register closed with a hand between the doors, even is that is within specification as the comments by the RAIB suggest. |
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Post by philthetube on Jul 1, 2016 18:48:45 GMT
A drag incident should never occur with S stock because of the sensitive edge equipment fitted. (also on Victoria line). This immediatley cuts out the motors if the train starts to move with anything trapped in the doors, and seems to be very effective, it had teething problems but now seems to work fine with very few false warnings. I cannot understand why it is not installed on new mainline stock, and I would have thought it would have been an easy retro fit on any train with "plug"doors.
As you say, the GPS incident was in the 70s and I don't think that could happen now with modern stocks.
I will let someone else describe how it works as I would struggle to do that legibly, but if no one comes back I will have a go.
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Post by 100andthirty on Jul 1, 2016 18:51:28 GMT
This is one of the problems with sliding doors with rubber edges. The edges can deform around objects. In addition there is necessarily a tolerance on the setting of the interlocks which prove that the doors are closed. Thus the thickness of a hand is about the same as all the tolerances. That's why LU has the "do not obstruct the doors" (I forget the exact wording) on every door,
This is one of the reasons that the sensitive edges were introduced on the Victoria line and S stock.
That said, there is a lot more to be done. I was amazed to see this statement "Our investigation identified that the train driver and other railway staff held the same misunderstanding: if someone had a hand trapped in a door it would not be possible for the door interlock light to illuminate and a driver to take power." It shows a significant breakdown in communication from engineers to the front line. However, it should be relatively easy to fix - "only" 20000 or so people to reach. It'll be much harder to educate all the passengers (more than 20m of them for LU alone!) not to try and prevent a train leaving by putting a hand between the doors.
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Post by Deleted on Jul 1, 2016 19:39:21 GMT
Putting emergency stop plungers on the high risk lines (i.e. Piccadilly) would be a good idea - it has worked well on the Victoria Line, and all the emergency stop plungers on that line were actually replaced with new improved units a few years ago, when the line was re-signalled.
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Post by Deleted on Jul 1, 2016 20:03:54 GMT
Putting emergency stop plungers on the high risk lines (i.e. Piccadilly) would be a good idea - it has worked well on the Victoria Line, and all the emergency stop plungers on that line were actually replaced with new improved units a few years ago, when the line was re-signalled. We've had this before. How do you imagine this system working? |
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Post by philthetube on Jul 1, 2016 20:48:37 GMT
does anyone know if there has been a serious drag issue with a sensitive edge fitted train?
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class411
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Post by class411 on Jul 3, 2016 10:04:32 GMT
does anyone know if there has been a serious drag issue with a sensitive edge fitted train? If no one has responded in nearly two days, I would guess that the answer to the implied question is no. These incidents tend to get widely reported, and as a few of the people here have some slight interest in railways, I suspect it would have been noticed. However, dragging incidents are extremely rare, so I'm not sure that we can say anything much about the infallibility or otherwise of sensitive edges. My worry with these is that wear and tear and maintenance errors could lead to some door's SE systems not working, and no one would be any the wiser unless there was an accident cause by their malfunctioning. Of course, it may well be that the testing procedures are good enough to ensure that the system continues to provide the protection it was designed to. |
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Post by superteacher on Jul 3, 2016 10:20:30 GMT
Remember that on trains with guards, it wasn't possible for the guard to give the starting signal until the door interlocks were proved closed, which caused the pilot light to come on. However, there was nothing to prevent a driver taking up power.
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Post by John Tuthill on Jul 3, 2016 11:53:28 GMT
Remember that on trains with guards, it wasn't possible for the guard to give the starting signal until the door interlocks were proved closed, which caused the pilot light to come on. However, there was nothing to prevent a driver taking up power. That's true. I can remember donkeys years ago changing at Kennington for a 'Charing +' train, a 38 came around the loop and when it slowed down I could see that the doors on both sides were open. Never found out why. |
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