Northern line

The Northern line is a deep-level London Underground line. It is coloured black on the Tube map. The line carries 206,734,000 passengers per year. This is the highest on the London Underground system but, exceptionally, the line does have two branches through the centre of London. For most of its length it is built as a deep-level tube line. Despite its name, the Northern line does not serve the northernmost stations on the Underground network, although it does serve the southernmost station (Morden) and serves sixteen of the Underground system's 29 stations south of the River Thames. There are 50 stations on the Northern line, of which 36 are underground.

The line has a complicated history and the current complex arrangement of two northern branches, two central branches and the southern branch reflects its genesis as three separate railway companies that were brought together and combined in the 1920s and 1930s. An extension in the 1920s used a route originally planned by a fourth company. Abandoned plans dating from the 1920s, to extend the line further southwards, and then northwards in the 1930s, would have incorporated parts of the routes of two further companies. From the 1930s to the 1970s, the tracks of a seventh company were also managed as a branch of the Northern line.

Formation

 * See City and South London Railway and Charing Cross, Euston and Hampstead Railway for detailed histories of these companies

The core of the Northern line evolved from two railway companies: the City & South London Railway (C&SLR) and the Charing Cross, Euston & Hampstead Railway (CCE&HR).

The C&SLR, London's first deep-level tube railway, was built under the supervision of James Henry Greathead, who had been responsible, with Peter W. Barlow, for the Tower Subway. It was the first of the Underground's lines to be constructed by boring deep below the surface and the first to be operated by electric traction. The railway opened in November 1890 from Stockwell to a now-disused station at King William Street. This was inconveniently placed and unable to cope with the company's traffic so, in 1900, a new route to Moorgate via Bank was opened. By 1907 the C&SLR had been further extended at both ends to run from Clapham Common to Euston.

The CCE&HR (commonly known as the "Hampstead Tube") was opened in 1907 and ran from Charing Cross (known for many years as Strand) via Euston and Camden Town (where there was a junction) to Golders Green and Highgate (now known as Archway). It was extended south by one stop to Embankment in 1914 to form an interchange with the Bakerloo and District lines. In 1913, the Underground Electric Railways Company of London (UERL), owner of the CCE&HR, took over the C&SLR, although they remained separate companies.

Integration
During the early 1920s, a series of works was carried out to connect the C&SLR and CCE&HR tunnels to enable an integrated service to be operated. The first of these new tunnels, between the C&SLR's Euston station and the CCE&HR's station at Camden Town, had originally been planned in 1912, but had been delayed by World War I. The second connection linked the CCE&HR's Embankment and C&SLR's Kennington stations and provided a new intermediate station at Waterloo to connect to the main line station there and the Bakerloo line. The smaller-diameter tunnels of the C&SLR were expanded to match the standard diameter of the CCE&HR and the other deep tube lines.

Extensions
In conjunction with the works to integrate the two lines, two major extensions were undertaken: northwards to Edgware in Middlesex (now in the London Borough of Barnet) and southwards to Morden in Surrey (then in the Merton and Morden Urban District, but now in the London Borough of Merton).

Edgware Extension
The Edgware extension utilised plans dating back to 1901 for the Edgware and Hampstead Railway (E&HR) which the UERL had taken over in 1912. It extended the CCE&HR line from its terminus at Golders Green to Edgware in two stages: to Hendon Central in 1923 and to Edgware in 1924. The line crossed undeveloped open countryside and was on the surface, apart from a short tunnel north of Hendon Central. Five new stations were constructed to pavilion-style designs by Stanley Heaps, stimulating the rapid northward expansion of suburban developments in the following years.

Morden Extension
The engineering of the Morden extension of the C&SLR from Clapham Common to Morden was more demanding, running in tunnel to a point just north of Morden station, which was constructed in a cutting. The extension was initially planned to continue to Sutton over part of the route for the unbuilt Wimbledon and Sutton Railway, in which the UERL held a stake, but agreements were made with the Southern Railway to end the extension at Morden. The extension opened in 1926 with seven new stations, all designed by Charles Holden in a modern style. With the exception of Morden and Clapham South, where more land was available, the new stations were built on confined corner sites at main road junctions in already developed areas. Holden made good use of this limited space and designed impressive buildings. The street-level structures are of white Portland stone with tall double-height ticket halls, with the famous London Underground roundel made up in coloured glass panels in large glazed screens. The stone columns framing the glass screens are surmounted by a capital formed as a three-dimensional version of the roundel. The large expanses of glass ensure that the ticket halls are bright and, lit from within at night, welcoming. The first and last new stations on the extension, Clapham South and Morden, include a parade of shops and were designed with structures capable of being built above (like many of the earlier Central London stations). Clapham South was extended upwards soon after its construction with a block of apartments; Morden was extended upwards in the 1960s with a block of offices. All the stations on the extension, except Morden itself, are Grade II listed buildings.

