HomeRail NewsPutting the Paisley Corridor into the WSSC

Putting the Paisley Corridor into the WSSC

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The new generation of Network Rail Control Centres are growing by number every year, but one of the first to be commissioned has recently had a major expansion to its operational area.

The West of Scotland Signalling Centre (WSCC), sited at Cowlairs on the outskirts of Glasgow, first opened in December 2008 when the old Glasgow Central Power Box signalling area transferred to it.

Constructed in the architectural style that all subsequent centres have followed, the building combines functional needs with high security. The track layout changes at that stage were minimal.

This establishment of the control centre, and the subsequent provision of two additional platforms at Glasgow Central Station followed by a complex interlocking renewal at Shields Junction, paved the way for a complete upgrading of the line onwards to Paisley.

The Paisley Corridor

Plans were well developed in 2006 for a rail link to serve Glasgow Airport by building a 2km spur running northwards from the Paisley – Gourock line. Known as GARL, the envisaged train service necessitated an increase in line capacity on the route into Glasgow.

The line from Shields to Paisley had originally been four track but this had been rationalised down to two as part of the electrification in the late 1960s.

Whilst the GARL project was eventually abandoned owing to the high cost of overcoming significant obstacles along the proposed route (fuel tanks, the bridge over the M8, a 2km viaduct over playing fields), it was agreed that the line capacity improvements should continue as rising passenger numbers required an enhanced train service to the commuter belts in Ayrshire and Inverclyde as well as the regular freight services along the route.

The most significant freight is the carriage of coal from the port at Hunterston to a number of power stations including Longannet via the recently opened Stirling – Alloa – Kincardine line.

As the second busiest line in Scotland, the existing layout was seriously inadequate with a particular bottleneck just eastwards of Paisley Gilmour Street station. This ‘Paisley Corridor’ improvement thus got the go ahead and work started in 2009.

The main thrust has been to lay an additional track westwards from Shields and to increase this to four tracks in the immediate Paisley area so as to separate the junction for the Inverclyde and Ayr lines away from the station throat.

All lines will be made reversible but only the middle track will use the facility on a regular basis so as to achieve an increase in directional capacity for the morning and evening peaks.

A complete new signalling system was required for all of this, so as to add the area onto the WSSC. This plan, however, also included the complete closure of Paisley Power Box and the transfer the existing 10 remote relay interlockings between Paisley and Ayr to the control of WSSC.

As part of this, signalling alterations were needed to control an extended loop at Elderslie and provide a new cross-over at Brown Street, just west of Paisley.

The intensity of the train service, being both daily commuter traffic to Glasgow, leisure journeys to the Ayrshire coast and the strategic importance of the freight traffic, meant that any long term blockade would not be allowed, with the work having to be done during 29 hour Sunday possessions and the occasional 54 hour weekend shut down. This added to the cost but was in keeping with Network Rail’s declaration to restore a seven day railway.

Balfour Beatty were given the contract for the permanent way, civils and OLE work, Invensys provided the new signalling and GE Transportation provided the control system and two new signaller workstations for the Paisley and Ayr control areas.

The work involved was massive and included 15 kilometres of new track, 40 new point ends, 17 new signalling gantries and 423 new overhead line foundations to rebuild the overhead line electrification system, all of which had to be installed in a tight clearance envelope and limited hours of work. Meticulous planning was essential.

West of Scotland Signalling Centre

The heart of the new signalling is the Invensys Westlock computer based interlockings. These are second generation technology taking over from the original SSIs pioneered by BR, Westinghouse and GEC in the 1970s.

Having much greater processing capacity, relatively few modules are required for even a complex area like Glasgow. Using the time honoured 2 out of 3 principle, the interlockings are rated SIL4 in the safety table and have performed reliably since their introduction some 4 years ago at Leamington Spa.

Separate Westlocks are provided for the Glasgow Central, Shields and Paisley areas. An internal transmission system connects the interlockings to the GE MCS control system and onward to the operating floor, where the layout comprises a number of VDU based signallers’ desks and supervisor positions.

There is no hard wired signalling panel since these are difficult to alter as further expansion and alterations take place. As one signaller said, “the overview is not as good but you eventually get used to it”.

Distributing the interlocking commands to the external signals, points, level crossings, etc uses 64kbps circuits within the telecoms FTN network, these being both available and resilient. The comment is made however that this arrangement is becoming obsolete, the use of IP addressing being likely to succeed it in the near future. The FTN is also used for connecting to the relay interlockings on the Ayr and Inverclyde lines.

LED signals predominantly mounted on gantries have been used on the Paisley Corridor section with four lightweight VMS signals being used to overcome construction limitations and excessive cost on the St James viaduct.

Unaltered points use the reliable Alstom HW2000 machine whilst the new layout introduced Hy-Drive points. Trackside power is by means of a double end fed, single phase 650v feeder cable serving REBs and lineside locations

Also commissioned during the time of WSCC has been the GSM-R track to train radio network, the first use of this system in the UK which will eventually be adopted nationwide.

