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Harlow Town - Restricted Overlaps

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Harlow Town - Restricted Overlaps 04/09/2017 at 08:54 #101521
Andrew G
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552 posts
It seems odd that while the restricted overlap for the Down Passenger Loop provides an operational benefit, in that it doesn't require/lock the loop exit points reverse, the equivalent route for the Up Passenger Loop does require the loop exit points to be reverse which in my view negates the benefit of it.

As this does appear to be correct (see link) I was wondering if anybody can provide some insight into the purpose of the restricted overlaps in the Up direction.

Thanks.

http://photos.signalling.org/picture?/21007/category/2213-2008_may

Last edited: 04/09/2017 at 08:56 by Andrew G
Reason: Added text

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Harlow Town - Restricted Overlaps 04/09/2017 at 19:44 #101532
clive
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2789 posts
I note that 1101 also has a restricted overlap. The only reason I can see for that, and quite possibly therefore for the ROLs at 1110 and 1490, is to allow a train to approach while the ground frame is unlocked.
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The following user said thank you: Andrew G
Harlow Town - Restricted Overlaps 04/09/2017 at 19:45 #101533
clive
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I've just noticed there are two separate releases on that GF. That's curious as well.
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Harlow Town - Restricted Overlaps 05/09/2017 at 00:57 #101537
tallbloke
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10 posts
Andrew G in post 101521 said:
It seems odd that while the restricted overlap for the Down Passenger Loop provides an operational benefit, in that it doesn't require/lock the loop exit points reverse, the equivalent route for the Up Passenger Loop does require the loop exit points to be reverse which in my view negates the benefit of it.

As this does appear to be correct (see link) I was wondering if anybody can provide some insight into the purpose of the restricted overlaps in the Up direction.

Thanks.

http://photos.signalling.org/picture?/21007/category/2213-2008_may
Hi there,

It happened before I started on the railway, but there was a low speed derailment at the catch points at the London end of Platform 1 at Harlow Town, which tipped the train away from the Up Cambridge line. However, due to the location of the catch points, which are very close to rejoining the Up Cambridge line, it was deemed, if it was a "high speed" derailment at the catch points, it could send the train onto the Up Cambridge line and may not activate a track circuit to stop a passing train coming through platform 2.

There is a picture in a West Anglia mess room, I have seen, if I can get a snap of it, I will post it.

On the Down Road, the catch points are a lot further back and away from the Down Cambridge line.

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The following user said thank you: Andrew G
Harlow Town - Restricted Overlaps 05/09/2017 at 19:44 #101551
GeoffM
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6376 posts
Thanks TallBloke.

There is a comment in the data I have for the area that "the reduced overlaps here are virtually useless now!"

SimSig Boss
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