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18-553: The Oakland Wye is an underground flying wye junction in downtown Oakland, California which serves the Bay Area Rapid Transit (BART) system. Trains can switch between (a) the northbound Richmond or Antioch lines (first station: 12th Street Oakland City Center , underground), (b) the westbound San Francisco lines (first station: West Oakland , elevated), and (c) the southbound Berryessa or Dublin/Pleasanton lines (first station: Lake Merritt , underground). The Oakland Wye

36-470: A switch at the north end of the wye, injuring 14 passengers. In February 2000, automatic train controls failed due to a loose cable and trains through the Oakland Wye were forced to operate in manual and slow to 5–10 mph (8.0–16.1 km/h) when switching tracks. In February 2009, two northbound trains from West Oakland and Lake Merritt (one operating in manual mode) collided and partially derailed in

54-510: A tighter turn between Lake Merritt station and 12th Street/Oakland City Center and, consequently, lower speeds through the Wye. There is some evidence that then-Oakland mayor John C. Houlihan objected to the original 8th Street location because it threatened a store owned by a friend of his. A third track (labeled MX/CX in the above schematic diagram) connecting West Oakland, 12th Street Oakland City Center, 19th Street Oakland , and MacArthur stations

72-468: A turnback is built in the Oakland Wye. [REDACTED] Media related to Oakland Wye at Wikimedia Commons 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 " grade-separated junction ". A burrowing junction or dive-under occurs where

90-454: Is grade-separated except for a single-track link on the least-used side, linking Paris Gare du Nord and Paris CDG airport. Finland There are between 25 and about 40 flying junctions on Dutch railways, depending on how more complex examples are counted. Flying junctions where the merged lines become a four track railway: More complex flying junctions, with tracks from four directions joining: Railway junction A junction , in

108-464: Is normally used by Antioch -bound trains. Emergency exit/access points are located in a small building at 7th & Broadway with access to the A and M lines and a sidewalk hatch at 9th & Harrison with access to the A and C lines. The original operating speed through most of the Oakland Wye was intended to be 27 mph (43 km/h). Design problems led BART operations to impose a lower 18 mph (29 km/h) speed limit on most tracks. Although

126-575: Is the center of the BART system (all mileposts measure distance from the wye), and is a bottleneck for the whole system because every regularly scheduled BART train (except for the Oakland Airport Connector and eBART ) passes through it. The wye is a flying junction that is approximately centered underneath Broadway and 9th Streets. Trains coming from the underground 12th Street Oakland City Center station (with platforms on two levels) approach

144-737: The LGV Sud-Est , at Pasilly where the line to Dijon diverges, and on the LGV Atlantique at Courtalain where the line to Le Mans diverges, are fully grade-separated with special high-speed switches ( points in 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). 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),

162-472: The Wye while merging to approach 12th Street/Oakland City Center. Bypasses that would connect MacArthur and Oakland Coliseum with the Transbay Tube directly have been proposed to create express service, reduce the systemwide effects of delays in the Wye, and potentially provide an infill station at Jack London Square . Other infill stations or more frequent service may be provided in urban core areas if

180-425: The branch, e.g. Yeovil Junction is on the mainline railway south of Yeovil , and the next destination on the branch is Yeovil Pen Mill . 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 trains (US: freight trains), marshalling yards (US: Classification yards ) serve a similar purpose. The capacity of

198-430: The context of rail transport , is a place at which two or more rail routes converge or diverge. The physical connection between the tracks of the two routes (assuming they are of the same gauge) is provided by turnouts (US: switches ) and signalling . 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

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216-401: The design has since been corrected, the speed restrictions remain as a cautionary measure. The center "CX" track connecting West Oakland station to 12th Street is the only track with a higher operating speed of 36 mph (58 km/h) through the Wye. Early plans called for the Wye to be centered underneath Broadway and 8th Street, but this was later changed to Broadway and 9th. This required

234-451: The diverging line passes below the main line. The alternative to grade separation is a level junction or flat junction, where tracks cross at grade , and conflicting routes must be protected by interlocked signals . Simple flying junctions may have a single track pass over or under other tracks to avoid conflict; complex flying junctions may have elaborate infrastructure to allow multiple routings without trains coming into conflict, in

252-628: The junctions limits the capacity of a railway network more than the capacity of individual railway lines . 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 measures, by building points suitable for higher speeds, or by turning level junctions into flying junctions , where tracks are grade-separated , and so one track passes over or under another. With more complicated junctions such construction can rapidly become very expensive, especially if space

270-533: The manner of a highway stack interchange . Where two lines each of two tracks merge with a flying junction, they can become a four-track railway together, the tracks paired by direction. This happens regularly in the Netherlands (see Examples below). Nearly all junctions with high-speed railways are grade-separated. On the French Lignes à Grande Vitesse ( TGV ) high-speed network, the principal junction on

288-446: 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. Rail transport operations refer to stations that lie on or near a railway junction as a junction station . In the UK it is customary for the junction (and the related station) to be named after the next station on

306-422: The wye from underneath Broadway and those from the underground Lake Merritt station approach from approximately underneath 9th Street. Those trains coming from the elevated West Oakland station enter tunnel portals near Washington and 5th Streets before turning towards Broadway. An additional third track (labeled MX/CX in the schematic diagram) provides additional capacity between West Oakland and 12th Street, and

324-456: Was completed in 1986. Originally the MX/CX was used for peak hour service (westbound towards San Francisco in the morning, and eastbound in the evening). Since 1992, it has been used almost entirely for eastbound Yellow Line trains, allowing for cross-platform transfers with Orange Line trains. On December 17, 1992, a southbound train (operating on northbound track C1 due to maintenance ) split

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