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62-751: The Merivale Bridge is a double track railway bridge crossing the Brisbane River . It crosses the Milton Reach of the river, located in between the Go Between Bridge and the William Jolly Bridge . Exclusively a railway crossing, it is located between the stations of South Brisbane and Roma Street , linking the northern and southern elements of the Queensland Rail City network . The Merivale Bridge

124-550: A spiral . At Saunderton , England, what became the London-to-Birmingham main line of the Great Western Railway in 1909 was initially part of a single-track branch line from Maidenhead . Down trains follow the route of the old branch line, while up trains follow a more gently graded new construction through a tunnel. This scheme avoided the cost of a new double-track tunnel. Directional running

186-459: A "reserve" track that can allow a reduced capacity service to continue if one track is closed. If a single-track line is designed to be used by more than one train at a time, it must have passing loops (also called passing sidings or crossing loops ) at intervals along the line to allow trains running in different directions to pass each other. These consist of short stretches of double track, usually long enough to hold one train. The capacity of

248-416: A double line might have to be shut down to avoid collisions with trains on those adjacent tracks. These are a form of crossing loop, but are long enough to allow trains approaching each other from opposite directions on single-track lines to cross (or pass) each other without reducing speed. In order for passing lanes to operate safely and effectively, trains must be timetabled so that they arrive at and enter

310-526: A horseshoe curve at 1 in 75 gradient, while the shorter downhill track follows the original single track at 1 in 40 grades. A similar arrangement to Frampton could not be adopted between Rydal and Sodwalls on the Main Western railway line because the 1 in 75 uphill track is on the wrong side of the 1 in 40 downhill track, so both tracks follow the 1 in 75 grade. Another example is at Gunning . Between Junee and Marinna, New South Wales , Australia

372-627: A major bottleneck. For Berlin Stadtbahn the two northern tracks are local S-Bahn and the two other for faster trains. The most notable example of quadruple track in the United States, and perhaps the only four-track section of mainline therein, was the Pennsylvania Railroad 's main corridor through the heart of Pennsylvania around the famous Horseshoe Curve . This line is now owned by Norfolk Southern. Other examples include

434-440: A more direct route into the city for Brisbane's southern system suburban trains than the existing route via Corinda . Since 1986 it also has carried the standard gauge line from New South Wales . It was designed by Cameron McNamara Pty Ltd (consulting engineers) and was fabricated and erected by Transfield . The bridge has been recognised with a number of awards. In 1980 it was named the most outstanding engineering project from

496-596: A second tunnel. An exception is the Hoosac Tunnel , which was duplicated by enlarging the bore. To reduce initial costs of a line that is certain to see heavy traffic in the future, a line may be built as single-track but with earthworks and structures designed for ready duplication. An example is the Strathfield to Hamilton line in New South Wales , which was constructed as mainly single-track in

558-624: A single-track line is determined by the number of passing loops. Passing loops may also be used to allow trains heading in the same direction at different speeds to overtake. In some circumstances on some isolated branch lines with a simple shuttle service (such as the Abbey Line in Great Britain or L202 railway in Croatia) a single-track line may work under the "one train working" principle without passing loops, where only one train

620-541: A single-track railway to double track is called duplication or doubling; converting double track to single track is known as singling. A double-track railway operating only a single track is known as single-line working . Kirkby railway station (until 1977) and Ormskirk railway station (until 1970) were double-track railway , when they were converted into single-track railway with cross-platform interchange . Building bike trails on rail corridors has occurred in limited examples; however, developing rail rights of way for

682-565: A third track signalled in both directions, so that two tracks are available in the peak direction during rush hours. Triple track is used in some parts of the New York City Subway and on the Norristown High-Speed Line to add supplemental rush-hour services. The center track, which serves express trains, is signalled in both directions to allow two tracks to be used in the peak direction during rush hours;

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744-412: A third track was opened between Whittingham and Branxton in 2011 and Branxton to Maitland in 2012 to equalize the headway in both directions for heavy coal traffic. Triple track could be a compromise between double-track and quad-track ; such a system was proposed south of Stockholm Central Station , but was cancelled in favor of Citybanan . In Melbourne and Brisbane several double track lines have

806-421: Is allowed on the line at a time. On single-track lines with passing loops, measures must be taken to ensure that only one train in one direction can use a stretch of single track at a time, as head-on collisions are a particular risk. Some form of signalling system is required. In traditional British practice (and countries using British practice), single-track lines were operated using a token system where

