A junction, in the context of rail transport, is a place at which two or more rail routes converge or diverge. This implies a physical connection between the tracks of the two routes (assuming they are of the same gauge), provided by ''points'' (US: switches) and signalling. Junctions are important for rail systems, their installation into a rail system can expand route capacity, and have a powerful impact upon on-time performance.

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. 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. Rail transport operations refer to

station Station may refer to: Agriculture * Station (Australian agriculture), a large Australian landholding used for livestock production * Station (New Zealand agriculture), a large New Zealand farm used for grazing by sheep and cattle ** Cattle statio ...

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 Yeovil Junction railway station is the busier, but less central, of two railway stations serving the town of Yeovil in England. The station is outside the town, in the village of Stoford. Although Yeovil is in Somerset, the station was in Dor ...

is on the mainline railway south of Yeovil, and the next destination on the branch is 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 trains (US: freight trains), marshaling yards (US: Classification yards) serve a similar purpose. The world's first railway junction was Newton Junction (now Earlestown station) near

Newton-le-Willows Newton-le-Willows is a market town in the Metropolitan Borough of St Helens, Merseyside, England. The population at the 2011 census was 22,114. Newton-le-Willows is on the eastern edge of St Helens, south of Wigan and north of Warrington. The ...

, England where, in 1831, two railways merged.

Measures to improve junction capacity

The capacity of the junctions limits the capacity of a

railway network Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in Track (rail transport), tracks. In contrast to road transport, where the ...

more than the capacity of individual railway lines. 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

signaling In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

measures, by building points suitable for higher speeds, or by turning level junctions into flying junctions, where tracks are

grade-separated In civil engineering (more specifically highway engineering), grade separation is a method of aligning a junction of two or more surface transport axes at different heights (grades) so that they will not disrupt the traffic flow on other tran ...

, and so one track passes over or under another. With more complicated junctions such construction can rapidly become very expensive, especially if space is restricted by tunnels, bridges 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. Metro rail systems have a rail network design where the number of junctions is minimized. Passengers, and not trains, move from one train station to another.

Gallery

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 in Madhya Pradesh, India

References

External links