The quality of the speech is reckoned to be markedly better than the Cab Secure Radio that had been in use. Siemens HiPath concentrator equipment is used to terminate the SPTs which continue to be provided at every signal, although with the introduction of GSM-R radio, decreasing use is made of these.

The WSSC does not yet use Automatic Route Setting (ARS) but the facility will become available later in 2012. A separate training room has screens that mirror the main operational displays and can be programmed to reflect any disruption that the signaller is likely to encounter.

Without ARS, the signallers have to set routes for the main junctions and this keeps them familiar with the skills needed. Once ARS is introduced, the routes will be set automatically from the timetable data and thus the need for refresher training becomes necessary to ensure signallers can manage disruptive occurrences that need manual intervention.

The training period needed to become a signaller from scratch is around 16 weeks with a further element of ‘over the shoulder’ familiarisation before being allowed to work independently on a control desk. Part of the training includes psychometric testing to make sure signallers have the right relationship, planning and communication skills.

The Paisley Corridor and the extension of existing signalling control on the Ayr and Inverclyde lines were commissioned over the Christmas 2011 period under a 120 hour possession.

All signal commands and train movements are recorded so that if any untoward incident occurs, a full analysis of what took place can be made. This can show up equipment failures as well as human errors. Recordings are kept for 28 days.

Future Plans and New Networking Opportunities

The size of both the WSSC equipment room and operating floor demonstrates that many more sections are to be added to the control area under a strategic plan. The next stage will see the Glasgow South Suburban lines transferred covering the area controlled from Cathcart signal box.

This is planned to take place in April 2013 and will involve track layout changes to reinstate a double junction to replace the existing single leads. After that will be the transfer of the existing Motherwell Power Box area, extending the WSSC control almost to Carlisle.

The Westlock equipment is designed to interface to any future ERTMS aspirations on the WCML, which is designated as an EU TENS route. Thereafter, further extensions will include transferring the control of the Yoker box area.

Another challenge will be the provision of telecommunications links to lines not equipped with power signalling, such as the Glasgow – Barrhead – Kilmarnock and the Stranraer lines.

Again, Scottish ingenuity is coming up with a solution. The FTN, being primarily designed to support the GSM-R network, does not necessarily have its terminating points (Points of Presence – PoP) near to signal boxes, and thus the ability to get high quality data connections is that much harder.

The Rail Engineer reported on plans for a Scottish IP network in October 2010 (issue 72), and Network Rail engineers are experimenting with using legacy infrastructure to get IP facilities to the remoter places at a reasonable cost.

Extending out from the PoP with an MPLS connection over whatever cable plant is available seems to be practical and this can be done for about £10,000 per site as against £70,000 for an FTN node.

Potentially this will allow old signalboxes to have modern datacom facilities, not necessarily meaning they can be abolished, but allowing them to be part of the sophisticated decision making processes that modern control centres utilise in the goal for operational efficiency.

The Scottish IP network is expected to be rolled out to all but the remotest of lines covering 285 stations by 2015. With the new Network Rail Telecom (NRT) organisation in place, it is likely that this Scottish initiative will become a standard for adoption elsewhere.

Those of us who were young engineers in the 1960/70s, and who thought the power boxes of that era were the ultimate in technology, now realise that nothing stands still. These latest control centres will be equally antiquated in 40 years time, when lineside signals become a thing of the past. Maybe even ERTMS will also be past its sell by date by then.

Thanks are expressed to Colin Findlay, Ian Findlay, Matthew Spence, Alan Taylor from Network Rail and to Peter Allan from Invensys for facilitating the visit and for willingly explaining all the technicalities.

Clive Kessell
Clive Kessellhttp://therailengineer.com
SPECIALIST AREAS Signalling and telecommunications, traffic management, digital railway Clive Kessell joined British Rail as an Engineering Student in 1961 and graduated via a thin sandwich course in Electrical Engineering from City University, London. He has been involved in railway telecommunications and signalling for his whole working life. He made telecommunications his primary expertise and became responsible for the roll out of Cab Secure Radio and the National Radio Network during the 1970s. He became Telecommunications Engineer for the Southern Region in 1979 and for all of BR in 1984. Appointed Director, Engineering of BR Telecommunications in 1990, Clive moved to Racal in 1995 with privatisation and became Director, Engineering Services for Racal Fieldforce in 1999. He left mainstream employment in 2001 but still offers consultancy services to the rail industry through Centuria Comrail Ltd. Clive has also been heavily involved with various railway industry bodies. He was President of the Institution of Railway Signal Engineers (IRSE) in 1999/2000 and Chairman of the Railway Engineers Forum (REF) from 2003 to 2007. He continues as a member of the IRSE International Technical Committee and is also a Liveryman of the Worshipful Company of Information Technologists. A chartered engineer, Clive has presented many technical papers over the past 30 years and his wide experience has allowed him to write on a wide range of topics for Rail Engineer since 2007.


  1. So, what became of the loop through old industrial lines under Renfrew Road, under the stream and under the airport (where you build an underground station) to resurface near the crossing with the M8 sliproad and back in through St James station? Surely the simplest way is the best way in this instance?


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