Flying junction
This articleneeds additional citations forverification.(June 2011) |
Aflying junctionorflyoveris arailway junctionat 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 "grade-separated junction".Aburrowing junctionordive-underoccurs where the diverging line passes below the main line.
The alternative to grade separation is alevel junctionor flat junction, where tracks crossat grade,and conflicting routes must be protected by interlockedsignals.
Complexity
[edit]Simple flying junctions may have a single track pass over or under other tracks to avoid conflict, while complex flying junctions may have an elaborateinfrastructureto allow multiple routings without trains coming into conflict, in the manner of a highwaystack interchange.
Flying junction without crossings
[edit]Where two lines each of two tracks merge with a flying junction, they can become afour-track railwaytogether, the tracks paired by direction. This happens regularly in the Netherlands (seeExamplesbelow).
High-speed rail
[edit]Nearly all junctions withhigh-speed railwaysare grade-separated. On the FrenchLignes à Grande Vitesse(TGV) high-speed network, the principal junction on theLGV Sud-Est,at Pasilly where the line to Dijon diverges, and on theLGV Atlantiqueat Courtalain where the line to Le Mans diverges, are fully grade-separated with special high-speed switches (pointsin British terminology) that permit the normal line speed of 300 km/h (186 mph) on the main line, and a diverging speed of 220 km/h (137 mph).[note 1]
The LGV network has four grade-separated high-speed triangles: Fretin (near Lille), Coubert (southeast Paris), Claye-Souilly (northeast Paris) and Angles (Avignon). A fifth, Vémars (northeast Paris), is grade-separated except for a single-track link on the least-used side, linkingParis Gare du NordandParis CDGairport.
Examples
[edit]- Australia
- Bowen Hills railway stationinBrisbane
- Burnley railway stationinMelbourne
- Camberwell railway stationin Melbourne
- Sydney Central Station
- Glenfield railway station, Sydney
- Strathfield railway station
- Sandgate Flyover,Newcastle– main line flies over coal branch line
- Goodwood railway stationinAdelaide
- Bayswater railway stationinPerth
- Canada
- Columbia stationin New Westminster, BC –Expo Linebranches forKing George(top) andProduction Way–University(bottom)
- Bridgeport stationin Richmond, BC –Canada Linebranches forYVR–AirportandRichmond–Brighouse
- Denmark
- Hvidovre, Copenhagen (55°39′51″N12°29′01″E/ 55.664158°N 12.483701°E)
- Junction of M1 and M2 lines on theCopenhagen Metro
- Lunderskov (55°28′26″N9°18′04″E/ 55.473772°N 9.301164°E)
- Roskilde, south of (55°36′27″N12°02′47″E/ 55.607374°N 12.046496°E)
- Sydhavnen, Copenhagen (55°38′29″N12°32′54″E/ 55.641273°N 12.548343°E)
- Vigerslev, Copenhagen (55°39′26″N12°30′18″E/ 55.657331°N 12.505050°E)
Finland
- Railway junction of two main lines at Kytömaa,Kerava
- France (LGV Triangles)
- Triangle de Fretin, Lille, connecting Paris, Brussels and London
- Triangle de Coubert, Paris
- Triangle des Angles, Avignon, with two parallel 1.5-kilometre (0.93 mi) viaducts
- Triangle de Claye-Souilly, Paris, partial four-way junction
- Triangle de Vémars, Paris
- Germany
- Hong Kong
- WhereAirport ExpressandTung Chung linediverge from each other atTai Ho Wan
- Tseung Kwan O lineto the east ofTseung Kwan O station
- Netherlands
There are between 25 and about 40 flying junctions on Dutch railways, depending on how more complex examples are counted.
- NearHarmelen.Before conversion to a flying junction, this was the site of theHarmelen train disaster.
