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:
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.
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.
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 Northern 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.
Two double track lines along opposite sides of a river can operate as a quadruple track. Examples of this can be found in Rhone in France and Rhine in Germany.
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.
Several lines radiating from Brussels are quadrupled, for instance the Ghent-Ostend line as far as Essene-Lombeek. Further quadrupling has recently been carried out as part of the development of the Brussels Regional Express Network. The building of high-speed lines has also led to quadrupling - for instance the HSL 2 high-speed line between Brussels and Cologne runs inside the local lines as far as Leuven. Meanwhile since 1934 Brussels and Antwerp have been connected by two separate pairs of double track. Fast trains normally use line 25, while line 27 serves slow trains. In places they run parallel, but at times diverge and cross over each other.
- The Berlin Stadtbahn, Germany, has four tracks. Two are for the separated S-Bahn and two for mainline 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 railway from Rastatt to Offenburg in Germany has four tracks.
- The Hohenzollern Bridge, with six tracks
- The line from Munich to Augsburg has four tracks and near Munich even more
- 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.
- All of the mainline railway through Stockholm County (between Järna and north of Märsta, 83 km (52 mi)) has four tracks, sometimes having two routes. There are plans to widen Stockholm–Bålsta; north of Märsta–Uppsala and Malmö–Lund to quadruple track with parts finished or under construction. After this, the Stockholm commuter rail would have its own tracks everywhere.
- The 120 km long railway from Zürich to Olten contains long quadruple track sections from Zürich to Killwangen-Spreitenbach and from Rupperswil to Aarau, currently being extend to Olten.
- 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.
- The Metro-North Railroad's New Haven Line is four-tracked from Grand Central Terminal in New York City to New Haven Union Station in New Haven, Connecticut.
- Much of Amtrak's Northeast Corridor from Washington, D.C., to New Haven, Connecticut, is a four-track line, except for the segment between New Rochelle and the Sunnyside Yard in Queens, New York. In the Bronx, the Amtrak trains run separate from the New Haven Line. The right-of-way from Woodside, Queens, over the Hell Gate Bridge to Co-op City, Bronx, is three-tracked due to the presence of the single-tracked New York Connecting Railroad.
- 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 Rail Road's Main Line is four-tracked from its East River Tunnels portal in Long Island City to Queens Village, 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 North Side Main Line (Purple, Red, and Brown Lines) between Howard and Fullerton.
- The Metra Electric District Line main line in Chicago is quadrupled between 11th street and 111th street.
- 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.
- Market Street in San Francisco had quadruple track streetcars for much of its length in the early 1900s – two tracks operated by United Railroads of San Francisco and two tracks operated by the San Francisco Municipal Railway (Muni). As the streetcar system was acquired by the government and was modernized to light rail, capacity was maintained by tunneling an additional right-of-way for Muni vehicles parallel, under the surface. The Market Street Subway's two subterranean levels are both double tracked, and the (retained) double tracked surface section runs heritage trolley cars for a total of six tracks in the same thoroughfare. The surface and upper level are laid at standard gauge and maintained by the San Francisco Municipal Transportation Agency while the lower level is Indian gauge track operated by Bay Area Rapid Transit.
- Bay Area Rapid Transit had plans that called for Market Street Subway to be fully quadruple tracked, with express trains running on a separate level than local trains; the final system was configured due to budget constraints.
- Reading Company's New York Branch between Neshaminy Falls and Yardley station was originally quadruple-tracked before being reduced to three tracks between Neshaminy Falls and Woodbourne station and two tracks between Woodbourne and Yardley. In 2016, the third track between Woodbourne and Yardley was relaid by SEPTA in order to separate SEPTA's West Trenton Line and CSX's Trenton Subdivision.
- 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
- 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: