Railway electrification in Great Britain

Railway electrification in Great Britain describes the past and present electrification systems used to supply traction current to railways and tramways in Great Britain with a chronological record of development, a list of lines using each system and a history and a technical description of each system.

History
Railway electrification emerged at the end of the 19th century. This had many advantages over the then predominant 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). Many systems emerged in the first twenty years of the 20th century. In 1921, a government committee chose 1,500 V DC overhead to be the national standard but little implementation followed and many different systems co-existed.

After World War II and the nationalisation of the railways in 1948, British Railways expanded electrification of both the 1,500 V DC overhead and Southern Region third rail systems but, in 1955, adopted 25 kV AC overhead for its proposed main line electrification.

Despite the following years of minimal capital investment, the 25 kV AC network has continued to expand, slowly, although large areas of the country outside London are still non-electrified, despite their urban, suburban, hilly or intercity nature.

The British government's preferred option was to use diesel trains and run them on biodiesel. In the 2007 White Paper Delivering a Sustainable Railway, the government ruled out large-scale railway electrification in Network Rail's Control Period 4.

However, since then, with a new Network Rail Chief Executive, Iain Coucher and a new Transport Minister Lord Adonis (subsequently Secretary of State for Transport), the outlook has changed considerably. In May 2009, Network Rail launched a consultation on large scale electrification, potentially to include the Great Western Main Line and Midland Main Line. Alongside major projects like these would be a raft of smaller "in-fill" schemes. Key benefits cited in the consultation were that electric trains are faster, more reliable and cause less track wear than diesel trains.

In Scotland, where transport is a matter devolved to the Scottish Government, Transport Scotland is extending electrification where appropriate, for example on the Airdrie-Bathgate Rail Link and Glasgow Airport Rail Link. This is part of a larger plan that foresees many major routes in Central Scotland electrified including the main Edinburgh to Glasgow Queen St route.

Facts and figures


In 2006, 40% (3,062 miles / 4,928 km) of the British rail network was electrified and 60% of all rail journeys were by electric traction (both by locomotives and multiple units)

According to Network Rail, 66% of the electrified network uses the 25 kV AC overhead system and 36% uses the 660/750 V DC third rail system.

Systems no longer used
Great Britain has used a number of different electrification systems in the past. Many of these date from the early part of the 20th century when electricity was being experimented with for traction purposes. This section describes each system, in order of increasing voltage.

500 V DC, Overhead

 * Grimsby and Immingham Railway

525 V DC, Third Rail

 * Liverpool Overhead Railway
 * The Liverpool Overhead Railway was one of the earliest electric railways in Great Britain. The first section between Alexandra Dock and Herculaneum Dock was opened in 1893. The line connected with Lancashire and Yorkshire Railway's North Mersey Branch. It was never nationalised and it closed on 30 December 1956 due to extensive corrosion throughout its iron infrastructure, which was deemed uneconomical to replace.

600 V DC, Third Rail

 * Tyneside Electrics


 * This was electrified in 1904, in response to extensive competition from new electric trams. The concept was a success for the North Eastern Railway (NER) a noted early pioneer in electrification, as passenger numbers returned to pre Tram levels. As the stock reached life expectancy in 1937, the network was remodelled by London and North Eastern Railway (LNER) to reflect the changing industrial and residential makeup of the area. Electrified at the same time was the dockside branch, where a pair of Class ES1 (formerly NER No.1 and 2) locomotives were introduced from 1905. These British Thomson-Houston locomotives operated from both the third rail and from overhead catenary. British Rail brought in third-rail stock (12 2EPBs) from the Southern Region in 1955. The system was de-electrified by British Rail in between 1963 and 1967, citing the changing industrial and population makeup of the area, reducing the need for electric traction. Much of the Tyneside network was re-electrified using 1500 V DC overhead (see below) as the Tyne and Wear Metro.

