Permanent 10 mph through Bristol TM platforms

[D1009]

I went through Bristol TM earlier today, the first day of operation after the Easter blockade, and noticed that the St Andrews Crosses have been replaced with back to back signals. What to me is less welcome is that a 10 mph Permanent Speed Restriction has been imposed through at least platforms 3 to 12 inclusive. Whilst this may not cause actual delay to trains with the amount of recovery etc time in the schedules, I'm sure it will lengthen the time it will take to recover from disruption.

 

[MarkyT]

I went through Bristol TM earlier today, the first day of operation after the Easter blockade, and noticed that the St Andrews Crosses have been replaced with back to back signals. What to me is less welcome is that a 10 mph Permanent Speed Restriction has been imposed through at least platforms 3 to 12 inclusive. Whilst this may not cause actual delay to trains with the amount of recovery etc time in the schedules, I'm sure it will lengthen the time it will take to recover from disruption.

I believe this is just the first stage in a major track renewal and remodelling project. Carrying out the sequential layout changes as data changes within a new processor based signalling system will be a lot more straightforward and cheaper than attempting to reconfigure the old relay based equipment multiple times. The same approach, of first resignalling the old layout, was taken with some other recent major remodelling schemes such as Reading and London Bridge. I suspect the final layout will raise speeds, and it could be that the 10mph has been chosen to help protect staff working on the track and signalling in the vicinity through the following stages. Clearly the opportunity to make some of the final changes has already been taken, such as provision of the mid-platform signals in place of the St Andrews cross boards.

 

[Senex]

Can any of the signalling specialists explain this really severe reduction? The same thing happened at Leeds after that had been extensively changed , so that now most of the platforms there are 25 to depart but 10 over 15 for arrivals, which is horribly restrictive and time-wasting. I don't know of anything similar at the large continental stations I know that have been resignalled in recent years.

 

[Darbs]

It's to reduce risk with the new platform sharing signals, in agreement with all involved Parties, it's not causing a problem!

 

[edwin_m]

It's to reduce risk with the new platform sharing signals, in agreement with all involved Parties, it's not causing a problem!

10mph versus 25mph for any more than a few metres is likely to have some impact. Even if the boards are on the entry to the platforms travelling 200m at 10mph loses about 20s. Couldn't something have been done with delayed yellows approaching the platforms if a suitable overlap beyond the mid-platform signal wasn't available?

 

[Darbs]

I'm not privy to all the ins and outs of it all but I worked it this morning and it was OK! Just getting ready for a 12 hour night on it from 7!

 

[D1009]

It's to reduce risk with the new platform sharing signals, in agreement with all involved Parties, it's not causing a problem!

May I respectfully suggest that it's a little early to say it's not causing a problem before the first day of operation is over?

 

[snowball]

Network Rail's biggest ever signalling upgrade according to this press release:

https://www.networkrail.co.uk/feeds/biggest-ever-signalling-upgrade-delivered-in-bristol/

Network Rail delivered their biggest ever signalling upgrade today (4 April) with the £130m work enabling GWR to deliver more frequent services to London, quicker journeys and more seats per train from 2019.

The signalling upgrade in Bristol took place over Easter weekend and involved more than 500 members of Team Orange working round the clock to remove old 1970’s analogue signalling and install and test new digital signalling equipment. It means most of the signals in Bristol will be controlled from a state of the art signalling centre in Didcot rather than the 1970s signalling room behind Bristol Temple Meads station.

This is the third of a four stage £250m project to entirely resignal Bristol Temple Meads and the surrounding area. The final phase of the project will take place at Easter 2019. The project, which forms part of Network Rail’s Railway Upgrade Plan, combined with doubling the number of tracks between Bristol Parkway and Bristol Temple Meads later this year, will transform travel into Bristol, enabling GWR to continue introducing new trains as part of their biggest fleet upgrade for a generation.