868-415: Is an example of a duplication line that was reduced to single-track in most locations, but has since undergone re-duplication in many places between Baltimore and Philadelphia when CSX increased freight schedules in the late 1990s. Also: Some lines are built as single-track with provision for duplication, but the duplication is never carried out. Examples are: When the capacity of a double-track railway

930-979: Is called duplication or doubling , unless the expansion is to restore what was previously double track, in which case it is called redoubling . The strongest evidence that a line was built as single-track and duplicated at a later date consists of major structures such as bridges and tunnels that are twinned. One example is the twin Slade tunnels on the Ilfracombe Branch Line in the UK. Twinned structures may be identical in appearance, or like some tunnels between Adelaide and Belair in South Australia , substantially different in appearance, being built to different structure gauges . Tunnels are confined spaces and are difficult to duplicate while trains keep on running. Generally they are duplicated by building

992-551: Is in excess of requirements, the two tracks may be reduced to one, in order to reduce maintenance costs and property taxes. In some countries this is called singling . Notable examples of this in the United Kingdom occurred on the Oxford–Worcester–Hereford, Princes Risborough–Banbury and Salisbury–Exeter main lines during the 1970s and 1980s. In all these cases, increases in traffic from the late 1990s have led to

1054-515: Is quadruple tracked in most portions south of New Haven, but also has a few triple-track segments. The Metra Electric District is quadruple-tracked on most of the main line north of Kensington/115th Street station , with local trains running in the center two tracks, and express trains on the outer two tracks. Outside the United States the Chūō Main Line is an example of a modern, heavily utilized urban quadruple track railway. Quadruple track

1116-661: Is the only inner-city rail crossing in Brisbane. By 2016 it was expected to be over capacity, leading the Queensland Government to announce the Cross River Rail project. The Merivale Bridge opened on 18 November 1978 by Premier Joh Bjelke-Petersen . At the opening with 850 guests, the Premier, described the occasion as "the start of the second stage in the history of Queensland Railways". It formed

1178-557: Is two separate lines operationally combined to act as a double-track line by converting each line to unidirectional traffic. An example is in central Nevada , where the Western Pacific and Southern Pacific Railroads , longtime rivals who each built and operated tracks between northern California and Utah , agreed to share their lines between meeting points near Winnemucca and Wells , a distance of approximately 180 miles (290 km). Westbound trains from both companies used

1240-602: Is used in rapid transit systems as well: throughout the New York City Subway , the Chicago "L" 's North Side Main Line , and SEPTA 's Broad Street Line in the United States, and on the London Underground in the United Kingdom. The two tracks of a double-track railway do not have to follow the same alignment if the terrain is difficult. At Frampton, New South Wales , Australia, the uphill track follows something of

1302-538: The California Zephyr along these routes. Single-track railway Single track is significantly cheaper to build and maintain, but has operational and safety disadvantages. For example, a single-track line that takes 15 minutes to travel through would have capacity for only two trains per hour in each direction safely. By contrast, a double track with signal boxes four minutes apart can allow up to 15 trains per hour in each direction safely, provided all

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1364-681: The Boyne Viaduct , a bridge just north of Drogheda railway station in Ireland ). The bridge over the Murray River between Albury and Wodonga is double-track, but because of insufficient strength in the bridge only one train is allowed on it at a time. The bridge has since been singled as part of the North East Line Standardisation with the old broad gauge track now disconnected but remains in place on

1426-558: The Canadian National main line in the Greater Toronto Area and Southern Ontario are triple track to facilitate high traffic density of freight services, intercity , and suburban passenger trains sharing the same lines. India, through its state-owned Indian Railways, has initiated the construction of a third track between Jhansi and Nagpur via Bhopal (approximately 590 kilometres (370 miles)) for reducing

1488-584: The Hudson and New Haven Lines, both of which are shared between Metro-North and Amtrak in New York and Connecticut. The New Haven Line is quadruple track along its entire length, while the Hudson Line is only quadruple tracked along the shared portion from Riverdale to Croton–Harmon and along the shared track from Grand Central Terminal to Yankees–East 153rd Street . Amtrak 's Northeast Corridor

1550-672: The Main Western Railway between Wallerawang and Tarana , and between Gresham and Newbridge were singled in the 1990s. A new passing loop was opened on part of the closed track at Rydal in the Wallerawang–Tarana section during 2019. A double-track tunnel with restricted clearances is sometimes singled to form a single track tunnel with more generous clearances, such as the Connaught Tunnel in Canada or