650 V DC, Overhead

 * Swansea and Mumbles Railway

1,200 V DC, Third Rail (Side-Contact)



 * Manchester Victoria - Bury
 * In 1917, the line between Manchester Victoria and Bury was electrified using 1,200 V DC third rail (side contact). The line between Bury and Holcombe Brook that had been electrified using 3,500 V DC overhead in 1913 was converted to this system in 1918.  This system was abandoned in 1991 when the line was converted to 750 V DC system and became part of the Manchester Metrolink

1,500 V DC, Overhead
In the wake of World War I, the British Government set up a committee to investigate the various systems of railway electrification and, in 1928, it reported that 1,500 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 II meant very little work was done. Technological advances post-war meant the 25 kV AC system was adopted instead, for the West Coast Main line and Glasgow suburban electrification, as set out in the BR 1955 Modernisation Plan - at the same time the large amounts of money had/were still being spent converting several lines to 1,500 V DC.


 * Manchester, South Junction and Altrincham Railway
 * A joint LMS and LNER effort, opened on 11 May 1931. The success of this scheme propelled LNER's later electrification efforts. The line was converted to 25 kV AC in 1971 but the stretch between Altrincham and Trafford Bar plus the stretch between Trafford Bar and the Cornbrook viaduct were later incorporated into Manchester Metrolink and converted again, to 750 V DC.


 * Manchester-Sheffield-Wath
 * Known as the Woodhead Route. The LNER chose this hilly and busy mainline for its first mainline electrification, with work starting in 1936. Due to the depression and World War II, it was not completed until the 1950s.  On completion, the government chose to standardise on 25 kV AC instead, leaving the Woodhead Route and the few other 1,500 V DC lines isolated and non-standard.  In subsequent rationalisation by BR, much of this route closed east of Hadfield in 1981 in favour of the more southerly Hope Valley Line, which serves more local communities.  The remaining stub in Manchester was converted to 25 kV AC in December 1984.


 * Shenfield Metro
 * LNER decided to electrify the Liverpool Street to Shenfield section of the Great Eastern Main Line (GEML), known as the Shenfield Metro. Civil engineering works began in the 1930s but World War II intervened. Work was completed in 1949 and extended to Chelmsford and Southend (Victoria) in 1956 using Class 306 (AM6) EMUs. It was converted to the new standard of 25 kV AC, initially with some sections at 6,250 V, on 4—6 November 1960, in the wake of the BR 1955 Modernisation Plan that called for 25 kV AC to be the new standard. The rest of the GEML was subsequently electrified.


 * Shildon to Newport
 * This line ran from Shildon (County Durham) to Newport (near Middlesbrough). The route was initially over the 1825 Stockton to Darlington line, then via Simpasture Junction, the ex-Clarence railway through Carlton, Carlton Junction to Carlton South Junction, Bowesfield West Junction to Bowesfield Junction, through Thornaby and ending at Erimus yard Newport East. In the wake of the electrification of Tyneside by the NER, this coal-carrying line was electrified between 1 July 1915 and 1 January 1916, as a planned precursor to electrifying NER's busy York to Newcastle main line (part of the ECML). The electrification system was removed by the LNER (between 7 January 1935 and 8 July 1935) due to the decline in the coal market making it uneconomic to undertake the significant renewals required to continue electric operation. The locomotives were stored for other electrified routes.

3,500 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 to third rail in 1918 (see above).

6,250 V 50 Hz AC, Overhead
During the initial electrification of parts of the network to 25 kV 50 Hz AC overhead the initial solution to the limited clearance problems in suburban areas (due to numerous tunnels and bridges) in London and Glasgow was to use the lower voltage of 6,250 V. Latter technological improvements in insulation allowed these areas to be converted to 25 kV. The last sections of 6,250 V were converted in the 1980s and this system of electrification is now obsolete in the UK.


 * London, Tilbury and Southend (LTS)
 * The majority of the line was electrified at 6,250 V in the early 1960s. Some sections were electrified using 25 kV from the outset. The sections electrified at 6,250 V were converted to 25 kV in the early 1980s.


 * Shenfield Metro
 * The line was originally electrified at 1,500 V DC overhead in the 1950s. In the early 1960s, the line was converted to 6,250 V AC overhead. In the early 1980s, the line was converted for a second time, to 25 kV.