Mark Langman, route Managing Director for Network Rail’s Western Route, said:

“It is a great achievement to have delivered our biggest ever signalling upgrade in just five days enabling GWR to deliver more services, quicker journeys and more seats in Bristol from next year and more reliable services for Crosscountry to Birmingham and the north

“We had more than 500 members of Team Orange working over Easter to deliver the £130m upgrade, which together with the doubling of the tracks between Bristol Parkway and Bristol Temple Meads later this year will transform rail travel in the city.

“We thank passengers for their patience throughout the upgrade and ask them to bear with us as there may be a bedding in period as we move from the dated signalling system to a state of the art modern system, with new ways of working at Bristol Temple Meads.” “I would also like to pay tribute and thanks to colleagues in the Train Operators who have worked tirelessly over the past few days to enable the first day of operation to be a success”

Mark Hopwood, Managing Director for GWR, said:

“After much hard work over the longer weekend to keep people moving, and to ensure a smooth transition to new signalling systems this morning, I am pleased Network Rail has been able to complete this work.

The new signalling systems, once bedded in should provide us with more reliable infrastructure, and with the continued delivery of new Intercity Express Trains will enable GWR to offer seven trains an hour between Bristol and London Paddington, quicker journeys and more seats per train”.

 

[The Planner]

Biggest ever? Maybe on the Western but I would be surprised if nothing has been larger than this in the past elsewhere.

 

[Bald Rick]

I believe this is just the first stage in a major track renewal and remodelling project. Carrying out the sequential layout changes as data changes within a new processor based signalling system will be a lot more straightforward and cheaper than attempting to reconfigure the old relay based equipment multiple times. The same approach, of first resignalling the old layout, was taken with some other recent major remodelling schemes such as Reading and London Bridge. I suspect the final layout will raise speeds, and it could be that the 10mph has been chosen to help protect staff working on the track and signalling in the vicinity through the following stages. Clearly the opportunity to make some of the final changes has already been taken, such as provision of the mid-platform signals in place of the St Andrews cross boards.

Minor point, but London Bridge was not resignalled on the old layout prior to works; most stageworks were done on the old system (Westpac Mk1), with the resignalling done in sequence when the final layout was achieved for individual stages. This was done to keep data changes in the interlockings at least 4 months apart for version control.

 

[Bald Rick]

Biggest ever? Maybe on the Western but I would be surprised if nothing has been larger than this in the past elsewhere.

I didn’t see the resource plan, but it was a big commissioning in a short space of time, so wouldn’t be surprised.

Having said that, the Waterloo upgrade was billed as the biggest every change to a relay interlocking, which rather missed the work going on a mile to the east.

 

[Railsigns]

NR describing the old signalling as 'analogue' seems a tad misleading. A relay isn't an analogue device.

 

[adrock1976]

I would like something clarified in the press release that refers to 7 trains per hour between Bristol and London Paddington.

Mark Hopwood, Managing Director for GWR, said:

“After much hard work over the longer weekend to keep people moving, and to ensure a smooth transition to new signalling systems this morning, I am pleased Network Rail has been able to complete this work.

The new signalling systems, once bedded in should provide us with more reliable infrastructure, and with the continued delivery of new Intercity Express Trains will enable GWR to offer seven trains an hour between Bristol and London Paddington, quicker journeys and more seats per train”.

I am aware of 4 trains per hour between Temple Meads and Paddington, with 2 being via Chippenham and the other 2 being via Filton and Parkway.

What are the other 3 trains that would make it up to the 7?

 

[Dai Corner]

I would like something clarified in the press release that refers to 7 trains per hour between Bristol and London Paddington.



I am aware of 4 trains per hour between Temple Meads and Paddington, with 2 being via Chippenham and the other 2 being via Filton and Parkway.

What are the other 3 trains that would make it up to the 7?

