Interlaced Track

[Ashley Hill]

How were interlaced track sections controlled on mainlines? Was the section controlled by one box and suitably interlocked or could it be mid- section between two boxes. Would it be allowed on today's mainline?

[Fast Line Floyd]

It could be controlled by one box and suitably interlocked or it could be controlled by two boxes and a form of single line protection installed (Token, Train Staff, Acceptance lever/switch etc).

There is no reason why it could not be allowed on todays mainlines with suitable protection.

[Ashley Hill]

Cheers Graham. So theoretically it could be used in a modern signalling centre such as Basingstoke. One of the excuses given for not extending the double track SR mainline from Exmouth Jct to Honiton is the M5 overbridge at Pinhoe,not wide enough for a double line but a generous width for the single. With controls between Basing and Exmouth Jct boxes could interlacing be viable here?

[John Hinson]

Of course, but you would still have a bottleneck.

John

[Andrew Waugh]

I would suspect the main issue with interlaced track these days is the use of concrete sleepers. Clearly interlaced track couldn't use standard concrete sleepers as they would be too short and lack the support for four rails. I doubt it would be economic to design a special concrete sleeper specifically for interlaced track.

You could use wooden sleepers - are these allowed for new work on main lines in the UK?

[davidwoodcock]

I would suspect the main issue with interlaced track these days is the use of concrete sleepers. Clearly interlaced track couldn't use standard concrete sleepers as they would be too short and lack the support for four rails. I doubt it would be economic to design a special concrete sleeper specifically for interlaced track.

You could use wooden sleepers - are these allowed for new work on main lines in the UK?

If interlaced track was used to pass a tight spot, that motorway bridge, for example, paved track could be used.

[Ashley Hill]

Or concrete slab. Yes the bottleneck will still be present but no facing points and only the crossings to maintain.

[Ashley Hill]

So going back to the control of interlaced sections,if on an AB line were double line blocks still used as well as other means? For example Saltash. Although single line between Royal Albert and Saltash boxes double line blocks were still used in conjunction with acceptance levers.

[JRB]

Similar considerations apply on the Hastings line

[Fast Line Floyd]

So going back to the control of interlaced sections,if on an AB line were double line blocks still used as well as other means? For example Saltash. Although single line between Royal Albert and Saltash boxes double line blocks were still used in conjunction with acceptance levers.

Block instruments with acceptance levers is one such method or indeed just acceptance levers or token instruments or tokenless instruments.

[Mike Hodgson]

Interlaced track does not necessarily imply opposite directions - it is possible for parallel fast and slow lines to be interlaced as has happened in the past on ECML.
In this case single line arrangements such as token working are unnecessary and inappropriate, although you would obviously still want form of interlocking to ensure that you could not have trains on both at the same time.

[John Hinson]

Interlaced track does not necessarily imply opposite directions - it is possible for parallel fast and slow lines to be interlaced as has happened in the past on ECML.
In this case single line arrangements such as token working are unnecessary and inappropriate, although you would obviously still want form of interlocking to ensure that you could not have trains on both at the same time.

In such cases, the two lines would share the same block instrument - unless the section was all controlled from one box, such as this:
https://signalbox.org/diagrams.php?id=1085

John

[Richard Pike]

I have seen some very nice pictures of interlaced track at Werrington Junction, near Peterborough. The Midland lines have been interlaced in the shots. Typing in Werrington Junction remodelling as a search is not a lot of use right now though...

[Fast Line Floyd]

Interlaced track does not necessarily imply opposite directions - it is possible for parallel fast and slow lines to be interlaced as has happened in the past on ECML.
In this case single line arrangements such as token working are unnecessary and inappropriate, although you would obviously still want form of interlocking to ensure that you could not have trains on both at the same time.

In such cases, the two lines would share the same block instrument - unless the section was all controlled from one box, such as this:
https://signalbox.org/diagrams.php?id=1085

John

I'm not sure Bollo Lane really counts as interlaced track as at this location it was really just a very long set of points so as to bring the point ends in to the view of the Signalman.

[John Hinson]

It was indeed interlaced track, the reason it was dispensed with had something to do with electrification and the alignment of juice rails . . .

John