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40% (3,062 miles / 4,928 km) of the British rail network is electrified and 60% of all rail journeys are by electric traction (both by locomotives and Multiple Units).

Railway electrification as a means of traction emerged at the end of the nineteenth century. It offered several benefits over the then predominate steam traction, particularly in respect of its quick acceleration (ideal for urban (metro) and suburban (commuter) services) and power (ideal for heavy freight trains through mountainous/hilly sections). A plethora of systems emerged in the first twenty years of the twentieth century (as listed below). In 1928 a government committee agreed 1500 V DC overhead as the national standard, although little work was done to implement this and the plethora of different systems continued to exist (and even expand). Post World War Two, with nationalisation (1948), British rail expanded electrification (1500 V DC and the Southern third rail) but soon (mid 1950s) adopted 25 KV AC overhead for its proposed mainline electrification. Over the years of minimal capital investment the 25 KV AC network has expanded although large areas of the country are still non electrified, despite their urban, suburban, hilly or intercity nature.

Rail based (Third and Fourth rails)

650 to 850 V DC Third rail

• LWSR / Southern Railway / Southern Region of British Railways - everything but a few freight branches, Marshlink, North Downs Line, Uckfield branch of the Oxted Line and services through Salisbury.
• Northern City Line - ECML to Moorgate - A former main line taken over by the Underground and turned into a tube line. It was however isolated by the abandonment of the 1930s "New Works" programme (and the development of the greenbelt). Tube services were further truncated by the new Victoria Line in 1964 (which shortened the northern end of the line). The remainder was handed over to BR in 1975 in conjunction with electrification of ECML to allow dual voltage (ie both 25Kv AC Overhead and Third Rail DC) commuter trains into London. A link with the ECML was made to enable this. Presumably third rail was chosen as the tunnels were of too narrow a bore to allow overhead lines to be installed (as they are on the Snowhill, Thameslink route.)
• Merseyrail Electrics (Merseyrail) - A history can be found here. See also
• Glasgow Subway ?
• Tyneside Electrics - 630V DC(de-electrified by BR in 1960 then turned into Tyne and Wear Metro )

• Docklands Light Railway (bottom contact third rail)

630 V DC Fourth Rail

• London Underground
• LNWR - London suburban network - Euston and Broad Street to Watford Junction, Croxley Green and Richmond ( North London Line and Watford DC Line ). A short history can be found here.

The Watford DC Line between Queens Park and Harrow & Wealdstone is peculiar in that it is used by both Silverlink Metro trains, designed for 750V third rail, and Bakerloo Line trains designed for 630V third and fourth rail. Consequently the voltage is set at a suitable compromise value around 690V nominal, and the centre rail is at the same potential as the return running rail, whereas in normal London Underground usage the traction supply floats with the centre rail at nominally -230V and the outer rail at nominally +420V. giving 630V overall.

1200 V DC Side Contact rail

• Manchester Victoria - Bury This very busy commuter line was electrified by the Lancashire and Yorkshire Railway in 1913 to 3500 V DC overhead (see above). In 1917 the L&YR converted it to side contact third rail. This system was abandoned when the line was converted to become part of the Manchester Metrolink. and

Overhead

1500 V DC Overhead

In the wake of World War One, the British Government set up a committee to investigate the various systems of railway electrification and in 1928 it reported that 1500 V DC overhead should be the future national standard. Several schemes (see below) were implemented in its wake, although the Great Depression and World War Two meant very little work was done. Technological advances post war saw a government U turn and the 25KV AC system was adopted instead for the West Coast Main line and Glasgow suburban electrification as set out in the 1955 BR modernisation plan - at the same time the large amounts of money had/were still being spent converting several lines to 1500 V DC.

• Manchester, South Junction and Altrincham Railway - A joint LMS and LNER effort, opened on the 11th May 1931, it was a test bed for both companies for the new standard (which at the time had not been implemented in the UK) in this largely self-contained busy suburban line. The success of this scheme propelled LNER's latter electrification efforts. The line was latter converted to 25 KV AC in 1971 but then parts converted to the Manchester Metrolink (a tram system).