The ones from South Wales, calling at Parkway

 

[Signal Head]

I believe this is just the first stage in a major track renewal and remodelling project. Carrying out the sequential layout changes as data changes within a new processor based signalling system will be a lot more straightforward and cheaper than attempting to reconfigure the old relay based equipment multiple times. The same approach, of first resignalling the old layout, was taken with some other recent major remodelling schemes such as Reading and London Bridge. I suspect the final layout will raise speeds, and it could be that the 10mph has been chosen to help protect staff working on the track and signalling in the vicinity through the following stages. Clearly the opportunity to make some of the final changes has already been taken, such as provision of the mid-platform signals in place of the St Andrews cross boards.

Actually London Bridge was largely done on the (geographical) relay interlockings, as it wasn't thought possible to get the equipment approvals and data ready in time, although that had been the original intention. All but the last stage of the Low Level (Central) side was done in this way.

The High Level (Eastern) side was tackled in the same way, though it was considerably simpler, as it mainly consisted of progressively taking parts of the layout out of use, and plain lining connections, leaving just enough in to run the service.

 

[MarkyT]

Minor point, but London Bridge was not resignalled on the old layout prior to works; most stageworks were done on the old system (Westpac Mk1), with the resignalling done in sequence when the final layout was achieved for individual stages. This was done to keep data changes in the interlockings at least 4 months apart for version control.

Actually London Bridge was largely done on the (geographical) relay interlockings, as it wasn't thought possible to get the equipment approvals and data ready in time, although that had been the original intention. All but the last stage of the Low Level (Central) side was done in this way.

The High Level (Eastern) side was tackled in the same way, though it was considerably simpler, as it mainly consisted of progressively taking parts of the layout out of use, and plain lining connections, leaving just enough in to run the service.

Thanks for the clarifications. At least with geographical relay sets successive reconfigurations are a little easier than with a free-wired system as at Bristol and Reading.

 

[Dai Corner]

Could someone explain to this layman what a geographical relay set or free-wired system is please?

 

[Signal Head]

Thanks for the clarifications. At least with geographical relay sets successive reconfigurations are a little easier than with a free-wired system as at Bristol and Reading.

Especially when it's E10K!

I'll get me coat

 

[MarkyT]

Could someone explain to this layman what a geographical relay set or free-wired system is please?

Geographical interlocking uses standard pre-wired, factory-tested blocks of relay logic for each signal and point that are connected together by cables in the same architecture as the track layout itself using multicore cables with plug couplers. Although relatively quick to design and test, this technology can be comparatively expensive as each geographical relay set has to cater for the most complex case of signal or point functionality, whereas many examples of each in a typical layout don't have such complexities. Geographical interlockings can also be comparatively large for the same reasons. Free wired interlockings also use standard circuits, but they are individually customised in the design for the particular track and signalling layout required. They only include the precise functionality actually required for the particular application so can save considerably on the number of relays and space required especially for smaller and simpler layouts. Every single wire is individually run and terminated so there's comparatively more work in building and testing. With geograpical it can be easier to reconfigure the layout than with free-wired.

 

[Signal Head]

Could someone explain to this layman what a geographical relay set or free-wired system is please?

Free-wired (there are various different types, some based on major signalling contractor's original designs) - every circuit is designed from scratch, but following standard conventions, and every wire is run in on site between individual relays.

Geographical (again, there have been several varieties, two main ones are Westpac (manufactured by Westinghouse) and GEC geographical (originally designed by Siemens, then known as SGE) - these systems use prepackaged units or 'sets' of relays, factory-wired to provide interlocking facilities for specific features of the layout signals, points, track circuits etc. These are then connected together in a manner which matches the geographical layout on the ground (hence the name)

 

[MarkyT]

Especially when it's E10K!

I'll get me coat

Actually, for the same layout, a remote E10K standard Western Region free-wired interlocking would contain many fewer individual safety relays and wires than one designed to BR 'Yellow book' standard circuits! WR installations make up for that with more complex panel circuits, although these typically use cheaper non safety 'post office' relays.

