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Thread: Drogheda Viaduct

  1. #21
    Senior Member jhb171achill's Avatar
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    I'm unaware of any in Ireland, bar the instances discussed on another board about 5ft 3 track being interwoven (as dual gauge) with 3ft gauge, as at places like Larne Harbour...
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  2. #22
    Quote Originally Posted by DiveController View Post
    Nice shot, Richie!! It looks like this has an interlaced up and down line with check rails on the inside also.

    What would the advantage of an interlaced track (versus merging into a single road) have been? Absence of a facing point at the exit to the bridge in each direction?
    Yes that's exactly the advantage

  3. #23
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    I got out my private helicopter (kindly supplied by Google Maps) and took a flight over Drogheda just now. There are points either end of the viaduct, so it's ordinary single track. I don't know the technical term for the safety rails, they aren't check rails as such which are set just inside the back-to-back gauge. You see them on a lot of bridges though.

  4. #24
    Senior Member tonybonneyba's Avatar
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    Quote Originally Posted by Maitland View Post
    I got out my private helicopter (kindly supplied by Google Maps) and took a flight over Drogheda just now. There are points either end of the viaduct, so it's ordinary single track. I don't know the technical term for the safety rails, they aren't check rails as such which are set just inside the back-to-back gauge. You see them on a lot of bridges though.
    Guide Rails are the technical term
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  5. #25
    Quote Originally Posted by tonybonneyba View Post
    Guide Rails are the technical term
    They are 'Guard Rails'.

  6. #26
    Senior Member DiveController's Avatar
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    Quote Originally Posted by Junctionmad View Post
    Yes that's exactly the advantage


    So I wonder why they needed interlaced track then but in this age of health and safety and high viz vests and ….
    Well, why go with to a facing "Y" point now?
    Are modern points more reliable with regard to absence of potential derailing, someone decided it had been unnecessary in the first place on safety grounds, or what?
    The bridge is no lower now and I presume if the bridge itself was not going to 'hold' a derailing loco then it would not do any better job now. We did have a discussion about facing points and modern stiffer track on another thread here in the last year or so but I'm not sure if any of that factors into this?

    Was the interlaced track controlled by a token/key as there were separate up down lines but these would normally overlap/interlace as here?

    Were the tracks interlaced because bridge was too narrow or could not support the weight of two trains on the bridge simultaneously?
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  7. #27
    Quote Originally Posted by josefstadt View Post
    They are 'Guard Rails'.
    The term guard rails and check rails are interchangeable , with " guard" rail being primarily US rail terminology.

  8. #28
    Quote Originally Posted by DiveController View Post


    So I wonder why they needed interlaced track then but in this age of health and safety and high viz vests and ….
    Well, why go with to a facing "Y" point now?
    Are modern points more reliable with regard to absence of potential derailing, someone decided it had been unnecessary in the first place on safety grounds, or what?
    The bridge is no lower now and I presume if the bridge itself was not going to 'hold' a derailing loco then it would not do any better job now. We did have a discussion about facing points and modern stiffer track on another thread here in the last year or so but I'm not sure if any of that factors into this?

    Was the interlaced track controlled by a token/key as there were separate up down lines but these would normally overlap/interlace as here?

    Were the tracks interlaced because bridge was too narrow or could not support the weight of two trains on the bridge simultaneously?
    Complex track work is an anathema to modern rail companies and especially IE. Modern tamping machines. Etc also dictate the use of simple track work and modern turnouts are pre fabricated virtually like hornby set track.

    The bridge was singled in the 1920s when the centre arch was replaced.

    I presume that the signalling merely treated guantletted track as n a similar way to the current arrangement, with a one train in section approach

  9. #29
    Quote Originally Posted by DiveController View Post
    Were the tracks interlaced because bridge was too narrow or could not support the weight of two trains on the bridge simultaneously?
    The original bridge had had double track, but was worked as a single line to avoid having two trains on the bridge at the same time.

    When the bridge was replaced in the early 1930s, the line was temporarily singled for the duration of the work, and the new bridge was built inside the old one. This then meant that the new bridge was too narrow for double track, but since there had a restriction on having two trains on the bridge at the same time for many years, the provision of gauntleted double track was not a problem. On completion of the new bridge, the old bridge was then dismantled.

  10. #30
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    Are modern points more reliable with regard to absence of potential derailing
    Generally they are - if they are looked after. See "Grayrigg" https://en.wikipedia.org/wiki/Grayrigg_derailment.

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