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. A single track Railway is one where traffic in both directions shares the same track
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Overview
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 prior to the invention of the telegraph. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Also the lines tended to be busy enough to be beyond the capacity of single track anyway.
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 employed to prevent head-on collisions on single lines. The United States of America —commonly referred to as the This improved with the development of the telegraph and the train order system. Train order operation is a system by which the railroads of North America conveyed operating instructions before the days of Centralized traffic control, Direct
Operation
Handedness
In any given country, rail traffic generally runs to one side of a double track line, which is not necessarily the same side that road vehicles in the same country keep to. Right-hand traffic and left-hand traffic mean regulations requiring all traffic to keep either to the left or the right side of the Road. Thus in Belgium, China, France (apart from the former German Alsace and Lorraine), Sweden, Switzerland and Italy for example, the railways use left hand running, while the roads use right hand running. The Kingdom of Belgium is a Country in northwest Europe. It is a founding member of the European Union and hosts its headquarters as well as those China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National This article is about the country For a topic outline on this subject see List of basic France topics. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest
Where the French railways which use left hand running meet the German railways which use right hand running, flyovers are provided to convert from one hand to the other. An overpass (called a flyover in the UK and most Commonwealth countries is a Bridge, Road, Railway or
Many countries do not have a great amount of double track, and the border crossing are usually single track, so the question is moot.
Bi-directional running
Double track railways, especially older ones, use each track exclusively in one direction. This simplifies the signalling systems, especially where the signalling is mechanical.
Where the signals and points are power operated, it can be worthwhile to signal each line in both directions, 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. See single-line working for a discussion of this topic. On a Double track Railway, single-line working refers to the practice of using one track out of two usually when one of the tracks is out of use for maintenance or
Crossing loops
Crossing loops, while consisting of two or more tracks, are not normally regarded as double track. A passing loop (or "crossing loop" is a place on a single line railway/tramway where trains/trams in opposing directions can pass each other If 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.
Passing lanes
The upgrade project between Junee in New South Wales and Melbourne is to build 19 so-called passing lanes which are loops 7km long which are able to hold up to 3 trains 1800m long. Junee is a small town in the Riverina region of New South Wales, Australia. Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3
Track centres
The distance between the track centres makes a difference in cost and performance of a double track line. The track centres can be as narrow and as cheap as possible, but this precludes maintenance workers standing safely between the lines. Signals for bi-directional working cannot be mounted between the tracks so must be mounted on the 'wrong' side of the line or on expensive signal bridges. Very narrow track centres are also undesirable for high speeds, as pressure waves knock each other as high speed trains pass.
Narrow track centres might be 4m or less. Narrow track centres may have to be widened on sharp curves to allow for long rail vehicles following the arc of the curve, and this increases the work load for the surveyor. If the track centres are increased to 5m or so, this suits high speed trains passing each other, and eliminates the need to widen the centres on sharp curves. If the track centres are increased to 6m or so, signals and overhead wiring structures can always be mounted on the ground.
Very wide centres at major bridges can have military value. It also makes it harder for rogue ships and barges knocking out both bridges in the same accident.
Railway lines in desert areas affected by sand dunes are sometimes built on alternate routes so that if one is covered by sand, the other(s) are still serviceable.
Temporary single track
When one track of a double track railway is out of service for maintenance or a train break down, all trains may be concentrated on the one good track. There may be bi-directional signalling and suitable crossovers to enable trains to move onto the other track expeditiously (see, for example, the article on the Channel Tunnel), or there may be some kind of manual safeworking to control trains on what is now a section of single track. The Channel Tunnel (Le tunnel sous la Manche also known as the Chunnel, is a undersea rail tunnel linking Folkestone, Kent in England with A single track Railway is one where traffic in both directions shares the same track See single-line working for a discussion of this topic. On a Double track Railway, single-line working refers to the practice of using one track out of two usually when one of the tracks is out of use for maintenance or
Accidents can occur if the temporary safeworking system is not implemented properly:
Bruehl train disaster - 2000. In the Brühl train disaster on 6 February 2000, a train negotiated a low speed turnout at three times the correct speed and derailed killing 8 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. 
