View source for Junction (rail)

{{broader|Junction (traffic)}}{{Short description|Train track interchange}}
{{more references|date=October 2012}}
[[File:CTA loop junction.jpg|thumb|[[Chicago Transit Authority]] [[Signalling control|signal tower]] 18 guides elevated [[Chicago 'L']] north and southbound [[Purple Line (Chicago Transit Authority)|Purple]] and [[Brown Line (Chicago Transit Authority)|Brown]] lines intersecting with east and westbound [[Pink Line (Chicago Transit Authority)|Pink]] and [[Green Line (Chicago Transit Authority)|Green]] lines and the looping [[Orange Line (Chicago Transit Authority)|Orange line]] above the [[Wells Street (Chicago)|Wells]] and [[Lake Street (Chicago)|Lake street]] [[intersection (road)|intersection]] in the [[Loop (CTA)|loop]].]]

A '''junction''', in the context of [[rail transport]], is a place at which two or more rail routes converge or diverge. The physical connection between the tracks of the two routes (assuming they are of the same gauge) is provided by [[Railroad switch|turnouts]] (US: [[railroad switch|switch]]es) and [[railway signalling|signalling]].<ref>{{cite book| title=Railway Junction Diagrams | first=John | last=Airey | edition=reprint | publisher=[[BiblioBazaar]] | year=2010 | isbn=9781145129566 }}</ref>

==Overview==
In a simple case where two routes with one or two tracks each meet at a junction, a fairly simple layout of tracks suffices to allow trains to transfer from one route to the other. More complicated junctions are needed to permit trains to travel in either direction after joining the new route – for example by providing a triangular track layout.<ref group="note">In this latter case, the three points of the triangle may be given different names, for example using points of the compass as well as the name of the overall place.</ref>

[[Rail transport operations]] refer to [[railway station|station]]s that lie on or near a railway junction as a ''[[junction station]]''. In the UK it is customary for the junction (and the related station) to be named after the next station on the branch, e.g. [[Yeovil Junction railway station|Yeovil Junction]] is on the mainline railway south of [[Yeovil]], and the next destination on the branch is [[Yeovil Pen Mill railway station|Yeovil Pen Mill]]. Frequently, trains are built up and taken apart (separated) at such stations so that the same train can be divided and proceed to multiple destinations. For [[goods train]]s (US: freight trains), marshalling yards (US: [[Classification yard]]s) serve a similar purpose.

==Measures to improve junction capacity==
The capacity of the junctions limits the capacity of a [[railway network]] more than the capacity of individual [[railway line]]s. This applies more as the network density increases. Measures to improve junctions are often more useful than building new railway lines. The capacity of a railway junction can be increased with improved [[Railway signaling|signaling]] measures, by building points suitable for higher speeds, or by turning [[level junction]]s into [[flying junction]]s, where tracks are [[grade separation|grade-separated]], and so one track passes over or under another.<ref>{{cite web |last1=Woodcock |first1=Ian |title=Of Skyrails and Skytrains - Elevated rail in the Australasian urban transport environment |url=http://atrf.info/papers/2016/files/ATRF2016_Full_papers_resubmission_129.pdf |website=Australian Transport Research Forum |access-date=16 September 2018 |archive-date=16 September 2018 |archive-url=https://web.archive.org/web/20180916060205/http://atrf.info/papers/2016/files/ATRF2016_Full_papers_resubmission_129.pdf |url-status=dead }}</ref> With more complicated junctions such construction can rapidly become very expensive, especially if space is restricted by [[tunnel]]s, [[bridge]]s or inner-city tracks.

==Avoiding the need for junctions==

The installation of junctions into a rail system poses many challenges, including increased maintenance costs, and problems in on-time performance. [[Rapid transit|Metro rail systems]] have a rail network design where the number of junctions is minimized. Passengers, and not trains, move from one [[rail station|train station]] to another.


== Gallery ==
<gallery class="center" widths="200px" heights="200px">
File:Track of Singapore LRT 002.jpg|Junction in track of [[Singapore LRT]]
File:Cardiff Queen Street - view north - 02.jpg|A [[double junction]] in [[Cardiff]], [[Wales]]
File:Baranowicze WIG 1934.jpg|A junction in [[Baranowicze]], Poland, 1934 (since 1939 in [[Belarus]])
File:KatniJunctionMadhyaPradesh2010.jpg|A train passing through [[Katni Junction railway station|Katni Junction]] in Madhya Pradesh, India
</gallery>

==See also==
{{div col|colwidth=23em}}
<!---♦♦♦ Please keep the list in alphabetical order  ♦♦♦--->
* [[Diamond crossing]]
* [[Double junction]]
* [[Interlocking]]
* [[Junction (traffic)]]
* [[Level junction]]
* [[Railroad switch]]
{{div col end}}

==Notes==
{{Reflist|group=note}}

==References==
{{reflist}}

==External links==
*{{Commonscatinline}}

{{Railway track layouts}}
{{Rail tracks}}

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[[Category:Train-related introductions in 1831]]
[[Category:1831 in rail transport]]
[[Category:1831 establishments in England]]
[[Category:Rail junctions| ]]
[[Category:Rail junction types| ]]
[[Category:Railway track layouts]]
[[Category:Permanent way]]