Loop line has several meanings. * A less important line which leaves a main line and then rejoins it later, continuing in the same direction. Significantly longer than 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 or ...

, its purpose may be purely to provide a bypassing route, or it may provide a goods or passenger service in its own right, such as the Hertford Loop line. * A configuration, sometimes known as a

balloon loop A balloon loop, turning loop, or reversing loop ( North American Terminology) allows a rail vehicle or train to reverse direction without having to shunt or stop. Balloon loops can be useful for passenger trains and unit freight trains. Bal ...

horseshoe curve A horseshoe curve is a class of climbing curve in a roadbed which reverses turn direction (inflection) twice on either side of a single tight curve that varies through an angle of about 180 degrees or more. Such curves are more commonly found ...

where trains entering it turn through a half circle and return to the start of the loop facing in the opposite direction from which they came, such as the Sutton Loop. The

Darjeeling Himalayan Railway The Darjeeling Himalayan Railway, also known as the DHR or the Toy Train, is a gauge railway that runs between New Jalpaiguri and Darjeeling in the Indian state of West Bengal. Built between 1879 and 1881, it is about long. It climbs from ab ...

, a

UNESCO The United Nations Educational, Scientific and Cultural Organization is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) aimed at promoting world peace and security through international coope ...

World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for ...

railway in India has several examples of these in addition to six full zig zags and 3 complete

spirals In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are:circle route A circle route (also circumference, loop, ring route, ring line or orbital line) is a public transport route following a path approximating a circle or at least a closed curve. The expression "circle route" may refer in particular to: * a rout ...

is a totally enclosed system whereby trains always remain in the loop, as in the

Glasgow Subway The Glasgow Subway is an underground light metro system in Glasgow, Scotland. Opened on 14 December 1896, it is the fourth-oldest underground rail transit system in Europe after the London Underground, Liverpool's Mersey Railway and the Budap ...

or the London Underground Circle line (before it was extended to run over the

Hammersmith Hammersmith is a district of West London, England, southwest of Charing Cross. It is the administrative centre of the London Borough of Hammersmith and Fulham, and identified in the London Plan as one of 35 major centres in Greater London ...

branch in 2009). Some metro systems feature several circle lines at once like the

Moscow Metro The Moscow Metro) is a metro system serving the Russian capital of Moscow as well as the neighbouring cities of Krasnogorsk, Reutov, Lyubertsy and Kotelniki in Moscow Oblast. Opened in 1935 with one line and 13 stations, it was the first ...

, whose Line 5, Line 11 (unfinished as of 2022) and Line 14 are all circle routes.

References

{{Reflist Railway line types

See also

References