2006 Zoufftgen rail crash
Passing lanes
To improve travel times and increase line capacity the 300km of line between Junee and Melbourne is to partially duplicated in a configuration called Passing lanes. The Zoufftgen rail crash occurred on October 11, 2006, near Zoufftgen, Moselle, France, close to Metz and the border with Junee is a small town in the Riverina region of New South Wales, Australia. Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3 Existing crossing loops are mostly 900m and 1500m long, and these will be enhanced by loops 6000m long which are long enough to be regarded as nearly double track.
Construction
Duplication
The process of expanding a single track to double track is called duplication or doubling. A single track Railway is one where traffic in both directions shares the same track
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 line in the United Kingdom. History On 20 July 1874 a railway link was opened between Barnstaple and Ilfracombe The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Twinned structure may be identical in appearance, or like some tunnels between Adelaide and Belair South Australia, substantially different in appearance. Adelaide is the capital and most populous city of the Australian state of South Australia, and is the fifth largest city in Australia with a South Australia is a state of Australia in the southern central part of the country
Tunnel Duplication
Tunnels are confined spaces and are difficult to duplicate while trains keep on running. Generally they are duplicated by building a second tunnel. An exception would be the Hoosac Tunnel which was duplicated by enlarging the bore. The Hoosac Tunnel (also called Hoosic or Hoosick Tunnel) is a 4
Provision for duplication
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 Australia which was constructed as mainly single track in the 1880s, with full duplication only completed around 1910. Strathfield is an Inner West Suburb of Sydney, in the state of New South Wales, Australia. Hamilton is a railway station located in Hamilton, a suburb of Newcastle, New South Wales, Australia. For a topic outline on this subject see List of basic Australia topics. All bridges, tunnels, stations, and earthworks were built for double track. The former B & O Railroad Washington-Jersey City line now under CSX ownership is an example of a duplication line that was reduced to single track in most locations, but has since undergone duplication in many places between Baltimore, Maryland and Philadelphia, Pennsylvania when CSX increased freight schedules in the late 1990's. The Baltimore and Ohio Railroad ( B&O) was one of the Oldest railroads in the United States and the first Common carrier railroad Philadelphia (ˌfɪləˈdɛlfiə
Never used provision for duplication
Some lines are built as single track with provision for duplication, but the duplication is never carried out. Examples include:
- Bluebell Railway: Horsted Keynes to Lewes. The Bluebell Railway is a heritage line running for nine miles along the border between East Sussex and West Sussex, England. Horsted Keynes is a village and Civil parish in the Mid Sussex District of West Sussex, England. Lewes (ˈluːɨs Lewis) is the County town of East Sussex, England and gives its name to the Local government district in which it
- Keighley and Worth Valley Railway - including bridge and tunnels and a deviation. The Keighley and Worth Valley Railway is a five-mile (eight-km long Heritage railway line in West Yorkshire, England, that runs from Keighley
- Westerham in Kent. History Authorisation for the construction of the line was obtained in 1864, 1867 and 1870 by the South Eastern Railway (SER KENT (1400 AM) is a Radio station broadcasting a Adult Standards/MOR format
- Monkerei Tunnel in New South Wales - double track size at summit reduces fume problem in tunnel.
- Golgotha Tunnel near Eythorne on East Kent Light Railway was only partly excavated for the second track. Eythorne is a Civil parish and small Village of about 2000 homes located 6 The East Kent Light Railway was part of the Colonel Stephens group of cheaply-built rural light railways in England
Singling
When the capacity of a double track railway is in excess of requirements, the two tracks may be reduced to one. In some countries this is called singling.
