New Semaphore at Oulton Broad North

[grumblingalong]

As has been previously mentioned here Network Rail have recently been working on the Norwich bound platform at Oulton Broad North, bringing the stopping point back away from to crossing to allow the gates to be lowered later, thus relieving severe road congestion in the area.

Part of this work involved replacing the signal. Imagine my surprise to find that rather than a colour light Network Rail have installed what seems to be a new semaphore signal (the old one still stands behind it).

Can anyone shed some light as to why? Have any other semaphores been newly installed that anyone can think of?

 

[AlterEgo]

Banbury had new semaphores installed a few years ago.

http://roscalen.com/signals/Banbury/South.htm#101112

 

[Foggycorner]

It is far easier and cheaper to put up a new semaphore signal that go to all the expence of changing to a new colour light signal.

 

[John Webb]

I understand that it is now considered preferable to have one type of signal in an area rather than mixing semaphores and colour lights (CLS); it apparently is to avoid the circumstances of the brightness of the CLS leading to the missing of a semaphore signal before the CLS. (Although that may not be a problem at this particular location.) The new semaphore is motor-worked, I am told.
(Information from http://forum.signalbox.org/viewtopic.php?f=5&t=7752 for the more technically minded.)

 

[TheEdge]

I believe that Shrewsbury has got plenty of "new" semaphores to keep it relatively constant.

Talking to a signalman a few days changing a signal (as in to colour light from semaphore) is not just a matter of dropping the old one and putting in a new one in, its a remarkably complex move.

 

[grumblingalong]

Well thanks for the info all there was me thinking a colour light would have been easier to put in, the consistency element makes sense too.

 

[MarkyT]

As John implied the big problem for mixing is read-through. A distant signal or an advanced starter well away from other signals would be a better candidate for conversion. As to complications, a colour light needs a compliant approach aspect sequence, with a yellow at braking distance from the red. Where a particular signal is between other stop signals it 's likely all the ones on approach from the distant would also need to be converted.

CORRECTION. It's the aspect sequence FROM the converted signal to the NEXT signal that is important. So if you replace a semaphore with a colour light in the middle of a sequence, circuits must not allow a green aspect to show if the next signal is at danger, and unless there is braking distance between the signals, the colour light must also be approach controlled from red to yellow to slow the train down if the next signal (colour light or semaphore) is at danger.

Distants and advanced starters are the easiest and most popular signals to convert, the 'longest pulls' usually so most difficult to operate manually and more prone to failures. Distants in particular were converted wholesale around much of the network decades ago. They easily satisfy the braking distance and aspect sequence requirements as by definition a distant is braking distance from the first stop signal to which it applies.

 

[snowball]

The Digital Railway trial was going to be on the Wherry Lines, so perhaps it's a digital semaphore?

 

[John Webb]

The Digital Railway trial was going to be on the Wherry Lines, so perhaps it's a digital semaphore?

All semaphore signals are digital - they're either 'On' or 'Off'! Most definitely a 'binary' system.

 

[snowball]

I think a semaphore is more likely to get stuck in an intermediate position than a colour light.

 

[headshot119]

All semaphore signals are digital - they're either 'On' or 'Off'! Most definitely a 'binary' system.

Except when it's wrong

 

[GB]

I understand they had issues commissioning the signal(s) today, large overrun with busses utillised.

 

[DPWH]

All semaphore signals are digital - they're either 'On' or 'Off'! Most definitely a 'binary' system.

Plus semaphores are finger-shaped, and move like fingers, i.e. digitally.

 

[Class172]

I believe that Shrewsbury has got plenty of "new" semaphores to keep it relatively constant.

Talking to a signalman a few days changing a signal (as in to colour light from semaphore) is not just a matter of dropping the old one and putting in a new one in, its a remarkably complex move.

In the past year or so there have also been new installations in Droitwich Spa and Malvern Wells.

 

[Cherry_Picker]

Banbury had new semaphores installed a few years ago.

http://roscalen.com/signals/Banbury/South.htm#101112

They were short lived too, they were removed this summer when Banbury station was completely remodelled.