1612-426: The 1880s, with full duplication completed around 1910. All bridges, tunnels, stations, and earthworks were built for double track. Stations with platforms with 11-foot (3.4 m) centres had to be widened later to 12-foot (3.7 m) centres, except for Gosford . The former Baltimore and Ohio Railroad (B&O) line between Baltimore and Jersey City , now owned by CSX and Conrail Shared Assets Operations ,

1674-655: The Association of Consulting Engineers of Australia. Judges appreciated the combination of aesthetics and functionality. It also won the 1979 Steel Award. It had taken almost a century to get Brisbane's north and south rail networks joined by a bridge over the Brisbane River . As far back as 1885, the then Engineer-in-Chief for the Southern Division Railways arranged for the trial rail survey being done in South Brisbane to be extended across

1736-473: The Netherlands as NS Class 1600 , the driving cab was not completely redesigned, keeping the driver on the left even though trains use the right-hand track in the Netherlands. Generally, the left/right principle in a country is followed mostly on double track. On steam trains, the steam boiler often obscured some of the view, so the driver was preferably placed nearest to the side of the railway, so that it

1798-734: The Southern Pacific's Overland Route , and eastbound trains used the Western Pacific's Feather River Route (now called the Central Corridor ). Crossovers were constructed where the lines ran in close proximity to allow reverse movements. This was necessary as while for most of this run the tracks straddle opposite sides of the Humboldt River , at points the two tracks are several miles apart and some destinations and branch lines can only be accessed from one of

1860-551: The Tickhole Tunnel in New South Wales , Australia. In the case of the Tickhole Tunnel a new single-track tunnel was built and the two tracks in the original tunnel were replaced by one track in the centreline of the tunnel. Another case where this was necessary was the Hastings Line in the United Kingdom, where the tunnels were eventually singled to permit the passage of standard British-gauge rolling stock. Before

1922-588: The bridge. Railways that become especially busy in wartime and are duplicated, especially in World War I, may revert to single track when peace returns and the extra capacity is no longer required. The Flanders campaign saw duplication of the Hazebrouck – Ypres line, amongst other works. Severe gradients can make the headway in the uphill direction much worse than the headway in the downhill direction. Between Whittingham and Maitland, New South Wales ,

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1984-528: The broad gauge declined, the lines were converted to bi-directional double track 1,435 mm ( 4 ft  8 + 1 ⁄ 2  in ) gauge lines. Quadruple track consists of four parallel tracks. On a quad-track line, faster trains can overtake slower ones. Quadruple track is mostly used when there are "local" trains that stop often (or slow freight trains), and also faster inter-city or high-speed "express" trains. It can also be used in commuter rail or rapid transit . The layout can vary, often with

2046-447: The construction of the bridge, as well as documents and research papers relating to the bridge Double track A double-track railway usually involves running one track in each direction, compared to a single-track railway where trains in both directions share the same track. In the earliest days of railways in the United Kingdom, most lines were built as double-track because of the difficulty of co-ordinating operations before

2108-448: The crossing loop is long enough to hold several trains, and to allow opposing trains to cross without slowing down or stopping, then that may be regarded as double-track. A more modern British term for such a layout is an extended loop. The distance between the tracks' centres makes a difference in cost and performance of a double-track line. The track centres can be as closely spaced and as cheap as possible, but maintenance must be done on

2170-487: The development of the telegraph and the train order system. In any given country, rail traffic generally runs to one side of a double-track line, not always the same side as road traffic. Thus in Belgium, China, France (apart from the classic lines of the former German Alsace and Lorraine), Sweden (apart from Malmö and further south), Switzerland, Italy and Portugal for example, the railways use left-hand running, while

2232-498: The different tracks is called the "six foot". It is not safe to stand in the gap between the tracks when trains pass by on both lines, as happened in the Bere Ferrers accident of 1917. When one track of a double-track railway is out of service for maintenance or a train breaks down, all trains may be concentrated on the one usable track. There may be bi-directional signalling and suitable crossovers to enable trains to move onto

2294-485: The early days of railways in North America it was common to rely upon simple timetable operation where operators knew where a train was scheduled to be at a particular time, and so would not enter a single-track stretch when they were not scheduled to. This generally worked but was inflexible and inefficient. It was improved with the invention of the telegraph and the ability to issue train orders . Converting

