Signalling problems on the Portsmouth Direct Line

[Annetts key]

There comes a point with alterations to a relay interlocking where you start to think “Wouldn’t we be better just renewing it with something more modern?”.

Yep.

There are also other factors such as material availability/support, does the design expertise still exist, space availability. Each case needs to be looked at on its own merits.

Yes, but to be fair, that applies to many types of equipment.

 

[DelW]

Anyway, whatever Wessex Route's aspirations for Eastleigh and Salisbury may be, they might struggle to meet any demand in the Portsmouth area if they don't get on with doing Havant.

Is that likely to be a problem for the foreseeable future though? I don't know about other routes, but the Direct is only running 2tph to Portsmouth, i.e. only 2/3 of the service level of the last 20+ years. AIUI the 2017 intention to increase to 4tph throughout (by extending the Haslemere terminators) is now dead and buried, and even a return to 3tph seems unlikely.

 

[Nicholas Lewis]

The whole of Havant box needs ripping out and starting again, various signals with temporary approach control on because particular signal heads can’t display a green without the whole system going pop and going into a “hard” fail safe. Regular code 2 AWS issues (Horn vice bell), there’s been repeat failures at Bedhampton (although this wasn’t actually the fault of the signalling or its design), and Portcreek Jn. Various off indicators and banner repeaters also regularly bagged up because they’ve failed, which in some cases causes multiple signals to revert to red.

Its great how the public have to put up with months of disruption back in 2008 because the industry was going to deliver more reliable journeys but have ended up with something worse. Its just as well the mechanical signalling at the likes of Littlehampton and Bognor just keep going despite being over 100 years old in the case of Littlehampton.

 

[Annetts key]

Its great how the public have to put up with months of disruption back in 2008 because the industry was going to deliver more reliable journeys but have ended up with something worse. Its just as well the mechanical signalling at the likes of Littlehampton and Bognor just keep going despite being over 100 years old in the case of Littlehampton.

I remember the time when the two most important requirements for signalling equipment were safety and reliability (both determined by really good design and years of practical testing followed by design improvements until "the" "experts" were happy).

 

[DelW]

Another full closure of the line has now been announced on posters on stations, this one being Monday 24/7 to Friday 28/7 inclusive. It's confirmed on this page*, which also gives some information on what works took place under previous closures.

A lot of new concrete ducts have been laid along station platforms in the last few weeks.

*Edit: the link I intended hasn't worked, the NR web page is

Portsmouth Direct Upgrade - Network Rail

The Portsmouth Direct Upgrade sees us upgrading signalling and track from Woking to Portsmouth Harbour to improve services.

www.networkrail.co.uk

 

[zwk500]

Another full closure of the line has now been announced on posters on stations, this one being Monday 24/7 to Friday 28/7 inclusive. It's confirmed on this page*, which also gives some information on what works took place under previous closures.

A lot of new concrete ducts have been laid along station platforms in the last few weeks.

*Edit: the link I intended hasn't worked, the NR web page is

Portsmouth Direct Upgrade - Network Rail

The Portsmouth Direct Upgrade sees us upgrading signalling and track from Woking to Portsmouth Harbour to improve services.

www.networkrail.co.uk

Do we know when the transfer to Basingstoke ROC is actually due to take place?

 

[infobleep]

Is that likely to be a problem for the foreseeable future though? I don't know about other routes, but the Direct is only running 2tph to Portsmouth, i.e. only 2/3 of the service level of the last 20+ years. AIUI the 2017 intention to increase to 4tph throughout (by extending the Haslemere terminators) is now dead and buried, and even a return to 3tph seems unlikely.

The Network Rail web page on the works says this:

With the new signalling system installed, the line will be more reliable and we will be able to increase the future potential capacity of the line for train services.

Portsmouth Direct Upgrade - Network Rail

The Portsmouth Direct Upgrade sees us upgrading signalling and track from Woking to Portsmouth Harbour to improve services.

www.networkrail.co.uk

They do say potential capacity rather than capacity.

