A pocket track, tail track, or reversing siding (UK: centre siding, turnback siding) is a

rail track Railway track ( and UIC terminology) or railroad track (), also known as permanent way () or "P way" ( and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers (railroad ties in American E ...

layout which allows

train A train (from Old French , from Latin">-4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ... , from Latin , "to pull, to draw") is a series of connected vehicles th ...

s to park off the main line. This type of track layout differs from a

passing loop A passing loop (UK usage) or passing siding (North America) (also called a crossing loop, crossing place, refuge loop or, colloquially, a hole) is a place on a single line railway or tramway, often located at or near a station, where trains o ...

in that the pocket track is usually located between two main lines, rather than off to the side. Found primarily on

metro system Rapid transit or mass rapid transit (MRT) or heavy rail, commonly referred to as metro, is a type of high-capacity public transport that is generally built in urban areas. A grade separated rapid transit line below ground surface through a tu ...

rapid transit Rapid transit or mass rapid transit (MRT) or heavy rail, commonly referred to as metro, is a type of high-capacity public transport that is generally built in urban areas. A grade separation, grade separated rapid transit line below ground su ...

light rail Light rail (or light rail transit, abbreviated to LRT) is a form of passenger urban rail transit that uses rolling stock derived from tram technology National Conference of the Transportation Research Board while also having some features from ...

networks, and

tram A tram (also known as a streetcar or trolley in Canada and the United States) is an urban rail transit in which Rolling stock, vehicles, whether individual railcars or multiple-unit trains, run on tramway tracks on urban public streets; some ...

ways, a pocket track allows certain trains or trams to change direction, even on lines with high traffic flow, whilst others continue through the station. Pocket tracks also allow for the short-turning of trains, truncating services at an

intermediate station A train station, railroad station, or railway station 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 such ...

to control train frequency, truncating lower ridership lines or services at an intermediate station in the case of the DART Orange Line, reversing the direction of special event trains or congestion alleviating trains, and storing trains when not in use. They are also used at

terminal station A train station, railroad station, or railway station 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 such ...

s to allow for the construction of future extension of a rail track without disrupting existing service on the main tracks. A pocket track can have a platform on it to permit turning back of trains and letting passengers change trains, such as

Stevenage railway station Stevenage railway station serves the town of Stevenage in Hertfordshire, England. The station is around north of London King's Cross on the East Coast Main Line. The station lies just to the north of Langley junction, a grade separated junct ...

where a new platform 5 was built on a turnback siding, or Bachman station, where the pocket track is incorporated within the station to allow for trains to terminate before heading to the yard without disrupting traffic. Typically there will be two tracks, one for each direction of travel. The pocket track will be positioned between the two tracks, linked to both by

switches 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 o ...

, usually on both sides. Although most trains will pass through the station and continue in the same direction, an individual train may be directed into the pocket track by the control tower, before later exiting the pocket track and running in the opposite direction back into the station. This procedure allows a greater frequency of trains on a section of track closer to the city center, and reduced frequency on the suburban sections by allowing certain trains to run from the city center to intermediate stations, using pocket tracks to change direction within the flow of trains.

References

{{rail-stub Railway sidings