- AtBreukelen railway station
- AtLage Zwaluwe railway station
Flying junctions where the merged lines become a four track railway:
- NearDen Haag Laan van NOI railway station
- North ofLeidenwhere lines fromHaarlemandSchipholmerge
- AtBoxtel railway stationwhere lines from's-HertogenboschandTilburgmerge
- West ofGoudawhere lines fromRotterdamandThe Haguemerge
More complex flying junctions, with tracks from four directions joining:
- AroundAmsterdam Sloterdijk railway station
- AroundDuivendrecht railway station
- Northwest exit ofUtrecht Centraal railway station
- West and northwest exit ofRotterdam Centraal railway station
- At both sides ofWeesp railway station(see diagram at right)
- Norway
- Lillestrøm (59°57′09″N11°01′39″E/ 59.952571°N 11.027455°E)
- Lysaker (59°54′54″N10°37′40″E/ 59.914903°N 10.627711°E)
- Sandvika, east of and west of (59°53′47″N10°32′10″E/ 59.896373°N 10.536113°E) (59°53′26″N10°30′29″E/ 59.890663°N 10.508148°E)
- Sweden
- Flemingsberg (59°12′51″N17°56′22″E/ 59.214247°N 17.939363°E)
- Järna, north of (59°07′18″N17°36′47″E/ 59.121566°N 17.613176°E)
- Järna, south of (59°04′17″N17°32′23″E/ 59.071478°N 17.539807°E)
- Lund (55°42′44″N13°11′08″E/ 55.712348°N 13.185570°E)
- Hyllie (55°33′32″N12°57′42″E/ 55.558971°N 12.961761°E)
- Myrbacken (59°40′41″N17°49′37″E/ 59.678161°N 17.826828°E)
- Lernacken (55°33′46″N12°55′54″E/ 55.562779°N 12.931545°E)
- Södertälje hamn (59°10′54″N17°38′37″E/ 59.181793°N 17.643503°E)
- Södertälje syd (59°09′34″N17°38′14″E/ 59.159427°N 17.637278°E)
- Tomteboda (59°21′10″N18°00′56″E/ 59.352646°N 18.015546°E)
- Taiwan
- Start ofShalun line,south ofZhongzhou railway station
- United Kingdom
- PelawJunction where both theTyne and Wear Metrogreen line toSouth Hyltonjoins theDurham Coast Lineand yellow line continues toSouth Shields– both diverging on the bridge itself
- Springhead Junction on theNorth Kent Line
- Southfleet Junction on theHS1
- Norton Bridge Junctionnear Stone, Staffordshire
- Hamilton Square underground station,Birkenhead,onMerseyrail
- Aynho JunctioninAynho,Northamptonshire
- Worting JunctionnearBasingstoke,Hampshire(the flyover is called Battledown Flyover)
- Cogload JunctionnearTaunton
- Weaver JunctionnearDutton, Cheshire
- Shortlands Junctionin south London
- Northwest of Harrow-on-the-Hill,in the north London suburbs
- Hitchin flyover,Hertfordshire.
- Werrington Junction dive-under,northern suburbs ofPeterborough,Cambridgeshire
- ReadingWest Junction
- Bleach Green Viaducts& Junction,Whiteabbey,Northern Ireland
- Manchester Metrolink,Greater Manchester,immediately southwest ofCornbrook tram stopwhere theEccles Linediverges from theAltrincham Line.
- United States
- Northeast U.S. (Amtrak)
- Along theNew York–Washingtonsection of theNortheast Corridor,and on the Philadelphia–Harrisburgsection of theKeystone Corridor.Both converge atZoo Junctionnear30th Street Stationin Philadelphia. All were built by the formerPennsylvania Railroadand are now maintained by Amtrak.
- Boston,Massachusetts area
- An abandoned underground junction on theTremont Street subwayapproaching thePleasant Street incline
- The B branch splits off from the C and D branches of theMBTAGreen Linevia an underground flying junction just west ofKenmore station.
- The Union Square spur splits off from theGreen Line Extensionof theMBTAGreen Linevia an aerial flying junction on the Red Bridge viaduct in the Inner Belt area ofSomerville, Massachusettsjust north ofLechmere stationin Cambridge. Lead tracks to the GLX maintenance facility also split off from the junction slightly further west.
- The two southern branches of theMBTARed Linein Boston split via a flying junction just north ofJFK/UMass station.In addition, lead tracks to Cabot Yard maintenance facilities branch off from the junction.
- Chicago,Illinois
- On theChicago "L",whereOrange Linetrains diverge fromGreen Linetrains north of 18th Street, as well as underground where a non-revenue flying junction separatesRed Linetrains heading to95thfrom those heading to theSouth Side main line,currently used to send some rush-period Red Line trains toAshland/63rd.
