South Wales Main Line

South Wales Main Line
The entrance to the Chipping Sodbury Tunnel with the newly electrified overhead line equipment
Overview
StatusOperational
OwnerNetwork Rail
LocaleSouth Wales
South West England
Stations18
Service
TypeHeavy rail
SystemNational Rail
Operator(s)Transport for Wales
CrossCountry
Great Western Railway
History
Opened1850; 174 years ago (1850)
(Chepstow-Swansea)
1903; 121 years ago (1903)
(Swindon-Patchway)
Technical
Line length84 miles 30 chains (135.79 km)
Number of tracksMainly double track, though quadruple track from Severn Tunnel Junction via Newport to Cardiff Central.
CharacterMain line
Track gauge4 ft 8+12 in (1,435 mm) standard gauge
Electrification25 kV 50 Hz AC OHLE
(Wootton Bassett to Cardiff Central)
Operating speedUp to 125 mph (201 km/h) in England
Up to 100 mph (161 km/h) in Wales
Route map

(Click to expand)

The South Wales Main Line (Welsh: Prif Linell De Cymru), originally known as the London, Bristol and South Wales Direct Railway or simply as the Bristol and South Wales Direct Railway, is a branch of the Great Western Main Line in Great Britain. It diverges from the core London-Bristol line at Royal Wootton Bassett beyond Swindon, first calling at Bristol Parkway, after which the line continues through the Severn Tunnel into South Wales.

Much of the South Wales Main Line was built between the 1830s and 1886; originally trains to and from destinations in England ran via Chepstow, Gloucester and Stroud, joining the Great Western Main Line at Swindon. A more direct route was challenging yet desirable, leading to the construction of the line's most prominent civil engineering features, the Severn Tunnel. Completed in 1886, it permitted a significant reduction in journey times between various destinations, especially after the construction of the Badminton Line in 1903. During the British Rail era, the line was incorporated into the Western Region and steam locomotives were replaced by diesel locomotives, such as the Intercity 125 high speed trainsets. During the 2010s, the line between Swindon and Cardiff Central was electrified using the 25 kV AC overhead system as part of the wider electrification of the Great Western Main Line; this has permitted the operation of electric traction between Cardiff and London for the first time to commence in 2020.

Presently, Great Western Railway operates Class 800 trains between London and South Wales, and "Castle class" High Speed Trains on services between Cardiff and South West England. CrossCountry provides services from Cardiff to Nottingham via Severn Tunnel Junction and thence the Gloucester to Newport Line via Gloucester and Birmingham. Transport for Wales operates services between South Wales, and North Wales and the Midlands on the line. Operations are mostly managed from the Wales Rail Operating Centre in Cardiff; digital signalling is to be rolled out.