 * Glasgow Suburban network
 * The majority of the network was originally electrified at 6,250 V in the early 1960s. Some sections were electrified using 25 kV from the outset.  The sections electrified at 6,250 V were converted to 25 kV in the early 1980s.
 * North Clyde Line - the central area, Springburn, Bridgeton and Milngavie branches and the Yoker loop)
 * Cathcart Circle Line
 * See SPT and Transport in Glasgow

6,600 V, 25 Hz AC, Overhead

 * Lancaster to Heysham via Morecambe (Morecambe Branch Line)
 * LBSCR's 'Elevated Electric' London suburban lines

110 V DC, Third Rail
Volk's Electric Railway was originally electrified at 50V DC. This was raised to 160V in 1884, and then reduced to the present 110V DC in the 1980s.

250 V DC, Third Rail

 * Hythe Pier Railway, electrified in 1922.

600 V DC, Third Rail

 * Glasgow Subway, electrified in 1935.

630 V DC, Fourth Rail




The London Underground is a large metro system operating across London, and beyond, commonly known as "the Tube". The 408 km (253 miles) network is made up of 12 lines and has been electrified for some time, starting in the 1890s. The network was largely unified between 1900–1910 and nationalised in 1933 becoming the railway component of London Transport (LT). A major expansion programme, the "New Works", was immediately launched, in which LT took over several urban branches of mainline railways.

The London Underground network has historically been located in north London, its expansion into south London was limited by geology unfavourable to tunnelling and by the existing extensive above-ground railway network in the area much of which was being electrified (see "Southern Electric").

Due to the early pioneering work by the City & South London Railway (now part of the Northern line), the Underground uses a relatively obscure four rail system of electrification. Two standard gauge rails are the running rails; the outer third rail carries positive current at +420 V DC, while the inner fourth rail is the negative return at –210 V DC, giving a supply voltage of 630 V DC.

The main advantage of the fourth rail system is that, in tunnels with metallic linings (usually cast-iron), the return traction current does not tend to leak into the linings and cause electrolytic corrosion there or in neighbouring utility metal mains. The two running rails are also available exclusively for signalling track circuits.

The surface sections of the lines use the fourth rail solely for operational consistency. The system shares track with Network Rail in several places. Some of these are non-electrified sections of the national railway network (e.g. Chiltern Railways out of Marylebone station) and diesel trains are used (by Network Rail). The suburban network of London North Western Railway (LNWR) was electrified in co-operation with London Underground but, in the 1970s, British Rail introduced third-rail EMUs and the sections of the LNWR suburban network not used by the Underground had the fourth rail removed (see London and North Western Railway section below).

650 V - 850 V DC, Third Rail "Southern Electric"


The LSWR third rail system at 660 V DC began before World War One from Waterloo to various suburban destinations. The Southern Railway was one of the companies formrf in the 1923 grouping and it adopted the LSWR system, by 1929 the LBSCR suburban overhead network was replaced by third rail. The South Eastern Main Line was electrified at 600 V but later upgraded to 750 V DC. The third rail extended throughout most South London lines under Southern control (LBSCR and SECR), then out of all its London termini. The 1930s there was much main line electrification including the Brighton mainline including East, West Coastways and related routes (1932/33), and the Portsmouth Direct Line (4 July 1937) and the Mid-Kent Line to Maidstone and Gillingham (1939).

After World War Two electrification was soon resumed under the newly nationalised British Rail's southern region. The BR 1955 Modernisation Plan included the two-stage "Kent Coast Electrification". The Chatham mainline was completed, then the SER mainline and related lines. At this time, the voltage used was changed from 660 V to 750 V. Since then, all further electrification has used 750 V but the lines electrified before this time remain at 660 V. Attention then switched to the neglected LSWR region (now titled the South Western Division). The South Western Main Line (SWML) to Southampton and Bournemouth was electrified in 1967, as was the Island Line.

Under sectorisation in the 1980s, Network SouthEast conducted extensive infill electrification. The SWML was completed to Weymouth 1988. The Snow Hill tunnel was reopened, enabling Thameslink. The Hastings Line, Eastleigh to Fareham Line, Oxted Line - East Grinstead branch were also electrified. This left only a few generally isolated, rural lines and freight branches un-electrified (West of England Main Line, North Downs Line, Marshlink Line, and Oxted Line - Uckfield branch).

