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How Close Are Trains Allowed To Follow?

Discussion in 'Off Topic' started by esteeleiv, Feb 13, 2020.

  1. esteeleiv

    esteeleiv New Member

    Feb 12, 2020
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    Amtrak train is right behind a car carrier, I thought the signals are supposed to prevent trains from getting this close. Is someone controlling the signals or is TSW inaccurate?
  2. Olaf the Snowman

    Olaf the Snowman Well-Known Member

    Oct 6, 2019
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    Oh ok, I see what you mean (4:14:50 in video). I can only speak for the UK so hopefully you’ll find this at least interesting if not helpful.

    In the UK, this is called permissive working. You would not get a main aspect as the section is occupied but rather you would get the position lights- could be ground position lights or position lights associated with main aspect depending on the location. The position lights (2 white lights when clear) means to proceed at caution and be prepared to stop short of any obstruction. The only time permissive working is (normally) used for passenger trains is when you are going in a platform that already has train in it. It tends to be the ‘big’ stations such as Paddington so on the final signal, the signal would stay red and you would get 2 white lights next to it and a platform number. When you approach the other train in the platform, you must stop no closer than 2 metres (6.5 feet). If you want to know the reason, it may confuse you but it is because if the train you are going ‘on top of’ happens to be coupling or uncoupling, they may set back up to 2 feet (0.6 metres) when they are doing the pull test or setting back respectively. So if you stop 6.5 feet from the train in front and that train in front happens to move towards you by 2 feet, there is 4.5 feet safety margin.

    With the situation in the video, that would never be allowed with passenger trains unless there was very exceptional circumstances. It could happen on freight trains or empty passenger trains (ECS) but not out on the mainline- possibly around a depot, goods loops, reception lines, etc....I don’t believe there is a set distance you have to keep back from the train in front so it is down to your judgement but remember, position lights means to proceed at caution and be prepared to stop short of any obstruction whether it be another train or whatever else.* However, the big rule is that when you are following another train, you must not obey any signals that apply to that train; rather, you must wait for the signal to return to danger (e.g. 2 red position lights) and then clear again (2 white lights) for your train.

    *I stress the importance of the definition of position lights because of what could happen if you become complacent- a few months ago, a Class 800 crashed into the back of a HST near Neville Hill depot in Leeds. See picture below

    Position lights associated with main aspect. Position lights is showing ‘clear’ (proceed)

    Ground position light. It is showing ‘danger’ (stop)

    FC910DC3-6CB9-463E-B1F1-8B01CB30223C.png 19C28047-4110-4396-9186-5CA5F379B18C.jpeg
    Pictures of the crash I described above
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  3. Railfan722

    Railfan722 Well-Known Member

    Feb 25, 2018
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    As Olaf described above, this type of movement is known as permissive working. This is very common in the US, and on NS the engineer is required to
    according to the rulebook. Rule 171 territory is unsignalled track that runs under train order operation. At 4:10:48 in the video, we can see that the signal bridge has number plates under the heads, which denotes that it is a non-absolute aspect. Any train can pass this while it is at 'danger' as long as they proceed under 20 mph outside of interlocking limits or 15 mph within interlocking limits, and can stop on sight of any obstruction. Here, the next absolute signal isn't until around 2 miles further up the line on the other side of the Allegheny tunnel in Gallitzin. There, the Pennsylvanian presumably receives the more favorable Medium Clear aspect, increases speed to 30 mph and is switched to the #2 track at CP UN and eventually passes the same autorack train at around 4:33:14.
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