• Manchester-Sheffield-Wath line. Known as the Woodhead Route. LNER, chose this hilly and busy mainline for its first mainline electrification, with work starting in 1936 . Due to the depression and World War Two it wasn't completed until the 1950s. However upon completion the government chose to utilise 25KV AC instead, leaving the few 1500v DC lines isolated and non-standard. Subsequent BR rationalisation (the Beeching Axe) saw large parts of this route closed east of Hadfield in 1981 (in favour of a route with more local communities). The remaining stub in Manchester was converted to 25 kV AC in December 1984.

• Shenfield Metro (Great Eastern Main Line) - Electrified post war (early 1950s), although LNER had been planning this since the early 1930s. It was soon converted to 25 kV AC, initially with some sections at 6.25 kV, in wake the 1955 BR Modernisation plan.

• Newport (near Sunderland) to Shildon (County Durham) line. In the wake of the electrification of Tyneside by the NER, this coal carrying line was electrified, as a precursor to electrifying NER's busy York to Newcastle mainline (Part of the ECML). It was dismantled by LNER around 1334/1935. , , , ,

• Tyne and Wear Metro Despite the abandonment in favour of 25KV AC overhead in the 1950s, large parts of the former "Tyneside Electrics" routes (which had been electrified using third rail until the 1960s when BR discontinued the "non standard" equipment in favour of Diesels) were rebuilt as the "Tyne and Wear Metro" in the 1970s. Styled as "Light Rail" it is in practice normal heavy rail, and even shares some lines with the current rail network (unlike the other tram systems in the UK which operate alongside but on separate rights of way).

3500 V DC Overhead

• Bury to Holcombe Brook This was electrified by the Lancashire and Yorkshire Railway in 1913 as part of a trial system for export. The system was converted thrid rail in 1917 (see above).

6600 V (6.6 kV) AC Overhead @25 Hz

• LBSCR
• Lancaster to Heysham via Morecambe (Morecambe Branch Line)

6250 V (6.25 kV) AC Overhead @50 Hz

• Shenfield Metro (Great Eastern Main Line) - since converted in stages to 25 kV
• Parts of Glasgow Suburban (see SPT and Transport in Glasgow)

During the initial electrification of parts of the network to 25 kV AC overhead the initial solution to the limited clearance problems in suburban areas (due to numerous tunnels and bridges) - notably London and Glasgow - was to use the lower voltage of 6.25 kV AC Overhead. Latter technological improvements allowed these area to be converted to 25 kV AC Overhead.

25000 (25 kV) AC Overhead @50 Hz

• London, Tilbury and Southend (LTS) - converted from 6.25 kV AC overhead
• Great Eastern Main Line (GEML) - converted from 6.25K V AC overhead and 1500 V DC overhead
• East Coast Main Line (ECML) - in the 1980s
• Midland Main Line (MML) (south of Bedford) - in the 1980s
• West Coast Main Line (WCML) - in the 1950s under the 1955 BR modernisation plan to Birmingham (new Street) / Liverpool (Lime Street) / Crewe / Manchester (Piccadilly). Extended in the 1970s to Glasgow. The branch to St Albans was electrified by Network South East 1987-88. In 2003 Crewe to Kidsgrove section of the Crewe to Derby Line was electrified as a diversionary route for the WCML.
• Glasgow Suburban (see SPT and Transport in Glasgow) - started in the 1950s under the 1955 BR modernisation plan.
• Leeds area - Leeds to Skipton (Airedale Line), Leeds to Bradford (Wharfedale Line) and Leeds branch off the ECML (via Wakefield Westgate) (1980s/early 1990s)
• Manchester area - Manchester to Glossop / Hadfield (converted from the truncated 1,500V DC Manchester-Sheffield-Wath electric railway), the Manchester, South Junction and Altrincham Railway (although part of this line was converted to the Manchester Metrolink) and the Manchester Airport Line (although primarily operated by diesel multiple units)
• Birmingham area - Birmingham Cross-City Line and part of the Chase Line (1980s/early 1990s) and branches into the West Midlands of the WCML
• Great Western Main Line (GWML) (only between Heathrow and London Paddington - see Heathrow Express and Heathrow Connect)
• Channel Tunnel Rail Link (CTRL) - employing auto-transformers
• Crossrail (Proposed)

See also

• Railway electrification system
• Railroad electrification in the United States
• List of current systems for electric rail traction

External links

• Electric rail transport
• Rail infrastructure
• Rail transport in Great Britain