650 V - 850 V DC, Third Rail, Other

 * Merseyrail
 * This uses 750 V.  A history is here


 * London and North Western Railway
 * Euston and Broad Street to Watford Junction and Croxley Green (Watford DC Line)
 * Richmond - North Woolwich (North London Line)
 * A short history is here. In 1970 the North London DC lines and the Class 501 EMUs used on these services were converted for third rail operation, with generally the fourth rail being removed on sections of lines not used by LUL. Some fourth rail was retained in the Gunnersbury and Queens Park areas for emergency use by LUL. With the closure of Broad Street, the NLL was joined with former Broad Street to North Woolwich via Stratford line, to extend the NLL: this section was electrified with third rail and OLE as far as Stratford and just third rail to North Woolwich. Two branches off the Watford DC Line have been closed; to Rickmansworth in 1952 (to passengers, goods 1967) and to Croxley Green in 1996.


 * The Watford DC Line between Queens Park and Harrow & Wealdstone is used by London Overground trains designed for 750 V third rail and Bakerloo Line trains designed for 630 V third and fourth rail. As a compromise the nominal line voltage is 650 V, and the centre rail is bonded to the running rails. There are no special provisions needed at Queens Park where the two dissimilar systems meet, merely a gap longer than one coach of a Bakerloo Line train at the entry to and exit from the Bakerloo Line section, which operates with nominally -210V on th fourth rail and +420V on the third rail. There is no bridging of these incompatible systems as trains pass from one to the other, because like all UK electric trains intended to run extensively in tunnels, there is no continuity of traction power circuits between vehicles in the train. There are currently plans to run the Bakerloo Line trains to Watford Junction, as they have much greater passenger capacity then the shorter London Overground trains, in which case the fourth rail, currently retained in most places to assist the conductivity of the running rails but not mechanically in good order, will have to be restored to good working order.


 * The North London Line between Richmond and Gunnersbury is used by London Overground trains designed for 750 V third rail and District Line trains designed for 630 V third and fourth rail. As a compromise the nominal line voltage is 660 V, and the centre rail is bonded to the running rails. A similar arrangement appleies on the District Line between Putney Bridge and Wimbledon, where District Line tracks also used by South West Trains, although the latter are not normally in passenger service.


 * Northern City Line

The Northern City Line connects the East Coast Main Line to Moorgate. It was isolated by the abandonment of the 1930s "New Works" programme (and the development of the Metropolitan Green Belt). Tube services were truncated at its northern end by the new Victoria Line in 1964, at Drayton Park. The remainder was handed over to BR in 1975 in conjunction with the suburban electrification of the East Coast Main Line. The line uses 25 kV AC overhead and third rail DC electrification, with the switchover at the platform at Drayton Park.

750 V DC, Third rail (Bottom Contact)

 * Docklands Light Railway
 * This system uses bottom-contact third rail. The third rail is composite, with an aluminium body and a steel contact surface.  The benefit of this is a low-resistance, high current capacity rail that has a durable steel surface for current collection.

750 V DC, Overhead

 * Manchester Metrolink
 * Sheffield Supertram
 * Croydon Tramlink
 * Nottingham express transit
 * Midland Metro

1,500 V DC, Overhead



 * Tyne and Wear Metro
 * When 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, this system was used. Styled as "Light Rail" it is, in practice, normal heavy rail and shares the Durham Coast Line with the national rail network (unlike the other tram systems in the UK, which operate alongside on separate rights of way).

