The Branch Line Society


Southern Area Signalling Centres (ASC)
Saturday 30th April 2016


Originally advertised as a morning visit to Feltham; Victoria and Three Bridges ASCs were added to the day, enabling different generations of panel boxes dating from the mid 1970s onwards to be experienced and compared. 15 signalling aficionados met for 10.30 at Feltham station and took the short walk to the 1974-opened signalling centre. The smallest of the three visited, it was originally part of a BR 1970s scheme to signal the entire Southern Region from just 13 locations by the mid-1980s (the first box to be built was at Dartford). Feltham covers a large area previously signalled from many boxes by semaphores in south-west London and beyond mostly into Middlesex and Berkshire. It fringes with Wimbledon ASC towards London, at Chiswick, Richmond and Norbiton, Wokingham box at Bracknell, Woking ASC at Chertsey and Frimley as well as Acton Wells Junction signal box at Kew East Jn. The area is mostly two tracked with many level crossings and has frequent London Waterloo EMU services. Freight passes through the area towards the North London line at Kew East Jn, towards Clapham Junction, for the West London line, as well as towards Kent. Little has changed over the last 40+ years other than the removal of a few berthing sidings at outstations and various emergency crossovers. It is anticipated that signalling control will move to Basingstoke Rail Operating Centre (ROC) over the next few years. The first sign of this is the proposed automation of the Shepperton branch signalling next year.

During our visit train services were running very well despite heavy passenger traffic, requiring some additional trains, because of the Army versus Navy rugby matches at Twickenham. The party noted the crowd control arrangements there: all Up trains use the Up loop (P3) to avoid the possibility of both Up and Down trains disgorging large number of passengers onto the Up and Down main platforms (P4 & P5 island) together. This worked well and also applies after events. A train from Reading was losing time due to the large number of passengers; the conflicts this created at junctions were witnessed, and the resulting knock-on effects. After 90 minutes at the box and thanking the staff, members left for the station to experience the crowded trains, travelling via Twickenham to Clapham Junction for the second visit! Parts of the large former Feltham Yard site (closed 6 Jan 1969) had recently been cleared of trees, presumably for some sort of development.

At 12.30 the party met up again outside the 1980/92 Victoria ASC (at Clapham Junction!). On entering the building participants were struck by its sheer size, the scale of the operation (much greater than imagined) and the number of staff required. Some were changing shifts, which enabled observation of the two enormous concave panels facing each other and attempts to identify the locations from the track layouts. From our entrance point (the Victoria station end, the east side of the building) the Sussex route was on the right and Kent on the left. Splitting into two groups enabled each group to work along one side in detail, meet at the far end then work back along the other side. The Kent side covers from Victoria Eastern through to Swanley. Outside Victoria is Stewarts Lane depot area, where many lines are reversible and a variety of routings are available. Crews often request to run via a less commonly used route to keep up their knowledge! The Factory Jn area connections to Waterloo via the Stewarts Lane Viaduct to Nine Elms Jn are rarely used since the transfer of Eurostar traffic to St Pancras. Conversely, the connections via Longhedge Jn to the West London line (signalled from the Victoria Sussex side) and towards Clapham Junction (Wimbledon ASC) via the Ludgate lines now have 4tph each way since the introduction of the London Overground service to the East London line.

From Shepherds Lane Jn through to Swanley there is effectively a four (or more) track railway; two routes split at Brixton to run via Herne Hill or Nunhead and Catford recombining at Shortlands Jn. It is important that trains be correctly routed through this section to minimise delays. This area is split between several signallers so close liaison is needed to keep everything running smoothly. There are many junctions to swap trains between fast and slow lines but several include switch diamonds which are sensitive to hot weather with expansion, so are not used at certain times of the year.

At St Mary Cray Jn and Bickley Jn and there are connections to Petts Wood and Chislehurst (Ashford IECC). Demonstrations were given on how the interface with Ashford IECC worked on the reversible lines. A release has to be obtained before movement with a direction of flow arrow showing which way the move is taking place. Beyond Swanley Jn, where the line splits towards either Rochester (East Kent IECC) or Otford (Ashford IECC), was Fawkham Jn and the now OOU connection to HS1. From the Southfleet Jn end, this line is now used as sidings for secure storage of original Eurostars. There is insufficient siding space available at Temple Mills depot since the new units had been delivered.