Naming
The resulting line became known as the Morden–Edgware line, although a number of alternative names were also mooted in the fashion of the contraction of Baker Street & Waterloo Railway to "Bakerloo", such as "Edgmor", "Mordenware", "Medgway" and "Edgmorden". It was eventually named the Northern line in August 1937, reflecting the planned addition of the Northern Heights lines.

Great Northern & City Railway
After the UERL and the Metropolitan Railway (MR) were brought under public control in the form of the London Passenger Transport Board (LPTB) in 1933, the MR's subsidiary, the Great Northern & City Railway, which ran from Moorgate to Finsbury Park, became part of the Underground as the Northern City Line. In preparation for the Northern Heights Plan, it was operated as part of the Northern line, although it was never connected to it.

The Northern Heights plan

 * See Edgware, Highgate and London Railway for a detailed history of that company

In June 1935, the LPTB announced the New Works Programme, an ambitious plan to expand the Underground network which included the integration of a complex of existing London and North Eastern Railway (LNER) lines north of Highgate through the Northern Heights. These lines, built in the 1860s and 1870s by the Edgware, Highgate and London Railway (EH&LR) and its successors, ran from Finsbury Park to Edgware via Highgate, with branches to Alexandra Palace and High Barnet. The line taken over would be extended beyond Edgware to Brockley Hill, Elstree South and Bushey Heath with a new depot at Aldenham. The extension's route was that planned for the unbuilt Watford and Edgware Railway (W&ER), using rights obtained from the earlier purchase of the W&ER (which had long-intended an extension of the EH&LR Edgware route towards Watford). This also provided the potential for further extension in the future if required; indeed, Bushey's town planners reserved space in Bushey village for a future station and Bushey Heath station's design was revised several times to ensure this option would remain available in the future.

The project involved electrification of the surface lines (operated by steam trains at the time), the doubling of the original single-line section between Finchley Central and the proposed junction with the Edgware branch of the Northern line, and the construction of three new linking sections of track: a connection between Northern City Line and Finsbury Park station on the surface; an extension from Archway to the LNER line near East Finchley via new deep-level platforms below Highgate station; and a short diversion from just before the LNER's Edgware station to the Underground's station of the same name.

Intended service levels
The peak hour service levels would have seen 21 trains an hour each way on the Barnet branch north of Camden Town, 14 via the Charing Cross branch and seven via the Bank branch. 14 would have continued on beyond Finchley Central, seven each on the High Barnet and Edgware branches. An additional seven trains an hour would have served the Barnet branch, but continued via Highgate High-Level and Finsbury Park to Moorgate, a slightly shorter route to the City. It does not seem to have been intended to run through trains to the ex-Northern City branch from Edgware via Finchley Central. Seven trains an hour would have served the Alexandra Palace branch, to/from Moorgate via Highgate High-level. In addition to the 14 through trains described, the ex-Northern City branch would have had 14 4-car shuttle trains an hour.

Progress of works
Work began in the late 1930s, and was in progress on all fronts by the outbreak of World War II. The tunneling northwards from the original Highgate station (now Archway) had been completed and the service to the rebuilt surface station at East Finchley started on 3 July 1939, but without the opening of the intermediate (new) Highgate Station, at the site of the LNER's station of the same name. Further progress was disrupted by the start of the war, though enough had been made to complete the electrification of the High Barnet branch onwards from East Finchley over which tube services started on 14 April 1940; the new (deep-level) Highgate station finally opened on 19 January 1941. The single track LNER line to Edgware was electrified as far as Mill Hill East, including the Dollis Brook Viaduct, opening as a tube service on 18 May 1941 to serve the barracks there, thus forming the Northern line as it is today. The new depot at Aldenham had already been built and was used to build Halifax bombers. Work on the other elements of the plan was suspended late in 1939.

