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Anisland platform (alsocenter platform (American English) orcentre platform (British English)) is a station layout arrangement where a singleplatform is positioned between twotracks within arailway station,tram stop ortransitway interchange.[1] Island platforms are sometimes used between the opposite-direction tracks on twin-track route stations as they are cheaper and occupy less area than other arrangements. They are also useful within larger stations, where local and express services for the same direction of travel can be accessed from opposite sides of the same platform instead ofside platforms on either side of the tracks, simplifying and speeding transfers between the two tracks.
The historical use of island platforms depends greatly upon the location. In the United Kingdom the use of island platforms on twin-track routes is relatively common when the railway line is in acutting or raised on anembankment, as this makes it easier to provide access to the platform without walking across the tracks.
Island platforms are necessary for any station with many through platforms. There are also advantages to building small two-track stations with a single island platform instead of two side platforms. Island platforms allow facilities such as shops, toilets and waiting rooms to be shared between both tracks rather than being duplicated or present only on one side. An island platform makes it easier for disabled travellers to change services between tracks or access facilities. If the tracks are above or below the entrance level, the station needs only one staircase and one elevator or ramp to allow step-free access to the platforms. If the tracks are at the same level as the entrance, this instead creates a disadvantage; a side platform arrangement allows one platform to be adjacent to the entrance, whereas an island platform arrangement requires both tracks to be accessed by a bridge or underpass.
If an island platform is not wide enough to cope with passenger numbers, typically as they increase, overcrowding can risk people being pushed onto the tracks. In some cases, entry to the station is restricted at busier times to reduce risk.[2] Examples of stations where a narrow island platform has caused safety issues includeClapham Common andAngel (rebuilt in 1992) on theLondon Underground,Union (rebuilt in 2014) on theToronto subway, andUmeda on theOsaka Municipal Subway.
An island platform requires the tracks to diverge around the centre platform, and extra width is required along the right-of-way on each approach to the station, especially on high-speed lines. Track centres vary for rail systems throughout the world but are normally 3 to 5 metres (9 ft 10 in to 16 ft 5 in). If the island platform is 6 metres (19 ft 8 in) wide, the tracks must slew out by the same distance. While this requirement is not a problem on a new line under construction, it makes building a new station on an existing line impossible without altering the tracks. A single island platform also makes it quite difficult to have through tracks (used by trains that do not stop at that station), which are usually between the local tracks (where the island would be).
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A common configuration in busy locations on high speed lines is a pair of island platforms, with slower trains diverging from the main line (or using a separate level on the railway'sright-of-way) so that the main line tracks remain straight. High-speed trains can therefore pass straight through the station, while slow trains pass around the platforms (such as atKent House inLondon). This arrangement also allows the station to serve as a point where slow trains can be passed by faster trains. A variation at some stations is to have the slow and fast pairs of tracks each served by island platforms (as is common on theNew York City Subway; theBroad Street Line ofPhiladelphia; and theChicago Transit Authority'sRed andPurple lines).
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A rarer layout, present atMets-Willets Point on theIRT Flushing Line,34th Street – Penn Station on theIRT Seventh Avenue Line and34th Street – Penn Station on theIND Eighth Avenue Line of theNew York City Subway, uses two side platforms for local services with an island in between for express services. The purpose of this atypical design was to reduce unnecessary passenger congestion at a station with a high volume of passengers. Since theIRT Seventh Avenue Line andIND Eighth Avenue Line have adjacent express stations at 42nd Street, passengers can make their transfers from local to express trains there, leaving more space available for passengers utilizing intercity rail atPennsylvania Station. TheWillets Point Boulevard station was renovated to accommodate the high volume of passengers coming to the1939 World's Fair.
Many of the stations on theGreat Central Railway inEngland (now almost entirely closed) were constructed in this form. This was because the line was planned to connect to aChannel Tunnel. If this happened, the lines would need to be compatible with continentalloading gauge, and this would mean it would be easy to change the line to a larger gauge, by moving the track away from the platform to allow the wider bodied continental rolling stock to pass freely while leaving the platform area untouched.
