A split platform is a station that has a platform for each track, split onto two or more levels. This configuration allows a narrower station plan (or footprint) horizontally, at the expense of a deeper (or higher) vertical elevation, because sets of tracks and platforms are stacked above each other. Where two rails lines cross or run parallel for a time, split platforms are sometimes used in a hybrid arrangement that allows for convenient cross-platform interchange between trains running in the same general direction.
On the London Underground, to minimise the risk of subsidence, the tunnel alignments largely followed the roads on the surface and avoided passing under buildings.[note 1] If a road was too narrow to allow the construction of side-by-side tunnels, they would be aligned one above the other, so that a number of stations have platforms at different levels.
This setup is not common in North American railroad stations, but is found in places in Europe such as the London Underground on the deep tube lines, namely the Bakerloo, Central, Jubilee, Northern and Piccadilly lines.[note 2]
Examples of split platform layout in the United States are Rosslyn on the Washington Metro's Blue and Orange Lines; Pentagon on the Washington Metro's Blue and Yellow Lines; and Harvard and Porter stations on the Boston-Cambridge MBTA Red Line. Split platforms are also at downtown Oakland, California on BART's 12th and 19th Street, and at Los Angeles Metro Rail's Wilshire/Vermont. MARTA's Ashby station uses the configuration to separate the eastbound and westbound platforms.
In the New York City Subway, Nostrand Avenue and Kingston Avenue stations on the IRT Eastern Parkway Line have two tracks on each level, with each of the two levels serving trains in one direction. Further north on the Eastern Parkway line, Borough Hall also has split platforms. Also, stations on the IND Eighth Avenue Line have split stacked platforms between 59th Street – Columbus Circle] and Cathedral Parkway – 110th Street due to the proximity of the line to Central Park. In other stations like Fulton Street, Borough Hall, and Fifth Avenue / 53rd Street, platforms are stacked due to the narrowness of the street directly above the station. One notable station, Wilson Avenue on the BMT Canarsie Line, has one elevated platform and one at-grade platform, due to the narrowness of the line's right-of-way.
In Canada, split platforms on the Montreal Metro are located at De L'Église and Charlevoix and the Blue Line platforms at Jean-Talon, while Snowdon and Lionel-Groulx have a hybrid layout where the two directions on each line are split from each other but sharing an island platform with the other line. They are also found on Vancouver's SkyTrain, at the stations in the Dunsmuir Tunnel and at the King Edward station on the Canada Line.
Milan Metro Sant'Agostino on line M2 is similar, and also all the stations between Crocetta and Turati on line M3.
On Munich Marienplatz Station the Munich S-Bahn (suburban trains) are on two separate levels, where westbound trains depart from the lower level, eastbound trains from the upper level. Below the westbound level there is an interchange to the metro lines U3 and U6 in North-South direction.
In Nuremberg metro network, the station Plärrer has two platforms for cross-platform interchange between lines U1 and U2/U3. The upper platform is used for westbound/outbound services, while the lower one is designated for eastbound/inbound trains.
In Hanover light-metro network, Kröpcke has three levels, one for blue lines (3, 7 and 9); SW to NE, one for red lines (1, 2 and 8); NW to SE and one for yellow lines (4, 5, 6 and 11). The red lines level and the yellow lines level are situated directly below each other. An interchange between red and yellow lines is possible at Aegidientorplatz where the underground platforms are situated the same way like Nürnberg Plärrer. Eastbound/outbound trains use the lower platform, westbound/inbound trains use the upper one.
On Vienna U-Bahn line U3, the stations Neubaugasse, Zieglergasse, Herrengasse, Stephansplatz and Stubentor have two levels of platforms. Trains towards Ottakring (westbound) use the lower platform, trains towards Simmering the upper one. In Stephansplatz the line U1 crosses below these platforms.
In Asia, Jingan and Yongan Market on the Taipei Metro have split stacked platforms, and Central, Wan Chai, Causeway Bay, Tin Hau, North Point, and Sai Wan Ho on MTR's Island Line on Hong Kong Island all have split platforms. Promenade and Stevens Station in Singapore and Bukit Bintang MRT station in Malaysia also have split side platforms.