Preparatory work including viaducts and a tunnel had been started but not completed on the Bushey extension pre-war. After the war, however, the area beyond Edgware was made part of the Metropolitan Green Belt largely preventing the anticipated residential development in the area and the potential demand for services from Bushey Heath thus vanished. Available funds were directed towards completing the eastern extension of the Central line instead, and the Northern Heights plan was dropped on 9 February 1954. Aldenham depot was converted into an overhaul facility for buses. The implemented service from High Barnet branch gave good access both to the West End and the City. This appears to have undermined traffic on the Alexandra Palace branch still run with steam haulage to Kings Cross via Finsbury Park, as Highgate (low-level) was but a short bus ride away and car traffic was much lighter than it would become later. Consequently, the line from Finsbury Park to Muswell Hill and Alexandra Palace via the surface platforms at Highgate was closed altogether to passenger traffic in 1954. This contrasts with the decision to electrify the Epping-Ongar branch of the Central line, another remnant of the New Works programme, run as a tube train shuttle from 1957. A local pressure group, the Muswell Hill Metro Group, campaigns to reopen this route as a light rail service. So far there is no sign of movement on this issue: the route, now the Parkland Walk, is highly valued by walkers and cyclists and suggestions in the 1990s that it could, in part, become a road were met with fierce opposition. Another pressure group has proposed using the track bed further north, as part of the North and West London Light Railway. The connection between Drayton Park and the surface platforms at Finsbury Park was eventually opened in 1976, the Northern City Line becoming part of British Rail.

The rural railway heritage of the High Barnet branch beyond Highgate can be seen in the design of many of the stations.

Rolling stock
All Northern line trains consist of London Underground 1995 Stock and are in the distinctive Underground livery of red, white and blue. In common with the other deep-level lines, the trains are the smaller of the two sizes used on Underground. 1995 stock sports automated announcements and quick-close doors. Should the proposed split of the line take place (estimated for 2018), then 19 new additional trains will be delivered alongside the existing fleet.

Tunnels
Although other London Underground lines operate fully underground, the Northern line is unusual in that it is a deep-level tube line that serves the outer suburbs yet there are only a few stations above ground. This is partly because its southern extension into the outer suburbs was not done by taking over an existing surface line as was generally the case with routes like the Central, Jubilee and Piccadilly lines. Apart from the core central underground tunnels, part of the section between Hendon and Colindale is also underground. As bicycles are not allowed in tunnel sections (even if no station is in that section) as they would hinder evacuation, they are limited to High Barnet - East Finchley, the Mill Hill East branch, Edgware - Colindale and Hendon - Golders Green. There are also time-based restrictions.

From the time of construction until the completion of the Channel Tunnel, the tunnel from Morden to East Finchley via Bank was the longest in the world at 17 miles 528 yards (27.841 km).

Depots
The Northern line is serviced by two depots. The main one is at Golders Green and is located adjacent to Golders Green tube station, while the second, at Morden, is south of Morden tube station and is the larger of the two. There are also sidings at Highgate, Edgware and High Barnet that are used to hold trains overnight.

Closed Stations

 * King William Street (closed 1900)
 * City Road (closed 1922)
 * South Kentish Town (closed 1924)
 * North End (never opened - work stopped 1906)

Resited Stations

 * Stockwell - new platforms resited immediately to the south of its predecessor with the 1922-1924 upgrade of the line.
 * Euston - Northbound City branch platform resited on new alignment, with previous island platform converted to a single platform
 * Angel - old island platform converted into a single platform, and a new alignment opened in 1992, along with a new entrance.
 * London Bridge - the northbound tunnel and platform converted into a concourse, and a new northbound tunnel and platform built in the late 1990s to increase the platform and circulation areas in preparation for the opening of the Jubilee line.

Abandoned Plans
Northern Heights stations not transferred from LNER
 * Highgate - High-level only
 * Stroud Green
 * Crouch End
 * Cranley Gardens
 * Muswell Hill
 * Alexandra Palace
 * Mill Hill (The Hale)

Bushey Extension stations not constructed
 * Brockley Hill
 * Elstree South
 * Bushey Heath

Recent developments
In 1975, the Northern City Line, known by that time as the Highbury branch, became part of British Rail; it is now served by First Capital Connect.