- TheMilwaukee–Dearborn subway(now part of theBlue Line) was constructed to have a flying junction where turning between Lake Street and Milwaukee Avenue at Canal Street. The outbound tunnel and its stub, designed to continue west under Lake Street, was bored at less depth than the inbound tunnel and its Lake Street stub, in order to allow future Lake Street trains (now part of theGreenand (Pink Lines) to run under or over the opposing Milwaukee Avenue trains while entering or exiting the shared portion of the Lake Street tunnels. Plans in 1939 called for tunnels to replace the elevated Lake Street tracks east of approximately Racine Avenue.[1][2]By 1962, the planned Lake Street tunnels to/from Racine Avenue would have curved south to Randolph Street and bypassed the Milwaukee-Lake-Dearborn tunnel entirely.[3]
- Another flying junction is under construction immediately north ofBelmont/Sheffieldto increase capacity on the Red Line,Brown Line,andPurple Line Express.
- Denver,Colorado
- On theRegional Transportation Districtin Denver between the Southeast Corridor and the I-225 Corridor: the Southeast Corridor is on the west side of I-25 and the I-225 Corridor is in the median of I-225. The grade separations of the junction are woven into the grade separations of the interchange between the two highways.
- New York,New York
- On theNew York City Subwaythere is an above-ground example at Hammel's Wye on theIND Rockaway Line,as well as numerous below-ground examples across the network
- ConnectingMetro-North Railroad'sNew Haven LineandHarlem Line,nearWakefieldstation in theBronx
- Philadelphia,Pennsylvania
- Amtrak'sZoo Junction,where theNortheast Corridormeets theKeystone Corridorand sorts into30th Street Station's lower and upper level platforms. Also known as Zoo Interlocking, the name comes from thePhiladelphia Zoo,which is located in the crescent shaped pocket between the junction and the river.
- OnSEPTA'sCynwyd Line,diverging from the Keystone Corridor west of52nd Street.
- On SEPTAAirport Line,diverging from the Northeast Corridor south ofPenn Medicine
- On SEPTA'ssubway–surface trolley lines,where the Route 10 diverges from Routes 11/13/34/36 west of33rd Street.
- On SEPTA'sBroad Street subway,where Broad-Ridge Spur trains diverge atFairmount.There are also provisions for flying junctions north ofEriefor the Roosevelt Boulevard Subway, and north ofOlneyfor an extension on North Broad Street; both are maintained as layup tracks.
- San Francisco Bay Area,California
- TheOakland Wye,where all ofBay Area Rapid Transit's mainline operations converge near downtownOakland
- On theMarket Street subwayinSan Franciscowhere theJ ChurchandN Judahlines join the main line of the subway. The subway portal is east of the intersection of Church Street and Duboce Avenue in theDuboce Triangleneighborhood, immediately north of aSafewaysupermarket and south of theSan Francisco branch of the United States Mint.
- Washington,District of Columbia
- All main-line connections on theWashington Metro– adjacent to the Pepco power plant on Benning Road (near the Stadium-Armory station) is a large three-track structure with a turnback pocket where the Blue, Silver and Orange Lines meet. This would have been part of the Oklahoma Avenue station, had it been built. South of the King Street station in Alexandria is a series of tunnels where the Blue and Yellow Lines meet. There are also flying junctions near three underground rail stations: Rosslyn (Blue, Silver, and Orange Lines), L'Enfant Plaza (Green and Yellow lines), and the Pentagon (Blue and Yellow lines).
See also
[edit]Notes
[edit]- ^See "Courtalain"on the French language Wikipedia.
References
[edit]- ^City of Chicago, Department of Subways and Traction,Second Annual Report of the Department of Subways and Traction, City of Chicago, for the Year Ending December 31, 1940(Chicago: City of Chicago, December 31, 1940).
- ^Chicago Department of Subways and Traction,Comprehensive Plan,2-29, III-VII.
- ^Chicago Transit Board,Plan for Expanding Rapid Transit Service in the Central Area of Chicago(Chicago: Chicago Transit Board, April 20, 1962).
External links
[edit]- WikiMapia link – aerial photo of Fretin triangle (mentioned above)
- Photo link – flying junction on Pennsylvania Railroad north of 30th Street Station, Philadelphia, Pennsylvania, United States
- Photo link – simpler flying junction at terminus of Market–Frankford transit line, 69th Street Station, Philadelphia, Pennsylvania, United States