25 kV, 50 Hz AC, Overhead


The majority of this line was originally electrified at 6,250 V. It was converted to 25 kV in the early 1960s.
 * London, Tilbury and Southend (LTS)


 * Great Eastern Main Line (GEML)


 * Converted from 1,500 V DC (see 1,500 V DC section "Shenfield Metro")
 * Converted from 6,250 V/1,500 V DC
 * Romford to Upminster Line
 * Shenfield to Southend Line
 * Crouch Valley Line
 * Braintree Branch Line
 * Colchester to Clacton Line
 * Mayflower Line


 * West Anglia / Fen Line
 * This covers the lines from London Liverpool Street (Bethnal Green Jn) to Chingford, Enfield Town, Hertford East, and Cambridge. The line was first electrified in the 1960s when the lines to Chingford, Enfield Town and Cheshunt were electrified at 6,250 V. The line from Cheshunt to Bishop's Stortford and Hertford East was electrified at 25 kV. The Lea Valley line between Coppermill Junction and Cheshunt was electrified at 25 kV in 1969. All the 6,250 V areas were converted to 25 kV in 1983. In 1987, electrification was extended from Bishop's Stortford to Cambridge using 25 kV. In 1990, the line to Stansted Airport opened and, in 1992, electrification was further extended from Cambridge to King's Lynn along the Fen Line.


 * East Coast Main Line (ECML)
 * Electrified in two parts, the first between 1975 and 1978 and the second between 1984 and 1991.
 * The line between London (Kings Cross) and Royston was electrified between 1976 and 1978 as part of the Great Northern Suburban Electrification Project. This included the Hertford Loop Line.
 * In 1984, authority was given to electrify to Edinburgh and Leeds. The section between Hitchin and Peterborough was completed in 1987 and Doncaster and York were reached in 1989. By 1990, electrification had reached Newcastle and, in 1991, the final section to Edinburgh was completed.
 * In order to keep the construction teams busy, two additional schemes were authorised that extended electrification to Carstairs and to North Berwick (North Berwick Line).
 * At the peak of electrification works in the late 1980s, it claimed to be the "longest construction site in the world", at over 400 km.


 * Midland Main Line (MML)
 * Electrified between London (St Pancras) and Bedford in 1983. The branch from Dock Junction to Moorgate was also electrified.
 * See also Thameslink


 * West Coast Main Line (WCML)
 * Electrified from the late 1950s to the mid 1960s under the BR 1955 Modernisation Plan as far as Crewe (and branches), it was extended to Scotland in 1974.
 * Northampton - see Northampton Loop Line
 * Birmingham (New Street) - see Rugby-Birmingham-Stafford Line
 * Liverpool (Lime Street)
 * Manchester (Piccadilly) - see Stafford to Manchester Line and Crewe to Manchester Line.
 * Glasgow (Central) - in 1974 from Weaver Junction.
 * The "Abbey Flyer" (St Albans Branch Line) was electrified 1987-88 by Network SouthEast
 * Edinburgh (Waverley) in 1989 (from Carstairs Junction in conjunction with ECML electrification).
 * In 2003 Crewe to Kidsgrove section of the Crewe to Derby Line was electrified as a diversionary route for the WCML.
 * Since 1999 the line has been modernised and the overhead line equipment has undergone a programme of refurbishment and renewal as part of works to increase train speeds from 110 mph to 125 mph.


 * Edinburgh
 * 1991 the ECML to Edinburgh was electrified. A few local routes were electrified, but the most of local services were not.
 * Edinburgh Crossrail - only Edinburgh Waverley to Newcraighall. Currently the service is by DMUs, pending reopening of part of the Waverley Line
 * North Berwick Line - Edinburgh Waverley to North Berwick, with some extensions to Edinburgh Haymarket.
 * Glasgow to Edinburgh via Carstairs Line - some North Berwick Line trains continue to Glasgow Central. Intercity trains from the ECML continue to Glasgow Central.
 * – see also: Transport in Edinburgh

The route from Edinburgh to Glasgow via Bathgate is currently (2010) being reinstated between Bathgate and Airdrie, and electrified throughout. This is due to open to passengers on 11 December 2010 and is mainly aimed at commuters and similar local use, as the route and number of station stops precludes high overall speeds.
 * Central Scotland

Approval has also been given by the Scottish Parliament for electrification of the main inter-city route between Edinburgh and Glasgow Queen Street (High level station, not currently electrified), via Falkirk. This project will also encompass some infill electrification in the Glasgow area, and Greenhill Junction to Stirling, Dunblane and, recently re-opened, Alloa, which mainly carry commuter services, however it will make possible electric haulage from London via the ECML as far as Stirling or even Dunblane, which may influence the operation of London to Inverness services, currently operated by an HST.