In the 1980s and 1990s the line was nicknamed the "Misery Line", but its reputation has improved somewhat since the introduction of the 1995 stock.

In 2003, a train derailed at Camden Town. Although no one was hurt, points and signals were damaged, and the junctions there were not used while repairs were under way: trains coming from Edgware worked the Bank branch only, and trains from High Barnet and Mill Hill East worked the Charing Cross branch only. This situation was resolved when the junctions reopened, after much repair work and safety analysis and testing, on 7 March 2004.

A joint report by the Underground and its maintenance contractor Tube Lines concluded that poor track geometry was the main cause, and that, because of this, extra friction arising out of striations (scratches) on a newly installed set of points had allowed the leading wheel of the last carriage to climb the rail and so derail. The track geometry at the derailment site is a very tight bend and tight tunnel bore, which precludes the normal solution for this sort of geometry of canting the track by raising the height of one rail relative to the other.

On 7 July 2005 a defective train on the Northern line (causing its subsequent suspension) saved a Northern line train from being blown up as part of a massive terrorist attack on the London Underground and bus systems. Three trains on the Circle and Piccadilly lines were not so lucky. The Northern line bomber instead boarded a bus, which he later blew up.

On 13 October 2005 the entire Northern line service was suspended due to maintenance problems with the emergency braking system on the trains. A series of rail replacement buses was used to connect outlying stations with other Underground lines. A reduced service was reintroduced on 17 October 2005, and full service was restored on 18 October.

In October 2006, off-peak service between Mill Hill East and Finchley Central was cut back to a shuttle, except for a few weekend through trains.

From June 2006, the service between East Finchley and Camden Town was suspended for two non-consecutive weekends every month, with service on the Edgware branch suspended for the other two weeks. This was part of Tube Lines's redevelopment of some Edgware and High Barnet Branch stations, including replacement of track, signals, as well as station maintenance. This included refurbishment of all High Barnet branch stations running from West Finchley tube station down to Camden Town tube station.

In August 2010, a defective maintenance train caused disruption on the Charing Cross branch, after it travelled four miles in 13 minutes without a driver. The train was being towed to the depot after becoming faulty. At Archway tube station, the defective train became detached and ran driverless until coming to at stop at an incline near Warren Street tube station. This caused morning rush-hour services to be effectively suspended on this branch. All passenger trains were diverted via the Bank branch, with several not stopping at stations until they were safely on the Bank branch.

Future
The Northern line was scheduled to switch to automatic train operation in 2012, using the same SelTrac system which was due to be commissioned on the Jubilee line in 2009 and has been in use for a number of years on the Docklands Light Railway. Work was originally planned to follow on from the Jubilee line in order to benefit from the experience of installing it there the but that project is not now expected to be complete until spring 2011. Originally work on the Northern line was intended to be completed by the contractually stipulated date which was before the 2012 Olympics. With the work now being taken in-house and no contractual deadlines to meet a more realistic timetable suggests that it will be complete in 2014.

TfL's Transport 2025 - Transport vision for a growing world confirms its long-term ambition to split the Northern line into two segregated routes. Running trains between all combinations of branches and the two central sections, as is currently done, means only 20-22 trains an hour can run on each of the central sections, because merging trains have to wait for each other at the junctions. Completely segregating the routes will allow 32 trains an hour on all parts of the system. However, Camden Town tube station will need to be rebuilt before this can be implemented as the current station would not be able to cope with the increased number of passengers changing trains there. London Underground Limited (LUL) had, however, had problems gaining planning permission for the redevelopment plans. All plans for a revised scheme for Camden Town station have been delayed by budgetary cuts.

Because the full split is not possible without a rebuilt Camden Town station and the need to increase capacity remains, the current plan is to achieve a partial split by terminating all Charing Cross branch trains at Kennington during normal service. This would eliminate the need to co-ordinate train paths southbound when they merge at Kennington and would enable the Morden-Bank branch to operate at the maximum capacity that the new signalling system will allow. This will not happen until the line has been resignalled as it is only then that the full benefits of this plan can be realised.