 

[zwk500]

The Network Rail web page on the works says this:

Portsmouth Direct Upgrade - Network Rail

The Portsmouth Direct Upgrade sees us upgrading signalling and track from Woking to Portsmouth Harbour to improve services.

www.networkrail.co.uk

They do say potential capacity rather than capacity.

IIRC the work was required to accommodate the 20-year aspirations at time of design (late 2019/early 2020).

 

[MarkyT]

I'm not a signalling engineer so I don't know the ins and outs but when I was looking at some projects around Southampton a signalling engineer was very concerned about the capacity of the interlocking to take on much more function.

I don't know the current situation, but Southampton's early 1980s station area relay interlocking, and some others in the vicinity of the same vintage, were showing signs of wire insulation degradation around two decades ago and had restrictions imposed on what work was allowed to be carried out within them. In most such cases, the installations are deemed tolerably safe, subject to further regular inspections and as long as the wiring isn't disturbed, by major alterations for example. There was a scheme in mind to replace the interlocking with 'interfaced SSI', where the interlocking logic is handled in the normal way by the processor-based cubicles, but the trackside functional modules are housed in the old relay room rather than being distributed in lineside cabinets, and the existing lineside circuits and equipment are all retained and interfaced to the TFMs, as their condition was not such a concern.

Adding layout complexity to an existing relay-based interlocking isn't always as easy as some may assume, even if the wiring is in perfect condition. As a 'parallel processing system', it is theoretically possible to add new circuits endlessly as desired but those have to mesh closely with whatever is already there and relays and wires must be housed on existing racks and in existing ducts and raceways. There isn't unlimited capacity, and even if a new room was erected next door for the new functions, their circuits would have to be closely entwined with the existing ones, which can run into space problems for the interconnecting cables and wires in the old room.

 

[Annetts key]

Adding layout complexity to an existing relay-based interlocking isn't always as easy as some may assume, even if the wiring is in perfect condition. As a 'parallel processing system', it is theoretically possible to add new circuits endlessly as desired but those have to mesh closely with whatever is already there and relays and wires must be housed on existing racks and in existing ducts and raceways. There isn't unlimited capacity, and even if a new room was erected next door for the new functions, their circuits would have to be closely entwined with the existing ones, which can run into space problems for the interconnecting cables and wires in the old room.

While this is true, the real reason these days is the time and cost. If extensive changes to a free wired route relay interlocking are required, and the existing installation has too much wiring with degraded insulation (or due to other practical reasons), then it may be possible to build a new route relay interlocking to replace the existing installation. But this is expensive compared to installing a computer based interlocking.

 

[MarkyT]

While this is true, the real reason these days is the time and cost. If extensive changes to a free wired route relay interlocking are required, and the existing installation has too much wiring with degraded insulation (or due to other practical reasons), then it may be possible to build a new route relay interlocking to replace the existing installation. But this is expensive compared to installing a computer based interlocking.

Faced with significant layout alterations required for a new Royal Mail terminal next to Bristol Parkway station, Railtrack was able to replace the interlocking at Stoke Gifford in the 1990s by wiring up a complete set of new relay racks, incorporating the changes, within the existing, unusually cavernous equipment room there. These could then be tested and debugged exhaustively offline before a fairly simple changeover was undertaken. Having to interface with the legacy E10K Integra control panel at Bristol no doubt had a part to play in the decision to do it that way. The brand-new Royal Mail hub lasted only a few years, but the layout and signalling changes enabled the early introduction of an additional passenger platform at Bristol Parkway after the hub closed. More recently, new processor-based signalling, controlled by workstations at Thames Valley Signalling Centre in Didcot, has been introduced, associated with the GWML electrification project and allowing a 4th platform to be added at the station.

 

[DelW]

Some more information on lineside works in the run up to the next closure. This must have been quite a large mail-shot, since I live around 400m from the line. I haven't heard any noise, though I've been away from home on most of the dates so far.