2356-509: The invention of the telegraph . The lines also tended to be busy enough to be beyond the capacity of a single track. In the early days the Board of Trade did not consider any single-track railway line to be complete. In the earliest days of railways in the United States most lines were built as single-track for reasons of cost, and very inefficient timetable working systems were used to prevent head-on collisions on single lines. This improved with

2418-540: The issue was raised in connection with proposals to electrify the Brisbane suburban network. Surveys and plans were finalised in 1954, and in 1955 the State Government announced its decision to proceed with the construction and initiated land resumptions. However, financial constraints again caused a deferment. This study was submitted to the Government in 1970. It recommended that the crossing should follow

2480-490: The length and width of trains is contingent on the minimum railway curve radius of the railway. Increasing the width of track centres of 6 metres (20 ft) or more makes it much easier to mount signals and overhead wiring structures. Very widely spaced centres at major bridges can have military value. It also makes it harder for rogue ships and barges to knock out both bridges in the same accident. Railway lines in desert areas affected by sand dunes are sometimes built with

2542-423: The lines. There is a grade separated crossover of the two lines in the shared track area near Palisade, Nevada , which results in trains following right hand traffic in the eastern half of the shared track area, but left hand traffic in the western half. The Union Pacific Railroad has since acquired both of these lines, and continues to operate them as separate lines using directional running. Amtrak also runs

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2604-539: The local train stations, the express trains can pass through the station at full speed. For example on the Nuremberg-Bamberg railway , which is quadruple track for most of its course, the inner two tracks are used by the S-Bahn Nuremberg whereas the outer tracks are used for regional express and Intercity Express trains. The section in northern Fürth where the line is "only" double track creates

2666-560: The loop with close time tolerances, otherwise they will need to slow or even be brought to a complete stop to allow the oncoming train to pass. They are suited to lines with light to moderate traffic. An example of where passing lanes have been installed in order to improve travel times and increase line capacity is the 160-kilometre (100-mile) section of the Main Southern railway line in Australia between Junee and Albury . This

2728-537: The opening with 850 guests, the Premier, described the occasion as "the start of the second stage in the history of Queensland Railways". The first train to use the train was Diesel electric locomotive no. 2422. The bridge was named after Merivale Street in South Brisbane with which the bridge is aligned. The bridge was refurbished in 2016. State Library of Queensland holds John Christsen Merivale Bridge collection which contains 370 chronological photographs of

2790-666: The other track expeditiously (such as the Channel Tunnel ), or there may be some kind of manual safeworking to control trains on what is now a section of single track. See single-line working . Accidents can occur if the temporary safeworking system is not implemented properly, as in: From time to time, railways are asked to transport exceptional loads such as massive electrical transformers that are too tall, too wide or too heavy to operate normally. Special measures must be carefully taken to plan successful and safe operation of out-of-gauge trains . For example, adjacent tracks of

2852-442: The outer tracks use bi-directional running and serve local trains exclusively in one direction. During service disruptions on one of the two outer tracks, trains could also bypass the affected sections on the center track. The Union Pacific Railroad mainline through Nebraska has a 108-mile (174 km) stretch of triple track between North Platte and Gibbon Junction, due to a high traffic density of 150 trains per day. Portions of

2914-727: The partial reinstatement of double track. In New Zealand the Melling Line was singled to the Western Hutt Railway Station in Lower Hutt in 1958 after it became a branch line rather than part of the main Hutt Valley Line . Kirkby railway station (until 1977) and Ormskirk railway station (until 1970) were double-track railway, when they were converted into single-track railway with cross-platform interchange . In New South Wales, Australia,

2976-431: The river to the main western line near Countess Street. In 1889, he arranged to have levels taken for alternative routes to Roma Street tunnel via Herschel Street, and to Central station via a direct route between Turbot and Ann Streets. The Herschel Street route was recommended for adoption, and plans subsequently prepared. However the government decided not to proceed and requested an alternative survey, but that too

3038-491: The roads use right-hand running. However, there are many exceptions: Handedness of traffic can affect locomotive design. For the driver, visibility is usually good from both sides of the driving cab, so the choice of which side the driver should sit is less important. For example, the French SNCF Class BB 7200 is designed to use the left-hand track and therefore uses LHD. When the design was modified for use in

