A junction, in the context of

rail transport 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 tracks. In contrast to road transport, where the vehicles run on a p ...

, 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:

switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...

es) and

signalling 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'' ...

. Junctions are important for rail systems, their installation into a rail system can expand

route capacity Route capacity is the maximum number of vehicles, people, or amount of freight than can travel a given route in a given amount of time, usually an hour. It may be limited by the worst bottleneck (engineering), bottleneck in the system, such as a ...

, and have a powerful impact upon

on-time performance In public transportation, schedule adherence or on-time performance refers to the level of success of the service (such as a bus or train) remaining on the published schedule. On time performance, sometimes referred to as on time running, is normal ...

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 Rail transport operations are the day-to-day operations of a railway. A railway has two major components: the infrastructure (the permanent way, tracks, stations, freight facilities, viaducts, tunnels, etc.) and the rolling stock (the locomotiv ...

refer to stations that lie on or near a railway junction as a ''

junction station ''Junction station'' usually refers to a railway station situated on or close to a junction where lines to several destinations diverge. The usual minimum is three incoming lines. At a station with platforms running from left to right, the minimum ...

''. 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 is on the mainline railway south of

Yeovil Yeovil ( ) is a town and civil parishes in England, civil parish in the district of South Somerset, England. The population of Yeovil at the last census (2011) was 45,784. More recent estimates show a population of 48,564. It is close to Somer ...

, and the next destination on the branch is

Yeovil Pen Mill Yeovil Pen Mill railway station is one of two stations serving the town of Yeovil, Somerset, England. The station is situated just under a mile to the east of the town centre. The station is located south of , on the Heart of Wessex Line. The ...

. 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 Rail freight transport is the use of railroads and trains to transport cargo as opposed to human passengers. A freight train, cargo train, or goods train is a group of freight cars (US) or goods wagons (International Union of Railways) hauled ...

s (US: freight trains), marshaling yards (US:

Classification yard A classification yard (American and Canadian English ( Canadian National Railway use)), marshalling yard (British, Hong Kong, Indian, Australian, and Canadian English ( Canadian Pacific Railway use)) or shunting yard (Central Europe) is a railway ...

s) serve a similar purpose. The world's first railway junction was Newton Junction (now Earlestown station) near Newton-le-Willows,

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

where, in 1831, two railways merged.

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 Rail terminology is a form of technical terminology. The difference between the American term ''railroad'' and the international term ''railway'' (used by the International Union of Railways and English-speaking countries outside the United Sta ...

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

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 junction A level junction (or in the United Kingdom a flat crossing) is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front o ...

s into

flying junction A flying junction or flyover is a railway junction at which one or more diverging or converging tracks in a multiple-track route cross other tracks on the route by bridge to avoid conflict with other train movements. A more technical term is "gr ...

s, 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

tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube cons ...

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...

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. Metro rail systems have a rail network design where the number of junctions is minimized. Passengers, and not trains, move from one

train station A train station, railway station, railroad station or depot is a railway facility where trains stop to load or unload passengers, freight or both. It generally consists of at least one platform, one track and a station building providing suc ...

to another.

Gallery

File:Track of Singapore LRT 002.jpg, Junction in track of

Singapore LRT The Light Rail Transit (LRT) is a series of localised automated guideway transit systems acting as feeder services to the heavy rail Mass Rapid Transit, which together forms the core of Singapore's rail transport services. The first LRT line ...

File:Cardiff Queen Street - view north - 02.jpg, A

double junction A double junction is a railway junction where a double-track railway splits into two double track lines. Usually, one line is the main line and carries traffic through the junction at normal speed, while the other track is a branch line that c ...

Cardiff Cardiff (; cy, Caerdydd ) is the capital and largest city of Wales. It forms a principal area, officially known as the City and County of Cardiff ( cy, Dinas a Sir Caerdydd, links=no), and the city is the eleventh-largest in the United Kingd ...

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

File:Baranowicze WIG 1934.jpg, A junction in

Baranowicze Baranavichy ( ; be, Бара́навічы, Łacinka: , ; russian: Бара́новичи; yi, באַראַנאָוויטש; pl, Baranowicze) is a city in the Brest Region of western Belarus, with a population (as of 2019) of 179,000. It is no ...

, Poland, 1934 (since 1939 in

Belarus Belarus,, , ; alternatively and formerly known as Byelorussia (from Russian ). officially the Republic of Belarus,; rus, Республика Беларусь, Respublika Belarus. is a landlocked country in Eastern Europe. It is bordered by R ...

) File:KatniJunctionMadhyaPradesh2010.jpg, A train passing through

Katni Junction Katni Junction (Station Code: KTE) is a major rail junction in Katni, India. Rail links from the junction travel in five directions — Bina, Jabalpur, Satna, Bilaspur, Singrauli. Rail links from the junction travel to New Delhi, Mumbai, Vadoda ...

in Madhya Pradesh, India

References

External links