Bristol Temple Meads - eastern approach remodelling

[Dai Corner]

I’m not joking

Let's hope they overestimated the height, or at least left plenty of slack in the cables!

 

[Yoki]

I’m not joking

I'm positive early OLE feasibility design was used to design the modular construction of the new gantry to ensure compatibility for future electrification. The current construction may not provide full compliance in its current configuration but its designed for OLE to run through there.

 

[Ashley Hill]

Unfortunately that nice new signal gantry may not be fully compatible. Apparently they had to guess, as the OHL design has not been completed yet…

I was under the impression that all new work had to be compliant with electrification standards. The new East gantry certainly looks high enough.

 

[The exile]

I’m guessing the potential problem may be sight lines (as at Ladbroke Grove) rather than physically fitting the OHLE under the gantry.

 

[Annetts key]

As I understand it, the problem is that without a finished OHL design, the ‘drop down’ sections where the signals are located and the staff protection ’cage work’ may need to be altered. The height of the main structure should be okay.

This is not the first time that new signal heads or signal structures have had to be altered or replaced soon after being brought into use, as they no longer meet the required minimum clearance distances. This affected various signals in the Bristol Parkway area when the OHL was installed there.

Often the problem is not that the trains can physically pass. But that the distance between a live pantograph (any part of it) and either the ‘cage’ or a worker on the signal may not meet the minimum distance required in the standard.

 

[edwin_m]

The limits for position of the main contact and catenary are defined relative to the track, and as the location of that is known there will be clearance provided for those. If the concern is the possibility of an insulator blocking the sightline (an issue at Ladbroke Grove I think) then minor adjustments should be possible of the position of the signal or the cage - I'm sure this is a modular design.

What might be more serious is if there is a runoff wire or similar going outside the normal envelope of the OLE above the track. Unless it's a very minor infringement that can also be cured by small movement of the signal, I suggest the answer would then be to tell the OLE engineers to go away and change their design. The signal can't move too far or it will fail sighting or infringe on the next track, and the gantry itself can't be moved as (quite apart from the cost and disruption) the track layout and signalling design will rely on it being where it is. One hopes there has been at least an opinion sought from an OLE engineer that there isn't such an issue at this location.

 

[hwl]

As I understand it, the problem is that without a finished OHL design, the ‘drop down’ sections where the signals are located and the staff protection ’cage work’ may need to be altered. The height of the main structure should be okay.

This is not the first time that new signal heads or signal structures have had to be altered or replaced soon after being brought into use, as they no longer meet the required minimum clearance distances. This affected various signals in the Bristol Parkway area when the OHL was installed there.

Often the problem is not that the trains can physically pass. But that the distance between a live pantograph (any part of it) and either the ‘cage’ or a worker on the signal may not meet the minimum distance required in the standard.

Thinking on electrification and signalling is evolving somewhat (certainly in other regions) with more recent designs LED signal heads that are much small and lighter; and the assumption is that many will need minimal attention till replacement. e.g. signal heads on pivoted arms that can be lifted up to the gantry for work if needed so no need for bulky cages etc. or go for line block and turn the juice off.

edit to add: e.g. these east of Manchester Victoria:

https://www.skyscrapercity.com/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.skyscrapercity.com/attachments/af0fb9cf-b1ab-48fe-9d7e-34f9b15fd159-jpeg.1858027/

 

[edwin_m]

Thinking on electrification and signalling is evolving somewhat (certainly in other regions) with more recent designs LED signal heads that are much small and lighter; and the assumption is that many will need minimal attention till replacement. e.g. signal heads on pivoted arms that can be lifted up to the gantry for work if needed so no need for bulky cages etc. or go for line block and turn the juice off.

edit to add: e.g. these east of Manchester Victoria:

https://www.skyscrapercity.com/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.skyscrapercity.com/attachments/af0fb9cf-b1ab-48fe-9d7e-34f9b15fd159-jpeg.1858027/

Are they using those on the gantry at TM or something more traditional?

 

[nlogax]

That will look lovely with some OLE. One day!

 

[Kingham West]

It looks beautiful, let’s hope the bundlea and other rubbish does not get a foothold, Oxford looked beautiful, now there is rubbish creeping in ..

 

[Sean Emmett]

Wot no buddleja?

Yes it looks good, and drivers already taking advantage of the quicker starts from P3 to the up Filton Relief..

 

[tiptoptaff]

Wot no buddleja?

Yes it looks good, and drivers already taking advantage of the quicker starts from P3 to the up Filton Relief..

Its fun!

Blanket 20 between Dr Days, North Somerset, Lawrence Hill and Bedminster today from 1100-1700 due to heat.

Guessing that's to do with it all being fairly new and the air temp today expected to be mid-high 20s, translating to a track temp in the 40s

 

[Bald Rick]

Guessing that's to do with it all being fairly new and the air temp today expected to be mid-high 20s, translating to a track temp in the 40s

It will be a combination of one or both of a lack of ballast consolidation - which only comes with the passage of traffic - and some outstanding stressing, on a layout that has plenty of curves, with rail temperatures in the 40s.