Metro Rings of the WorldMetros, also called subways or underground urban railways, are abundant throughout the cities of the world. Most metro lines are straight and radial, connecting a city center with the suburbs. Only some of the lines have been designed in a circular shape. This document describes this special type of metro lines and provides a complete list of existing and envisioned rings. More than 120 metro systems currently exist throughout the world and more are under construction. Some of them contain a ring line, very few have more than one ring line. Most of the ring lines orbit the city center. Many of these rings are very old and have been built in big cities in order to connect the (often numerous) peripheral train stations of those cities. But many more rings are currently under construction or planned. This indicates that rings are still a good option to enhance the usability of existing metro networks. Facts and OdditiesThe usability of metro rings is controversial: One author [3] claims that circles are generally unsatisfactory from operational and traffic standpoints, at least if shared among different lines. Delays can accumulate along the endless tour around the circle. Another author [4] argues that the optimal type of subway network consists of several straight (radial) lines crossing through a circle line. However the radial lines should not all meet in the center of the circle but in different places within the circle. Excellent geological preconditions in London and Moscow allowed to choose optimal network types without any constraints, and in both cases the circle-radial network type has indeed been chosen. Example of a circle-radial network: Moscow 2002 (click to enlarge). Trains have to be turned around from time to time in order to prevent the wheels from wearing out unevenly [1]. Glasgow's metro network consists of a single circular line. It is nicknamed "Clockwork Orange", according to the color of the trains and the color of the line on the metro map. Madrid's circular line is said to be not very popular among the train drivers because its seemingly endless tunnel makes the drivers feel uneasy. Train directions of a circular line are prone to be confused by the passengers. This is for the most part because they have no terminal stops which can be used to name the trains. A possible way to prevent confusion is to give clockwise and counter-clockwise trains different line numbers (like S41 and S42 in Berlin). Complete ListData given in the following lists: City (line name, [characteristics,] length, number of stations, time for an entire circular ride, [inauguration of first section,] completion of ring, [abandoning of circular operation]). Genuine ringsBeijing (line 2, 28 km, 18 stns, 1984/1987)Berlin (S-Bahn lines S41/S42, 27 stns, 62 min, 1928/2002) Detroit (one-direction people mover, 4.8 km, 13 stns, 15 min, 1987) Glasgow (Circle line, 10.4 km, 15 stns, 24 min, 1896) London (Circle line, shared, 26km, 27 stns, 1863/1884) Madrid (line 6, 23km, 27 stns, 1979/1995) Madrid (line 12/MetroSur, 28 stns, 40.5 km, 2000/2003) Miami (elevated, rubber-tyred, automated people mover, 3 km, 8 stns, 1986) Moscow (Koltsevaya line, 19.4 km, 13 stns, 29 min, 1950/1954) Osaka (S-Bahn, 21.7 km, 19 stns, 1874/1898) Seoul (line 2, ~50 km, 43 stns, 84 min, 1978/1984) Sydney (monorail, 7 stns, 1988) Tokyo (S-Bahn Yamanote line, 29 stns, 34.5 km, 64 min, 1872/1914) Operationally split circlesHamburg (lines U2/U3, 17.5 km, 23 stns, 1912, circular operation quit 1973)Lisbon (Yellow/Green/Blue lines, 18 stns, 1953/1993) Melbourne (S-Bahn, shared, 5 stns, 1984) Paris (lines 2/6, ~24 km, 49 stns, 1900/1909) Vienna (lines U2/U4, 10 stns, 1978/1980) Pan-shaped loopsBucharest (line M1/M3, ~24 km, 16 stns, 1979/1989)Chicago (the Loop, shared among different lines, ~3.2 km, 9 stns, 1897) Newcastle (Yellow line, pan-shaped, 26 stns, 1980/1982) Sydney (S-Bahn, shared, pan-shaped, 6 km, 6 stns, 2000) Tokyo (O-Edo line, pan-shaped, ring section: 28 km, 26 stns, 1991/2000) Vancouver (Millennium line, pan-shaped, 22 stns, 1986/2002) Singapore (Bukit Panjang LRT, 7.8 km, 13 stns pan-shaped, 1999) Circles under constructionBarcelona (lines 1/9 or 4/9, 2010)Brussels (lines 1A/2, 18 stns, 1981/2007) Copenhagen (line M3, 16 stns) Copenhagen (S-Bahn, 20 stns) Nagoya (line 4/Meijo, 28 stns, 1965/2003) Naples (line 1, 8-shaped, 1993/2011) Oslo (line 5, 14 stns, 1898/2006) Shanghai (Pearl line, 26 stns, 2000/2004) Singapore (Punggol LRT, people mover above ground, 10.3 km, 15 stns, 2000/2004) Singapore (Sengkang LRT, 8-shaped people mover above ground, 10.7 km, 14 stns, 1998/2003) Singapore (Circle Line, 33.3 km, ca. 29 stns, 2002/2010) Projects and propositionsBelgrade (LRT circle?)Chicago (20 km, 22 stns, ~2015) Moscow (regional rail ring within city is under discussion) Rio de Janeiro (line 1) St. Petersburg (semi-circular regional rail planned) Seville (LR line 4, 19 stns) Toronto (Yellow/Purple lines) References[1] Bayman, Bob: London Underground Official Handbook. 2000.[2] Fischler, Stan: Subways of the World. 2000. [3] Garbutt, Paul: World Metro Systems. 1997. [4] Schleife, Hans-Werner; et al.: Metros der Welt. 1992. [5] Schwandl, Robert: UrbanRail.net. http://www.urbanrail.net This page: Metro Rings of the World, http://www.mic-ro.com/aktuell/metrorings.html.
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