Tunnel singling
A double track tunnel with restricted clearances is sometimes singled to form a single track tunnel with generous clearances, such as the Connaught Tunnel in Canada or the Tickhole Tunnel in New South Wales, Australia. Connaught Tunnel, in the Selkirk Mountains under Rogers Pass on the Canadian Pacific Railway main line between Calgary Alberta, and Revelstoke Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page For a topic outline on this subject see List of basic Australia topics. 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. A notorious 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 (prior to the singling, narrow bodied stock was used, specially constructed for the line). The Hastings Line is a railway line in Kent and East Sussex linking Hastings with the main town of Tunbridge Wells, and from there into
A similar process can be followed on narrow bridges (like the bridge north of Drogheda railway station in Ireland). Drogheda railway station (MacBride Station serves Drogheda in County Louth, Ireland. Ireland ( Irish: Éire, ˈeːrʲə is a country in north-western Europe.
Other tunnel singling
Oddities
Non-parallel double track
The two tracks of a double track railway do not have to follow the same alignment if the terrain is difficult. The Hoosac Tunnel (also called Hoosic or Hoosick Tunnel) is a 4 At Frampton, New South Wales, Australia the uphill track follows something of a horseshoe curve at 1 in 75 gradient, while the shorter downhill track follows the original single track at 1 in 40 grades. Frampton is a locality on the Sydney to Melbourne rail line and in the north east part of the Riverina and situated about 14 kilometres south west from Cootamundra For a topic outline on this subject see List of basic Australia topics. Between Junee and Marina, New South Wales, Australia 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 having a gentler gradient at the cost of more cut and fill. Junee is a small town in the Riverina region of New South Wales, Australia. For a topic outline on this subject see List of basic Australia topics. Cut and Fill in earthmoving is the process of constructing a Railway, Road or Canal whereby the amount of material from cuts roughly matches
At Bethungra, the downhill track follows the original short and steep alignment, while the uphill track follows a longer, more easily graded alignment including a spiral. Bethungra is a small town in Junee Shire in the South West Slopes region of New South Wales, Australia situated on the Olympic Way A spiral (sometimes called a spiral loop or just loop) is a technique employed by Railways to ascend steep hills
Split ownership
An unusual stretch of double track in the west of the United States actually comprises two separate single track lines owned by separate companies. The United States of America —commonly referred to as the A single track Railway is one where traffic in both directions shares the same track However, the capacity of the two tracks is greatly increased if they are combined and operated as if they were a double track line, and this indeed is what the two companies do. Canadian Pacific and Canadian National are starting to do the same. The Canadian Pacific Railway ( Another example was in Conshohocken, Pennsylvania where the former Reading Railroad and Pennsylvania Railroad shared lines, and even overhead electrical wire supports, for a 2-mile stretch on the northern bank of the Schyulkill River. Conshohocken is a borough on the Schuylkill River in Montgomery County Pennsylvania, in suburban Philadelphia. The Reading Company, usually called the Reading Railroad ( and officially known as the Philadelphia and Reading Rail Road and then the Philadelphia and The Pennsylvania Railroad was an American Railroad, founded in 1846 Both lines eventually came under Conrail ownership in 1976 with the former PRR line being abandoned and now used as a hike/bike path. Consolidated Rail Corporation, also known as Conrail, began operations on April 1, 1976 as a federally funded takeover of the major railroad
Mixing double and single track
Because double and single track may use different signalling systems it may be awkward and confusing to mix double and single track too often. For example, intermediate mechanical signal boxes on a double track line can be closed during periods of light traffic, but this cannot be done if there is a single line section in between. This problem is less serious with electrical signalling such as Centralized traffic control. Centralized traffic control ( CTC) is a signalling system used by Railroads The system consists of a centralized Train dispatcher 's office
References
- ^ Railway Masterpieces by Brian Solomon ISBN 0-87349-323-0 p122
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