3100-478: The route, as surveyed in 1890. The Queensland State Cabinet approved the bridge in October 1971. In 1975, a contract was let to Transfield for the construction of the bridge and the line into South Brisbane station . The first pile was driven on 21 August 1975. The bridge took a period of three years and three months to be built. The Merivale Bridge opened on 18 November 1978 by Premier Joh Bjelke-Petersen . At

3162-438: The side. Signals for bi-directional working cannot be mounted between the tracks, so they must be mounted on the 'wrong' side of the line or on expensive signal bridges . For standard gauge tracks the distance may be 4 metres (13 ft) or less. Track centres are usually further apart on high speed lines, as pressure waves knock each other as high-speed trains pass. Track centres are also usually further apart on sharp curves, and

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3224-510: The signals and points (UK term) or rail switches (US) are power-operated, it can be worthwhile to provide signals for each line which cater for movement in either direction, so that the double line becomes a pair of single lines. This allows trains to use one track where the other track is out of service due to track maintenance work, or a train failure, or for a fast train to overtake a slow train. Most crossing loops are not regarded as double-track even though they consist of multiple tracks. If

3286-556: The singling, narrow-bodied stock, specially constructed for the line, had to be used. As part of the Regional Fast Rail project in Victoria, Australia , the rail line between Kyneton and Bendigo was converted from double- to single-track to provide additional clearance through tunnels and under bridges for trains travelling at up to 160 km/h (99 mph). A similar process can be followed on narrow bridges (like

3348-400: The traffic load and delays in passenger train arrivals. The construction between Bina and Bhopal and between Itarsi and Budhni had been completed by April 2020. The Melbourne to Albury railway originally consisted of separate 1,600 mm ( 5 ft 3 in ) gauge and 1,435 mm ( 4 ft  8 + 1 ⁄ 2  in ) gauge single track lines, but when traffic on

3410-594: The train driver had to be in possession of a token in order to enter a stretch of single track. Because there was only one unique token issued at any one time for each stretch of single track, it was impossible for more than one train to be on it at a time. This method is still used on some minor lines but in the longest single-track lines in Britain (e.g. the Highlands of Scotland) this has been superseded by radio communication, known as Radio Electronic Token Block . In

3472-424: The trains travel at the same speed. This hindrance on the capacity of a single track may be partly overcome by making the track one-way on alternate days. Long freight trains are a problem if the passing stretches are not long enough. Other disadvantages include the propagation of delays, since one delayed train on a single track will also delay any train waiting for it to pass. Also, a single track does not have

3534-419: The two outer tracks carrying the local trains that stop at every station so one side of stations can be reached without staircase; this can also be reversed, with express trains on the outside and locals on the inside, for example if staffed ticket booths are wanted, allowing one person for both directions. At other places two tracks on one half of the railway carry local trains and the other half faster trains. At

3596-489: The two tracks are at different levels, with the original southbound and downhill track following ground level with a steep gradient, while the newer northbound and uphill track has a gentler gradient at the cost of more cut and fill . At the Bethungra Spiral , Australia, the downhill track follows the original short and steep alignment, while the uphill track follows a longer, more easily graded alignment including

3658-404: The two tracks separated, so that if one is covered by sand, the other(s) are still serviceable. If the standard track centre is changed, it can take a very long time for most or all tracks to be brought into line. On British lines, the space between the two running rails of a single railway track is called the "four foot" (owing to it being 'four foot something' in width), while the space between

3720-410: Was built as a single track line in stages between 1878 and 1881, and was partially duplicated between 2005 and 2010 by the construction of four passing lanes each 6 km (4 mi) long. In this instance, this was accomplished by extending pre-existing crossing loops of either 900 metres (3,000 ft) or 1,500 metres (4,900 ft) in length. The process of expanding a single track to double track

3782-401: Was easier to see the signals. On single track, when trains meet, the train that does not stop often uses the straight path in the turnout, which can be left or right. Double-track railways, especially older ones, may use each track exclusively in one direction. This arrangement simplifies the signalling systems, especially where the signalling is mechanical (e.g. semaphore signals ). Where

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3844-400: Was held over. Worried at losing trade to central city businesses, the merchants of South Brisbane fought against the bridge. In 1913, the then Premier requested that plans for a direct route through Ann Street to Albert Square (now King George Square ) be put in hand. In 1919, the matter was raised again, but after further pressure from antilobbyists, was once more allowed to lapse. In 1950,

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