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A quadruple-track railway (also known as a four-track railway) is a railway line consisting of four parallel tracks, with two tracks used in each direction. Quadruple-track railways can handle large amounts of traffic, and so are used on very busy routes.
Some tracks are only tripled, having only one extra track to relieve congestion, while some tracks are sextupled, i.e., six parallel tracks with three tracks in each direction.
Advantages of quadruple track
- Quadruple track can manage a larger amount of traffic with usually twice the capacity of double track. It is often seen around large metropolis or on busy inter-city corridors.
- In quadruple track, faster trains can overtake slower ones, and quadrupling can contribute to faster operation of trains. High-speed rail of 200 km/h average speed and commuter rail of 40 km/h average can co-exist in quadruple track without interrupting each other.
- It is relatively easy to do maintenance and engineering work of tracks in quadruple line with minimum effect of train delay because double-track service is kept even if the other two double tracks are halted during the work.
Disadvantages of quadruple track
- Quadruple track costs more due to requiring more materials and increased land acquisition costs. This also applies to tunneling and bridge costs.
- When adding tracks, land acquisition can become prohibitively expensive.
- Maintenance costs are higher and often more complex as there may be more switches (points) on the track than on a two-track line (to facilitate switching from outer to inner tracks and vice versa).
- For safety, costly grade separations are almost always required.
- If needing more capacity, it can be better to add a double track along a different route, because it could improve local and regional transit much along an under-served route, and reduce land acquisition cost by choosing a less built-up area.
In quadruple track, trains are sorted in various ways in order to make maximum use of track capacity. These can include one or a combination of:
- Sorting by speed
A faster express line and a stopping local line are separated, with each having a separate pair of tracks. Construction of new double tracks dedicated to high-speed rail alongside existing conventional double track used by regional and local passenger trains and freight trains is a form of quadruple track. It increases the capacity of that route significantly, and allows for significant increases in inter-city high-speed train frequency with reduced travel times.
- Sorting by distance
Long distance inter-city rail and freight trains are separated from short distance commuter rail. This helps to prevent delays on one service affecting the other, and is commonly seen in metropolitan areas. Quadrupling may be necessary when a new commuter rail service begins to operate on an existing line. Sometimes the local trains have separate technology, such as electrical system or signalling, which requires strict separation, for example in Berlin or Copenhagen.
- Sorting by destination
When a quadruple track line divides to different destinations part way along, trains need to be sorted by their destination.
- Sorting by passenger/ freight
Passenger trains and freight trains can be separated with each different track.
A variation of this can be found on the quadruple track section of the Main North railway line in New South Wales between Waratah and Maitland where one pair of tracks are used exclusively for coal trains and the other pair are used for passenger trains and general freight. A similar process, but with all intercity and commuter passenger trains on the outer tracks and thru-freight trains on the inner tracks, was done by the Pennsylvania Railroad on its New York-Washington and Philadelphia-Pittsburgh mainlines prior to the takeover of operations by Amtrak and Conrail (and later Norfolk Southern). This is somewhat still done to this day by NS, CSX, and Conrail Shared Assets trains on Amtrak-owned trackage in the Philadelphia area.
- Other modes
As it can be seen from the pictures below in the Gallery of diagrams, the four tracks can be paired either by direction (slow/fast in each pair) or by purpose (speed or direction in each pair). Sometimes two of the tracks go more straight and with a little distance from the two other. This is a design decision when widening a double track section, and allows higher speed on the faster tracks.
- The New York Central's Water Level Route across Upstate New York was four-tracked in majority as early as 1876, claiming to be the earliest 4-tracked steel main. This was extended to Buffalo by 1936. Financial troubles and changing traffic patterns caused this to be downgraded to a double track by 1975.
- Much of Amtrak's Northeast Corridor from Washington to New Haven is a four-track line. A long exception is the segment between New Rochelle and the Sunnyside train yard in Queens, New York. In the Bronx section the Amtrak trains run separate from the New Haven Lines of the commuter rail segment. The section from Woodside, Queens, over the Hell Gate bridge to the South Bronx is three-tracked.
- The Erie Lackawanna Railway had a four track main line on the former Erie Railroad, from its Pavonia Terminal in Jersey city to Suffern yard in Rockland County, New York. This allowed separation of freight and commuter trains. The EL Rwy also inherited former Lackawanna four-track Boonton Main Line from Dover, NJ, to Delawanna (Passaic), NJ.
- The Central Railroad of New Jersey had a four track main from the CNJ Terminal in Jersey City to Phillipsburg, NJ, across from Easton, PA.
- The Long Island Railroad's Main Line is four-tracked from its portal in Long Island City to Floral Park, NY.
- The Pennsylvania Railroad had a four-track mainline carrying freight from Pittsburgh to Harrisburg via the Horseshoe Curve (Pennsylvania). This was how the name Broadway Limited came about from the "Broadway of a 4-track main." Much of the route between Pittsburgh and Paoli has been downgraded to three or two tracks.
- The BNSF Racetrack in Chicago has a quadruple track section from Union Station to LaVergne.