In June 2008, Treasury Holdings, owners of Battersea Power Station, announced proposals for an extension of the Northern line from Kennington to a station in Battersea to serve a redeveloped power station site. The plan has been approved by the London Borough of Wandsworth and the extension could be opened by 2015 as part of a planned redevelopment of the Battersea Power Station. In October 2009, the proposal received a boost when Mayor of London Boris Johnson announced that developers of the area would be exempt from the Crossrail levy and instead required to pay towards the proposed Northern line extension. In May 2010 the company proposing the route revealed four options for the route. Option 1 is for a non-stop from to Battersea. Option 2 is for a station in the middle of Nine Elms then a station at Battersea. Option 3 is for two new platforms at Vauxhall and then to Battersea and option 4 is for a station near the U.S. Embassy and then to Battersea.

In the long term, a full operational split of the line into two distinct non-overlapping routes could lead to one or both being renamed and given a different colour on the tube map. If the Battersea extension does not get built there are opportunities to extend from Kennington to other places in south-east London, such as Camberwell, in line with the Mayor's transport policy to provide greater tube coverage in that area.

Maps

 * High Barnet - 51.65056°N, -0.19417°W
 * Totteridge and Whetstone - 51.63056°N, -0.17917°W
 * Woodside Park - 51.61806°N, -0.18556°W
 * West Finchley - 51.60944°N, -0.18833°W
 * Mill Hill East - 51.60833°N, -0.21028°W
 * Finchley Central - 51.60111°N, -0.1925°W
 * East Finchley - 51.58722°N, -0.165°W
 * Highgate - 51.57778°N, -0.14583°W
 * Archway - 51.56556°N, -0.135°W
 * Tufnell Park - 51.55667°N, -0.13806°W
 * Kentish Townq - 51.55028°N, -0.14056°W
 * Edgware - 51.61389°N, -0.275°W
 * Burnt Oak - 51.60278°N, -0.26389°W
 * Colindale - 51.59556°N, -0.25°W
 * Hendon Central - 51.58306°N, -0.22611°W
 * Brent Cross - 51.57667°N, -0.21361°W
 * Golders Green - 51.57194°N, -0.19389°W
 * Hampstead - 51.55694°N, -0.17833°W
 * Belsize Park - 51.55028°N, -0.16444°W
 * Chalk Farm - 51.54417°N, -0.15333°W
 * Camden Town - 51.53944°N, -0.14278°W
 * Mornington Crescent - 51.53444°N, -0.13861°W
 * Euston - 51.52833°N, -0.13306°W
 * Warren Street - 51.52472°N, -0.13833°W
 * Goodge Street - 51.52083°N, -0.13444°W
 * Tottenham Court Road - 51.51611°N, -0.13083°W


 * Leicester Square - 51.51139°N, -0.12806°W
 * Charing Cross - 51.50806°N, -0.12472°W
 * Embankment - 51.50694°N, -0.12194°W
 * Waterloo - 51.5025°N, -0.11306°W
 * King's Cross St. Pancras - 51.53028°N, -0.12417°W
 * Angel - 51.53194°N, -0.10611°W
 * Old Street - 51.52583°N, -0.08722°W
 * Moorgate - 51.51861°N, -0.08861°W
 * Bank-Monument - 51.51306°N, -0.08806°W
 * London Bridge - 51.505°N, -0.08611°W
 * Borough - 51.50111°N, -0.09306°W
 * Elephant & Castle - 51.49444°N, -0.09972°W
 * Kennington - 51.48861°N, -0.10556°W
 * Oval - 51.48194°N, -0.1125°W
 * Stockwell - 51.4725°N, -0.12222°W
 * Clapham North - 51.465°N, -0.13°W
 * Clapham Common - 51.46167°N, -0.13861°W
 * Clapham South - 51.45278°N, -0.1475°W
 * Balham - 51.4425°N, -0.15194°W
 * Tooting Bec - 51.43583°N, -0.15972°W
 * Tooting Broadway - 51.42778°N, -0.16833°W
 * Colliers Wood - 51.41833°N, -0.17833°W
 * South Wimbledon - 51.41556°N, -0.19194°W
 * Morden - 51.40222°N, -0.195°W
 * Golders Green depot - 51.57278°N, -0.19306°W
 * Morden depot - 51.3975°N, -0.19694°W