 

[Signal Head]

Actually, for the same layout, a remote E10K standard Western Region free-wired interlocking would contain many fewer individual safety relays and wires than one designed to BR 'Yellow book' standard circuits! WR installations make up for that with more complex panel circuits, although these typically use cheaper non safety 'post office' relays.

Agreed - but all those soldered PO relay set connections, nightmare!

 

[MarkyT]

Agreed - but all those soldered PO relay set connections, nightmare!

I hate soldering too. Give me a nice crimped spade or ring terminal any day!

 

[Dai Corner]

Free-wired (there are various different types, some based on major signalling contractor's original designs) - every circuit is designed from scratch, but following standard conventions, and every wire is run in on site between individual relays.

Geographical (again, there have been several varieties, two main ones are Westpac (manufactured by Westinghouse) and GEG geographical (originally designed by Siemens, then known as SGE) - these systems use prepackaged units or 'sets' of relays, factory-wired to provide interlocking facilities for specific features of the layout signals, points, track circuits etc. These are then connected together in a manner which matches the geographical layout on the ground (hence the name)

Thank you, and @MarkyT

 

[kaiser62]

So based on the above (which makes sense) can you mix the free-wired and geographical approaches, or is it 'all one or all the other'?

In a large project I could see how a bit of both would be useful.

 

[edwin_m]

I suspect mixing free-wired and geographical on the same bit of track would give most of the disadvantages of both and not many of the advantages. It is in any case academic, because any new interlocking these days would be processor rather than relay based.

 

[swt_passenger]

Is it fair to say that the so-called ‘modular signalling’ has its roots in geographic interlocking?
Modular was touted as a means of combining standard functionality wasn’t it, IIRC.

 

[MarkyT]

So based on the above (which makes sense) can you mix the free-wired and geographical approaches, or is it 'all one or all the other'?

In a large project I could see how a bit of both would be useful.

I suspect mixing free-wired and geographical on the same bit of track would give most of the disadvantages of both and not many of the advantages. It is in any case academic, because any new interlocking these days would be processor rather than relay based.

Some panels do or did control a mixture of remote interlockings of different types. Mostly this occurred when some older but still serviceable smaller free wired interlockings were consolidated from local signal box control to a larger more centralised panel. Victoria Signalling Centre has or had some of these, while new interlockings provided at the larger stations and junction sites were all GEC Geographical. Workstation based systems as employed in ROCs take this even further, being compatible with a wide range of old and new interlocking technologies.

 

[MarkyT]

Is it fair to say that the so-called ‘modular signalling’ has its roots in geographic interlocking?
Modular was touted as a means of combining standard functionality wasn’t it, IIRC.

Yes I think that was in people's minds. It was very much about standardising the trackside equipment as well, from which we get the pared down minimalist nature of some of the the latest conventional schemes, with lightweight, near zero maintenance 'searchlight' LED signals and long block sections usually requiring almost no intermediate equipment due to highly scaleable axle counters, and the lower overall power requirement of the equipment making a more distributed power and backup architecture more practical. The one thing that stands out (literally) today is the disproportionate bulk of some modern signal structures, reaching out above future wires that may never come, when the simple folding straight post integrated signal is not suitable.

 

[D1009]

I suspect the final layout will raise speeds, and it could be that the 10mph has been chosen to help protect staff working on the track and signalling in the vicinity through the following stages. Clearly the opportunity to make some of the final changes has already been taken, such as provision of the mid-platform signals in place of the St Andrews cross boards.

I suspect the 10 mph will be permanent, as from talking to industry insiders the St Andrews Crosses were considered an anachronism which was viewed has a high collision risk, even though I can't remember an accident which was attributed to them. The only means of getting the station to meet current standards while still handling the current level of traffic was to adopt the intermediate back to back signals and a 10 mph restriction, with no AWS within the station limits. I can envisage more missed connections in the future, especially if from platform 15 to platform 1, as sometimes happens.