South Wales Main Line

The original route of the Great Western Railway (GWR) between London and South Wales, after the opening of Brunel's Chepstow Railway Bridge in 1852, left the Bristol-bound Great Western Main Line at Swindon, proceeding via Stroud, Gloucester and Chepstow before rejoining the present line at Severn Tunnel Junction. This gave rise to the nickname 'Great Way Round'.[1][2]

In 1886, the opening of the Severn Tunnel brought the opportunity of a more direct route to South Wales, and trains from Swindon to Newport and beyond were routed via Bath, Bristol and the tunnel.

The route used today was established in 1903 with the building of what is often known as the Badminton Line.[3] This involved the construction of about 33 miles (53 km) of new track, and tunnels at Alderton and Sodbury. The new line left the Bath line beyond Swindon at what is now Royal Wootton Bassett, rejoining the earlier route north of Bristol near Patchway. Not only did this provide a more direct route for traffic to and from South Wales, the gradients were easier for coal trains to negotiate, and it was thought that the line would be a boost to what was, at the time of building, the expanding port of Fishguard. This was the GWR's connection with trans-Atlantic ocean liner departures.

Electrification

See also: Proposed railway electrification in Great Britain

Electrification work at Cardiff Central in October 2019

The South Wales Main Line was one of the last of the major inter-city routes in Great Britain to remain un-electrified. The government announced in 2012 a scheme to electrify the South Wales Main Line as part of a wider scheme of electrification on the Great Western Main Line. The line from London to Cardiff was fully electrified by Christmas 2019.[5]

The Hitachi Super Express trains bought for Great Western inter-city services are predominantly electric units, but a portion of the fleet are dual power source electro-diesel bi-mode trains, which enabled services to operate before line electrification is complete. The bi-mode trains will allow inter-city services to continue to operate from London all the way to Carmarthen in the future. The Super Express trains were expected to bring an estimated 15% increase in capacity during the morning peak hours. Electrification cut journey times between Swansea and London by an estimated 20 minutes, although electrification will not extend west of Cardiff to Swansea, Carmarthen or Pembroke Dock, and services on the line to Brighton, Portsmouth Harbour and Taunton will continue to be operated by diesel trains, as the Bristol to Exeter Line and the Wessex Main Line will not be electrified.[6]

Four track railway approaching Cardiff from Newport, prior to electrification

There are four tracks from Severn Tunnel Junction through Newport to Cardiff Central, with two tracks on the remaining sections.[7] Multiple-aspect signals are controlled from several power signal boxes including Swindon, Bristol and two in Cardiff. Over the August Bank Holiday weekend 2016, control of the signals between Westerleigh Junction and Pilning was switched over to the Thames Valley Signalling Centre. These signals now carry the prefix 'BL'.

The maximum line speed from Wootton Bassett Junction to Coalpit Heath is 125 mph (200 km/h);[8] 90 mph (145 km/h) from Coalpit Heath to Newport; 90 mph (145 km/h) from Newport to east of Bridgend;[9] 75 mph (120 km/h) from east of Bridgend to Swansea Loop North junction (with a small section of 100 mph (160 km/h) track through Pyle station); and 40 mph (65 km/h) from Swansea Loop North Junction to Swansea.[7]

A diversionary route exists if the Severn Tunnel is closed. This takes trains from Severn Tunnel Junction to Gloucester, from where they can rejoin the main line either via the Golden Valley Line to Swindon, or take the Cross-Country Route and reverse at Bristol Parkway.

If the line is closed between Cardiff Central and Bridgend, an alternative route exists along the Vale of Glamorgan Line.

Half of peak High Speed Trains and most off peak trains continue from Cardiff Central to Swansea, with a few continuing to Carmarthen or in summer, Pembroke Dock.

The local service between Swansea and Cardiff is branded Swanline. The urban network within and surrounding Cardiff, including the Maesteg Line, is referred to as Valley Lines.

• On 7 March 2015, Battle of Britain-class locomotive 34067 Tangmere was hauling a charter train that overran a signal at Wooton Bassett, Wiltshire. The train's operator, West Coast Railway Company was temporarily banned from running trains on the British railway network as a direct consequence of this incident.

• Transport in Wales
• Transport in England
• South Wales Railway
• Great Western Main Line

• Network Rail Passenger Timetable. London: Network Rail. 2006.

Wikimedia Commons has media related to South Wales Main Line.

• 2007 Business Plan, Network Rail, London