- The Chicago L has a four-track section on the Purple, Red and Brown Lines between Howard and Fullerton.
- New York City Subway – many lines of the New York City Subway are quadrupled. Hence, many express services are operated in the New York City Subway. Express trains and local trains are separated with each different track.
- SEPTA's Center City Commuter Connection in Philadelphia is quadruple track, as is much of Philadelphia's Broad Street Subway.
- Significant lengths of the West Coast, Great Western and East Coast Main Lines in Great Britain are quadruple track, with the remainder of the lines being double track. These lines are high capacity and high speed lines running from Glasgow, Bristol and Edinburgh to London.
- The London Waterloo to Southampton / Salisbury main line South Western Main Line from London Waterloo to Worting Junction, Great Britain.
- In Ireland, the busiest section of railway in the country, on the approach to Dublin's Heuston station was quadrupled in 2009.
- The Berlin Stadtbahn, Germany, has four tracks. Two are for the separated S-Bahn and two for mainline trains.
- There are two places in Denmark with four tracks: Between Klampenborg and Høje Taastrup, through Copenhagen, Denmark, there are four tracks; two are for the separated S-trains and two for mainline trains. Also between Høje Taastrup and Roskilde, where the two center tracks are for InterCity, long distance commuter trains (further than Roskilde or Ringsted), while the outer two tracks are for commuter trains to/from Ringsted or Holbæk.
- The İstanbul–Ankara Main Line has a quadruple track section between Etimesgut and Kızılay in Ankara, Turkey.
- Most of the railway through Stockholm County, Sweden has four tracks, sometimes having two routes. Still the central section has two tracks only, with two more under construction (Stockholm City Line).
- The Amsterdam–Arnhem railway between Amsterdam Bijlmer and Utrecht Centraal, the Netherlands, has been quadrupled between 1999 and 2008.
- The Breda–Eindhoven railway between Boxtel and Eindhoven, the Netherlands, was quadrupled between 1998 and 2002.
- The Rome–Naples high-speed railway and the Rome–Sulmona–Pescara railway in Italy combine to form a quadruple track section between Roma Prenestina railway station and Salone railway station.
- The main section of Ferrovie Nord Milano line between Milan and Saronno in Italy. Outer regional trains are segregated from the inner suburban trains.
- The 112 km long Hamm–Minden railway between Hamm and Minden in Germany is completely quadruple-track with separate tracks for freight and passenger trains.
- The 50 km long railroad from Rastatt to Offenburg in Germany has four tracks. An extension to the Swiss border is under construction, having the new tracks separate for part of the distance, but mostly bundled.
- The 120 km long railroad from Zürich to Berne contains long quadrupel track sections
(All high-speed new lines that have different stations don't qualify here)
- The Guangzhou–Shenzhen Railway is quadruplicated in 2007 for its entire length separating passenger (upgraded high-speed) with freight (and conventional passenger) traffic. It is the first railway in China to do so. (The third track was added in 2000, when conventional track use only 1 track and have to run at high-speed track at some times, causing disruption in schedules, so the fourth track is built.)
- The Beijing-Guangzhou-Shenzhen-Hong Kong High-speed railway have different routes and stations.
- The Shanghai–Nanjing Intercity Railway runs parallel to the slower conventional Nanjing-Shanghai Railway and share many stations for most of its length, effectively making it a 4-track corridor a majority of its length.
- The Beijing-Shanghai High-speed railway have different routes and (with a few exceptions) stations.
- The Jiaozhou-Jinan Passenger-Dominated Line runs parallel to the slower conventional Jiaozhou-Jinan Railway and share many stations for most of its length, and are formally called JiaoJi (Passenger-Dominated) Line when describing train routes, effectively treating JiaoJi line as quadruple track.
- The Jiaozhou-Jinan High-speed railway (not to be confused with the above) is in long-term planning and have different routes and (with a few exceptions) stations.
- Beijing-Kowloon Railway (Nanchang-Jiujiang section) / Nanchang-Jiujiang Intercity Railway. Conventional long-distance trains run on both, and the two lines share all its stations.
- Hunan-Guangxi Railway (Hengyang-Liuzhou section)
- The Tung Chung Line and the Airport Express in Hong Kong are quadruplicated between Kowloon and Tsing Yi stations since 2003, but share two tracks on the rest of their routes (until they diverge again before the western end). The two lines shared two tracks when they were opened in 1998 with separate platforms at stations. In addition, the West Rail runs largely parallel to the Tung Chung Line and the Airport Express throughout Kowloon and New Kowloon, meaning six tracks running side-by-side.
- The Ocean Park Cable Car system has two pairs of ropeways.
- Hankyu Railway in Osaka has a sextuplicated section between Umeda and Juso stations (2.4 km).
- Keihan Main Line in Osaka is quadruplicated between Temmabashi and Neyagawa Signal Box (~13 km).
- Seibu Ikebukuro Line in Tokyo is quadruplicated between Nerima to Nerima-Takanodai stations (3.5 km).
- Between Tokyo and Odawara (JR East) 83.9 km is paired by use (not including Shinkansen).