Almost all railway stations inIndia have island platforms.[citation needed]
InSydney, on theEastern Suburbs Railway and theSydney MetroNorth West and Bankstown Line, the twin tunnels are widely spaced and the tracks can remain at a constant track centres while still leaving room for the island platforms. Newer stations with island platforms includeEdmonson Park andLeppington. Older stations includeMilsons Point, and all stations betweenWaitara andArtamon on theT1 North Shore Line. Most stations betweenFlemington up toSt Marys feature two pairs of island platforms, while most stations on theT6 Lidcombe and Bankstown Line contain island platforms. All stations betweenTurella andPanania on the T8 Airport and South Line are in an island platform arrangement (withRevesby having two island platforms), whileArncliffe,Hurstville,Oatley, and the entireCronulla Branch (exceptCronulla itself) on theT4 Eastern Suburbs and Illawarra Line are some other examples.
Examples inMelbourne includeWest Footscray,Middle Footscray,Albion andTottenham on theSunbury line,Kananook on theFrankston Line,Aircraft,Williams Landing andHoppers Crossing on theWerribee Line,Ardeer,Caroline Springs on theBallarat Line,Glen Iris,Holmesglen,Jordanville andSyndal on theGlen Waverley Line, andWatsonia andHeidelberg on theHurstbridge line.
Most ofPerth's railway stations are in an island platform arrangement, this is very common on older legacy lines and almost all newer built lines byMetronet. All stations on theEllenbrook Line and theAirport Line have island platforms.
InToronto, 29 subway stations use island platforms (a few in the newer stations on theBloor–Danforth line, a few on theYonge–University line and all of theSheppard line).
InEdmonton, all 18 LRT stations on theCapital Line andMetro Line used island platforms untilNAIT/Blatchford Market station opened in 2024, the only station with side platforms as of 2024. TheValley Line Southeast uses low-floor LRT technology, but uses island platforms on only two of the 12 stops,Mill Woods andDavies.
Almost all of the elevated stations inSingapore'sMass Rapid Transit (MRT) system use island platforms. The exceptions areDover MRT station andCanberra MRT station, which use side platforms as they are built on an existing rail line, also known as aninfill station. The same follows for underground stations, with the exception beingBraddell MRT station,Bishan MRT station, and a few stations on theDowntown line (Stevens,Downtown,Telok Ayer,Chinatown andMacPherson) and theThomson-East Coast line (Napier,Maxwell,Shenton Way andMarina Bay)
In southernNew Jersey andPhiladelphia,PATCO uses island platforms in all of its 13 stations to facilitateone-person train operation.
TheNYC Subway has many stations with island platforms, including all of theSecond Avenue Subway stations.[3]
Sometimes when the track on one side of the platform is unused by passenger trains, that side may be fenced off. Examples includeHurlstone Park,Lewisham, Sydney andYeronga, Brisbane.
In New York City'ssubway system, unused sides are located atBowling Green as well as every express station without express service, such asPelham Parkway on the IRT Dyre Avenue line. In Jersey City, theNewportPATH station has the same configuration as Bowling Green—one side platform and one island platform.
On theTokyo Metro, theGinza Line has a side platform and an island platform atNihombashi. Likewise, theNamba andMinami-morimachi stations on theOsaka Metro have similar configurations. On JR East, theYokosuka Line platforms atMusashi-Kosugi feature a similar setup following a new side platform opening in December 2022.[4]
Some stations of theGlasgow Subway have one island platform and one side platform (Hillhead,Buchanan Street, andIbrox).
InWellington, New Zealand, unused sides can be found at two stations on theHutt Valley Line:Waterloo andPetone. Waterloo's island platform was reconfigured to be the down side platform when the station was extensively rebuilt in the late 1980s, with the unused side now facing onto a bus bay. Petone's island platform served the up main line and the suburban loop line until the suburban loop was lifted in the early 1990s. The unused platform now faces onto the station's park-and-ride carpark.