Suburban electrification was started in the 1960s in the wake of the BR 1955 Modernisation Plan. Electrification was piecemeal over the preceding year and is still incomplete, with several suburban, rural and inter city lines still unelectrified. See also: SPT and Transport in Glasgow.
 * Glasgow Suburban


 * The Glasgow Suburban railway network can be split into three main areas;


 * North Clyde
 * Also known as "Glasgow North Electric Suburban Line", this was one of the first lines in Glasgow to be electrified, in 1960. Helensburgh Central, Balloch and Milngavie to Glasgow Queen Street (Low Level) and to Springburn and Drumgelloch.


 * South Clyde
 * Cathcart Circle Line - ( Glasgow Central to Newton and Neilston) was electrified on 22nd May 1962
 * Inverclyde Line - (Glasgow Central to Gourock and Wemyss Bay), electrified in 1967.


 * Ayrshire Coast Line - Glasgow Central to Ayr, Largs and Ardrossan Harbour, electrified in 1986/87.


 * Paisley Canal Line - electrified only as far as Corkerhill (from Glasgow Central)


 * West Coast Main Line


 * Argyle Line - Dalmuir and Milngavie via Glasgow Central (Low Level) to Hamilton Circle, Larkhall, Lanark and Carstairs (via a variety of lines via Hamilton, Motherwell or Holytown). There is also a peak service to Coatbridge Central


 * Glasgow to Edinburgh via Carstairs Line - some North Berwick Line trains continue to Glasgow Central. GNER intercity trains (from the ECML) continue to Glasgow Central.


 * Motherwell to Cumbernauld Line - the Motherwell to Coatbridge section is electrified, but the Coatbridge to Cumbernauld section is not.


 * Shotts Line - the central section (Holytown Junction to Kirknewton) is not electrified but both ends are electrified, as they are shared with the WCML, Argyle Line and ECML.


 * Whifflet Line - the section that follows the WCML (Glasgow Central to Rutherglen) is electrified, the rest of the line to Whifflet is not.


 * Leeds area
 * The main line to Leeds from London (via Wakefield Westgate) was electrified in 1989. In 1994, a project to electrify some of the local lines around Leeds was given authority to proceed. The project was called the "Leeds North West Electrification", and covered lines to Bradford (Forster Square), Skipton (Airedale Line) and Ilkley (Wharfedale Line).


 * Manchester area -
 * Manchester to Glossop / Hadfield (converted from the truncated 1500 V DC Manchester-Sheffield-Wath electric railway),
 * Manchester, South Junction and Altrincham Railway (part was converted to Manchester Metrolink)
 * Styal Line (primarily operated by diesel multiple units)
 * Stafford to Manchester Line - branch of WCML, electrifed in the wake of the BR 1955 Modernisation Plan.
 * Crewe to Manchester Line - branch of WCML, electrifed in the wake of the 1955 Modernisation Plan.
 * Liverpool to Manchester Line - to be electrified as part of plans announced by the British government in July 2009


 * West Midlands area
 * A few lines out of New Street mainly related to the West Coast Main Line.
 * Trent Valley Line - WCML, 1964.
 * Rugby-Birmingham-Stafford Line - WCML, 1966.
 * Cross-City Line - 1993.
 * Walsall Line - electrified from New Street to Walsall.


 * Great Western Main Line (GWML)
 * Electrified in 1994 between London Paddington and Heathrow Airport, a joint venture between British Rail and the British Airports Authority.
 * As part of the works for Crossrail, the electrified section will be extended as far as Maidenhead. The British government also announced in July 2009 that the remaining sections of line from Maidenhead to Bristol and Swansea would be electrified.
 * See Heathrow Express and Heathrow Connect
 * See also Electrification of GWML


 * London Crossrail

25-0-25 kV, 50 Hz AC, Overhead, Autotransformer

 * High Speed 1
 * This is the first time that an auto-transformer system has been used in the UK.


 * West Coast Main Line (WCML)
 * This is currently in use between Ashton (north of Milton Keynes) and Hillmorton (south of Rugby), but planned to be extended along most of the route between London and Glasgow.