The Central side towards London was far quieter than usual due to resignalling commissioning with transfer of the Streatham area to Three Bridges ROC. This had started from the Friday close of service a few hours before our Spring Bank Holiday weekend visit! The panel's country end covers Sutton radiating from the Wallington area to Epsom Downs, Wimbledon and Ewell West. This is expected to be the next transfer to Three Bridges ROC in 2017/18. A large blank area on the panel was where the Wimbledon to West Croydon via Mitcham Junction line had been removed in 1997 on closure to become part of Tramlink. Moving along the diagram the four-track main line, Balham (excl) to Norbury section was under possession along with Streatham to Streatham South Jn for the resignalling and transfer of control as mentioned. From Balham via Streatham Hill towards Crystal Palace was the only route open for traffic with many fewer paths available. These were just the Thameslink route trains via Tulse Hill and a quarter hourly service from Victoria (most trains to/from Brighton, Littlehampton and Eastbourne etc used London Bridge instead). The signaller covering this area also had additional work because a track defect had recently been reported in Streatham Hill tunnel; trains had to be advised to run cautiously through it until inspection and any rectification work needed had been undertaken.

Continuing to London, the Clapham Junction to Victoria section was remarkably quiet because of the engineering work but the Central side London end also controls the West London line signalling linking to Mitre Bridge Jn (Wembley SCC). Its traffic has dramatically increased in recent years with a regular service of 5tph both ways, and many freight workings, as the line links to many other parts of the London area. The reversible signalling is only generally used during disruption to keep trains moving. No set time had been allocated for our visit and it was surprising how quickly the 2½ hours went here.

Then it was back to Clapham Junction station to travel to the 1982/2013 Three Bridges ASC. The journey via Streatham Hill was delayed due to the track defect cautioning at Streatham Hill, missing a rather optimistic connection at East Croydon. At Three Bridges there was direct access off P5 to the ASC which was reached at 16.50. The Shift Manager gave a quick briefing before having to return to his duties because of multiple incidents. The main signalling diagram is in a very large horseshoe shape giving a very airy and spacious feel to the operating floor. From the left the routes towards Victoria and London Bridge combined at Windmill Bridge Jn. Both of these lines are now controlled from Three Bridges ROC (in the fork of the Horsham and Brighton lines, the other side of the main line). The Brighton main line route then occupies the whole diagram to the far right hand side (Brighton station). Branches at South Croydon towards Oxted, at Purley to Tattenham Corner and Caterham, Redhill towards Godstone and at Three Bridges towards Crawley and Horsham are also controlled from this centre. Along and behind the open part of the horseshoe, a much newer separate panel, facing inwards, controls Dorking (excl) to Arundel (excl) via Horsham linking to the main panel. Using axle counters, it took over from the manual signalling of the Arun Valley line, a project completed in 2013.

From Balcombe Tunnel Jn to Preston Park the route has 'SimBiDS' (Simplified Bi-Directional Signalling) but because of restrictions imposed following a head-on collision at Copyhold Jn many years ago, it is now only generally used in emergency or during overnight engineering works.

Other locations the ASC links to are the depots at Selhurst (suburban fleet and DMUs), Brighton Lovers Walk (mostly main line fleet) and the massive, recently completed Three Bridges depot complex (just south of the signalling centre) for the new Thameslink Class 700 EMUs. The Copyhold Jn (Haywards Heath) to Ardingly stone terminal single line electric token block was demonstrated to our members.

During the visit there were various incidents which were all dealt with in an impressively calm and controlled fashion but enabled members to experience some of the problems that can, and do, occur throughout the railway system. There was congestion at East Croydon; a passenger was taken ill delaying trains at Purley and a track defect at Redhill caused a track circuit fault requiring trains to be talked past red signals with manual setting of routes until it was cleared. Another track fault at Gatwick Airport closed the Up fast (P4) line all day. A trespass at Whyteleafe South required a few trains to be cautioned until the person had returned to the platform (a similar incident also occurred at Peckham Rye during the Victoria visit), demonstrating that delays are not always the fault of the railway. Finally, a train approaching a red signal at Tinsley Green Jn travelling just slightly over the permitted speed activated the TPWS equipment, which stopped it safely, requiring the Three Bridges supervisor to question the driver (over the GSM-R) and fill in a form about all the circumstances.

Most participants returned towards London but your reporter made a quick trip to Haywards Heath to view the new units in the depot. On returning the rare Up Fast to Up Loop Tinsley Green Jn crossovers and Earlswood Up Slow to Up Quarry crossovers were experienced to bypass the Gatwick Airport P4 closure. Then to London Bridge for yet another different route into the Central side of the station and to observe the rebuilding progress on the Eastern side and approaches. Thanks in particular to our member Jon King for arranging these excellent, interesting and most instructive visits.