Editing Metropolitan line (section)

== Route ==
{{wide image|Metropolitan Line & London map.svg|700px|The route of the Metropolitan line through the [[London Boroughs|Greater London Boroughs]] and the [[English Counties]] of [[Hertfordshire]] and [[Buckinghamshire]]. More details of the route between Baker Street and Aldgate are shown on [[Circle line (London Underground)#Map|Circle line: Map]]|center}}
{{Metropolitan Main Line}}
The Metropolitan line is {{convert|67|km|mi|1|order=flip}} long and serves 34 stations.<ref name="Key Facts">{{cite web|title=Key facts |work=Transport for London |url=http://www.tfl.gov.uk/corporate/modesoftransport/londonunderground/1608.aspx |access-date=22 November 2012 |url-status=dead |archive-url=https://web.archive.org/web/20070529041317/http://www.tfl.gov.uk/corporate/modesoftransport/londonunderground/1608.aspx |archive-date=29 May 2007 }}</ref> It is electrified with a four-rail DC system: a central conductor rail is energised at –250&nbsp;V and a rail outside the running rail at +500&nbsp;V, giving a potential difference of 750&nbsp;V, except for the section from Uxbridge to Finchley Road (via Harrow-on-the-Hill) which is energised at&nbsp;–210&nbsp;V and +420&nbsp;V respectively (630&nbsp;V potential difference) to maintain compatibility with [[London Underground 1973 Stock|1973 Stock]] and [[London Underground 1996 Stock|1996 Stock]] that runs in those areas.<ref>{{Cite web|url=https://www.squarewheels.org.uk/rly/stock/SsubsurfaceStock/|title=SQUAREWHEELS.org.uk – S stock|last=Richard Griffin|website=www.squarewheels.org.uk|language=en|date=3 September 2019|access-date=11 May 2020}}</ref><ref name="Martin2012">{{cite book |author= Martin, Andrew |title= Underground, Overground: A Passenger's History of the Tube |url= https://books.google.com/books?id=vh3n5WD_YqsC&pg=PT137 |access-date=7 December 2012 |year=2012 |publisher= Profile Books |isbn=978-1-84765-807-4 |location=London |pages=137–138}}</ref> The first {{convert|6|mi}} from [[Aldgate tube station|Aldgate]] are below ground,<ref name="Line Facts">{{cite web |url= http://www.tfl.gov.uk/corporate/modesoftransport/londonunderground/keyfacts/13173.aspx |title=Metropolitan line facts |publisher=Transport for London |access-date=23 November 2012}}</ref> shared with the [[Circle line (London Underground)|Circle]] and Hammersmith & City lines to Baker Street, where the line diverges, remaining in tunnel until [[Finchley Road tube station|Finchley Road]].<ref name="map">{{cite web|url=http://cartometro.com/cartes/metro-london/|title=Detailed London Transport Map|access-date=23 November 2012|work=cartometro.com}}</ref> Metropolitan line trains essentially skip two stops between Baker Street and Finchley Road, with the Jubilee line serving the intermediate stations on an adjacent parallel line. The Jubilee line then joins the Metropolitan line in the same right-of-way at Finchley Road. Metropolitan line trains then run express from Finchley Road to [[Wembley Park tube station|Wembley Park]], with the Jubilee line serving the intermediate stations. Metropolitan line platforms at {{lus|Willesden Green}} and {{lus|Neasden}} remain for emergency use.<ref>{{cite web |last1=Marius |first1=Callum |title=Why the Metropolitan line has 2 extra secret stations you may not know about |url=https://www.mylondon.news/news/north-london-news/london-underground-metropolitan-line-2-21320342 |website=MyLondon |access-date=4 November 2022 |language=en |date=16 August 2021}}</ref> At Wembley Park the Jubilee line diverges to the Stanmore branch at a grade-separated junction. From just after Finchley Road, these four tracks run parallel with the [[Network Rail]] [[Chiltern Main Line]] from [[Marylebone station|Marylebone]].<ref name="map" />

