Four track for Filton Bank - ongoing discussion

[whole diary]

[DaveHarries]

Dave, some good points there (pun intended), but you can't cater for every possible scenario, as each comes at a cost that in most cases doesn't 'wash its face' in terms of affordibility and ongoing liability.

No I guess not. The other option, perhaps would be to have bi-directional signalling through Platform 2 (the Temple Meads-bound platform) at Lawrence Hill to allow northbound stopping services to use that platform instead of Platform 1 if the need arises. Perhaps someone will think of it at a later date.

Meanwhile a look from the bridge on St. Philips Causeway this afternoon "led" (pun intended) me to notice that Signal BL1818 (ex. signal B131) was switched off: I guess it awaits a feather in relation to the new crossover following reworking of the junction just south of Lawrence Hill.

Dave

[Red Squirrel]

Bit difficult to get a good angle on this, but the attached image shows old and new versions of signal BL1855, on the Severn Beach branch just before Narroways. I was intrigued to see that the new signal seems to have two aspects, whereas the old one just had one - or were my eyes deceiving me?

[martyjon]

Bit difficult to get a good angle on this, but the attached image shows old and new versions of signal BL1855, on the Severn Beach branch just before Narroways. I was intrigued to see that the new signal seems to have two aspects, whereas the old one just had one - or were my eyes deceiving me?

Just perhaps the new signal BL1855 is just perhaps a 4 aspect signal whereas just perhaps the old signal was only a 3 aspect just perhaps. 

[Red Squirrel]

Bit difficult to get a good angle on this, but the attached image shows old and new versions of signal BL1855, on the Severn Beach branch just before Narroways. I was intrigued to see that the new signal seems to have two aspects, whereas the old one just had one - or were my eyes deceiving me?

Just perhaps the new signal BL1855 is just perhaps a 4 aspect signal whereas just perhaps the old signal was only a 3 aspect just perhaps. 

OK, well you keep hold of the potato peeler with both hands and maybe we can make this work.

In the meantime, can anyone with S&T^▸ (Signalling and Telegraph) knowledge explain the significance of the change?

[TonyK]

Was the old one only single aspect? I recall watching it change from red to green just as the driver had mad it out of the cab. Old single aspects couldn't do that. The old one certainly wasn't three aspect.

[stuving]

What it looks like is the new one has two aspects with standard short hoods, while the old one also has two aspects with an extended hood only on the lower (red) one. So maybe that's what it is - it was felt that the red needed screening to improve sighting, but it wasn't felt necessary for the green as it's less safety-critical (and easier to see). LEDs need less help with sighting, so those extended hoods are getting a lot rarer.

That's my guess, anyway - definitely not an expert opinion.

[TonyK]

What it looks like is the new one has two aspects with standard short hoods, while the old one also has two aspects with an extended hood only on the lower (red) one. So maybe that's what it is - it was felt that the red needed screening to improve sighting, but it wasn't felt necessary for the green as it's less safety-critical (and easier to see). LEDs need less help with sighting, so those extended hoods are getting a lot rarer.

That's my guess, anyway - definitely not an expert opinion.

I had looked at RS's picture again as you were typing, and had come to a similar thought about the hooding.

[Red Squirrel]

What it looks like is the new one has two aspects with standard short hoods, while the old one also has two aspects with an extended hood only on the lower (red) one. So maybe that's what it is - it was felt that the red needed screening to improve sighting, but it wasn't felt necessary for the green as it's less safety-critical (and easier to see). LEDs need less help with sighting, so those extended hoods are getting a lot rarer.

That's my guess, anyway - definitely not an expert opinion.

Aha, that makes sense. Thanks.

[SandTEngineer]

'You rang my lord?'

The new signalling on the Filton 4T project is predominately 4-aspect which gives improved headways.  This is a continuation of the signalling at Bristol Parkway which is also predominately 4-aspect.  However it changes to 3-aspect in the Lawrence Hill area to link in with the Bristol Temple Meads area which is predominately 3-aspect.

So as BL1855 signal is now in the 4-aspect area it has changed from a 3-aspect signal to a 4-aspect signal.  The hoods are nothing to do with it.  The older style of LED signal had longer hoods whereas the new 'Lightweight' style have shorter hoods.  The aspects on a 3-aspect LED signal (R/Y/G) are all displayed through the lower aspect and on a 4-aspect LED signal the top aspect displays the additional double yellow aspect only (Y) or what in the trade we call the 'top yellow' or 'second yellow'.

Hope that makes sense?  Read all about it here: http://www.unipartdorman.com/assets/lightweight_signalling_handbook.pdf
Health Warning: Its a large document

[dfm1a]

The new signalling on the Filton 4T project is predominately 4-aspect which gives improved headways.  This is a continuation of the signalling at Bristol Parkway which is also predominately 4-aspect.  However it changes to 3-aspect in the Lawrence Hill area to link in with the Bristol Temple Meads area which is predominately 3-aspect.

Sorry, I don't know their new numbers, but, based on the above, does this 3-aspect rule also apply to the signals in the Down direction formerly known as B152, B252 at Lawrence Hill and B154, B254 at Bristol East which were previously four-aspect? Thanks in advance

[chuffed]

Has the 4 track blockade between Temple Meads and Parkway been extended by a further week ? NRE^‡(resolve) are telling me it will be a bus between those two points up to Sunday 25th November !

[metalrail]

Has the 4 track blockade between Temple Meads and Parkway been extended by a further week ? NRE^‡(resolve) are telling me it will be a bus between those two points up to Sunday 25th November !

Yeah i've been wondering the same.  On the National Rail website current engineering works it now says;

"Buses replace trains between Bristol Temple Meads and Bristol Parkway / Severn Beach from Saturday 27 October until Sunday 25 November"

[Red Squirrel]

The weekends of 24/5 Nov and 1/2 Dec were part of the original blockade. NRE^‡(resolve) timetable still showing weekday trains...

[chuffed]

NRE^‡(resolve) gave me change at Bristol Parkway all day for a train to Sheffield on Mon 19 November......

[TonyK]

NRE^‡(resolve) gave me change at Bristol Parkway all day for a train to Sheffield on Mon 19 November......

Still can, but you'll have to go via Swindon to get there. I think. Maybe not for XC^▸ (Cross Country Trains (franchise)), though, which are going via Swindon to Chelthenham Spa.