- Tokyo – Shinagawa 6.8 km: 6 tracks (8 if include Sobu-Yokosuka Line Underground)
- Shinagawa – Tsurumi 14.9 km: 4 tracks
- Tsurumi – Yokohama 7.1 km: 6 tracks
- Yokohama – Totsuka 12.1 km: 4 tracks
- Totsuka – Ofuna 5.6 km: 6 tracks
- Ofuna – Odawara 37.4 km: 4 tracks
- Between Tokyo and Omiya (JR East) is paired by use (not including Shinkansen)
- Tokyo – Akihabara: 6 tracks
- Akihabara – Ueno: 6 tracks
- (Tokyo – Ueno 3.6 km)
- Ueno – Nippori 2.2 km: 10 tracks (2 for Ueno Depot)
- Nippori – Tabata: 4 tracks
- Nippori – Oku: 4 tracks
- Tabata – Akabane: 4 tracks
- Oku – Akabane: 2 tracks
- (Nippori – Akabane 7.4 km)
- Akabane – Omiya 17.1 km: 6 tracks
- Between Kusatsu and Nishi-Akashi (JR West) 120.9 km (not including Shinkansen)
- Kusatsu – Kyoto 22.2 km is paired by direction: 4 tracks
- Kyoto – Umekoji – Mukomachi 6.4 km is paired by direction: 5 tracks
- Mukomachi – Ibaraki 21.8 km is paired by direction: 4 tracks
- Ibaraki – Suita is paired by use: 6 tracks
- Suita – Shin-Osaka is paired by use: 8 tracks
- Shin-Osaka – Osaka – Tsukamoto is paired by direction: 4 tracks
- (Ibaraki – Osaka 14.6 km)
- Shin-Osaka – Miyahara – Tsukamoto: 2 tracks
- Tsukamoto – Hyogo is paired by direction: 4 tracks
- Hyogo – Takatori is paired by direction: 5 tracks
- (Osaka – Takatori 38.2 km)
- Takatori – Nishi-Akashi 17.7 km is paired by use: 4 tracks
- Between Ochanomizu and Mitaka (JR East) 21.5 km is paired by use.
- Ochanomizu – Yoyogi: 4 tracks
- Yoyogi – Shinjuku: 8 tracks
- Shinjuku – Mitaka: 4 tracks
- Between Kinshicho and Chiba (JR East) 34.4 km is paired by use.
- Kinshicho – Nishi-Chiba: 4 tracks
- Nishi-Chiba – Chiba: 6 tracks
- Between Ayase and Toride (JR East) 29.7 km: 4 tracks/paired by use
- Between Osaki and Komagome (JR East) about 20 km is paired by use.
- Osaki – Yoyogi: 4 tracks
- Yoyogi – Shinjuku: 8 tracks
- Shinjuku – Komagome: 4 tracks
- Between Souen and Heiwa (JR Hokkaido) about 9 km
- Souen – Sapporo is paired by use: 3 tracks
- Sapporo – Heiwa is paired by direction: 4 tracks
- Between Niigata and Kami-Nuttari (JR East) 1.9 km: 4 tracks/paired by direction
- Between Imamiya and Tennoji (JR West) 2.2 km: 4 tracks/paired by direction
- Between Inazawa and Nagoya (JR Central) 11.1 km/paired by use: 4 tracks
- Between Hiroshima and Kaitaichi (JR West) 6.4 km: 4 tracks/paired by direction
- Between Orio and Moji (JR Kyushu) 24.6 km
- Orio – Kokura: 4 tracks/paired by use
- Kokura – Higashi-Kokura 1.6 km/paired by direction: 6 tracks
- Higashi-Kokura – Moji is paired by direction: 4 tracks
- Besides JR companies, the following private railway companies in Japan run their own quadruple (or more) tracked sections:
- The Gyeongbu Line in South Korea is quadruplicated on 84.9 km on its route, and sextuplicated on a further 11.7 km
- The Gyeongin Line is quadraple track line, except 1.9 km of double track line between Dongincheon Station and Incheon Station.
- NYC&H RR System Map, circa 1876
- New York Central Mileage Chart 1936
- Penn Central Transportation Company Track Chart 1975
- Japan Railfan Magazine (Koyusha) No. 478 p. 36
- Japan Railfan Magazine (Koyusha) No. 478 p. 37
- Japan Railfan Magazine (Koyusha) No. 478 p. 10
- Japan Railfan Magazine (Koyusha) No. 478 p. 14
- Japan Railfan Magazine (Koyusha) No. 478 p. 16
- Japan Railfan Magazine (Koyusha) No. 478 p. 20
- Japan Railfan Magazine (Koyusha) No. 478 p. 22
- Japan Railfan Magazine (Koyusha) No. 478 p. 23
- Japan Railfan Magazine (Koyusha) No. 478 p. 24
- Japan Railfan Magazine (Koyusha) No. 478 p. 25
- Japan Railfan Magazine (Koyusha) No. 478 p. 26
- Japan Railfan Magazine (Koyusha) No. 478 p. 27
- Japan Railfan Magazine (Koyusha) No. 478 p. 28
- Japan Railfan Magazine (Koyusha) No. 478 p. 29