Between Wembley Park and [[Harrow-on-the-Hill station|Harrow-on-the-Hill]], the Metropolitan is four-track, with fast and slow lines paired by direction, paralleling the two-track un-electrified [[London–Aylesbury line]]. The slow lines are between the fast lines, and the two intermediate stations have island platforms.<ref name="map" /> Harrow-on-the-Hill has platforms on all six lines.<ref name="map" /> The  central slow lines diverge here at a [[grade separation|grade-separated]] junction to become the {{convert|7.5|mi}} Uxbridge branch. After [[West Harrow tube station|West Harrow]], at [[Rayners Lane tube station|Rayners Lane]] the line is joined by the [[Piccadilly line]], which shares the tracks to Uxbridge; a [[turnback]] siding allows some Piccadilly line services to terminate at Rayners Lane.<ref name="map" />{{sfn|Horne|2003|p=x}}

On the main line between Harrow-on-the-Hill and [[Moor Park tube station|Moor Park]], the line is four-track, paired by use. The western fast tracks are shared with Aylesbury line services from Marylebone; the eastern slow tracks have platforms at the intermediate stations.

North of Moor Park, the Watford branch diverges from the slow lines.<ref name="map" /> This double-track branch has stations at [[Croxley tube station|Croxley]] and [[Watford tube station|Watford]].<ref name="map" /><ref name="Croxley plans" /> The Watford branch has a [[Wye (rail)|triangle junction]] with the main line, with a north-facing curve between {{lus|Croxley}} and {{lus|Rickmansworth}}. This route, Watford North Curve, is used daily for a few services and empty stock movements.<ref>{{cite news |last1=Louis |first1=Nathan |title=The 'secret' Met line track near Watford known as 'North Curve' |url= https://www.watfordobserver.co.uk/news/19499343.secret-met-line-track-near-watford-known-north-curve/ |website=Watford Observer |date=8 August 2021 |access-date=15 September 2021}}</ref>

From the Watford triangle to [[Amersham station|Amersham]], the line has two tracks. At [[Chalfont & Latimer station|Chalfont & Latimer]], the {{convert|3.89|mi}} [[single track (rail)|single-track]] [[Chesham branch]] diverges, running parallel to the main line for a distance.<ref name="Key Facts" /><ref name="map" /> The Metropolitan line ends at Amersham, where there are turnback sidings just beyond the platforms. The route continues to [[Aylesbury railway station|Aylesbury]] with Chiltern Railways trains only.<ref name="AmCh">{{cite web | url=http://www.tfl.gov.uk/assets/downloads/amersham-chesham-tube-guide.pdf | title=Amersham/Chesham tube guide | work=Transport for London | access-date=9 December 2013}}</ref>

The fast (non-stopping) lines between Wembley Park and Harrow on the Hill are signalled with LUL signalling, but using four-aspect Network Rail signal heads.<ref name="BRS">{{cite book |title= British Railway Signalling |author1=Kichenside, G.M. |author2= Williams, Alan |page=72}}</ref> The upper two lights are a two-aspect stop signal displaying either a green or red aspect, the lower two lights a repeater signal for the next stop signal ahead showing a green or yellow aspect, or no aspect when the stop signal shows a red aspect. Thus they are effectively four-light three-aspect signals with green/red/green/yellow lights from the top, danger being a single red light, caution the top green light over a yellow light, and clear two green lights.<ref name="BRS" />

The Metropolitan line's suburban rail character opposed to other London Underground lines is also shown by the long distances between stops. Eight of the top 10 furthest apart stations on the Underground are on the Metropolitan line. The section between Chalfont & Latimer and Chesham is the longest at {{convert|3.9|mi}},<ref>{{cite web|url=https://tfl.gov.uk/corporate/about-tfl/what-we-do/london-underground/facts-and-figures |title=Facts & figures |publisher=Transport for London |website=tfl.gov.uk |access-date=14 July 2017}}</ref> whilst the Finchley Road to Wembley Park section is the second longest, and Rickmansworth to Chorleywood the fourth longest overall.