Double track
Encyclopedia
Single track (rail)
A single track railway is where trains in both directions share the same track. Single track is normally used on lesser used rail lines, often branch lines, where the traffic density is not high enough to justify the cost of building double tracks....
railway where trains in both directions share the same track.
Overview
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, most lines were built as double track because of the difficulty of co-ordinating operations prior to the invention of the telegraph. The lines also tended to be busy enough to be beyond the capacity of single track. In the early days the Board of Trade
Board of Trade
The Board of Trade is a committee of the Privy Council of the United Kingdom, originating as a committee of inquiry in the 17th century and evolving gradually into a government department with a diverse range of functions...
did not consider any single track railway line to be complete.
In the earliest days of railways in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
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. This improved with the development of the telegraph and the train order
Train order
Train order operation, or more accurately Timetable and Train order operation, is a largely obsolete system by which the railroads of North America conveyed operating instructions before the days of centralized traffic control, direct traffic control, and the use of track warrants conveyed by radio...
system.
Handedness
In any given country, rail traffic generally runs to one side of a double track line, not always the same as road traffic. Thus in BelgiumBelgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
(apart from the former German Alsace and Lorraine), Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
and Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
for example, the railways use left hand running, while the roads use right hand running.
On the (pre-1918) French-German border, for example, flyover
Overpass
An overpass is a bridge, road, railway or similar structure that crosses over another road or railway...
s are provided so that train moving on the left in France end up on the right in Germany and vice versa.
Bi-directional running
Double track railways, especially older ones, may use each track exclusively in one direction. This arrangement simplifies the signallingRailway signalling
Railway signalling is a system used to control railway traffic safely, essentially to prevent trains from colliding. Being guided by fixed rails, trains are uniquely susceptible to collision; furthermore, trains cannot stop quickly, and frequently operate at speeds that do not enable them to stop...
systems, especially where the signalling is mechanical (e.g., semaphore signals
Railway semaphore signal
One of the earliest forms of fixed railway signal is the semaphore. These signals display their different indications to train drivers by changing the angle of inclination of a pivoted 'arm'. Semaphore signals were patented in the early 1840s by Joseph James Stevens, and soon became the most...
).
Where the signals and points (UK term) or rail switches (US) 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.
Crossing loops
Most crossing loopPassing loop
A passing loop is a place on a single line railway or tramway, often located at a station, where trains or trams in opposing directions can pass each other. Trains/trams in the same direction can also overtake, providing that the signalling arrangement allows it...
s are not regarded as double track even though they consist of multiple tracks. 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.
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 maintenance must be done on the side. 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 4 metres (13.1 ft) 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 a surveyor's workload. Widening a track centre to 5 metres (16.4 ft) or so suits high speed trains passing each other, and eliminates the need to widen the centres on sharp curves. Increasing width of track centres of 6 metres (19.7 ft) or more makes it much easier to mount signals and overhead wiring structures.
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.
Track Centre examples
(put in order of size)- 09' 8.0" (2.94m)
Liverpool and Manchester RailwayLiverpool and Manchester RailwayThe Liverpool and Manchester Railway was the world's first inter-city passenger railway in which all the trains were timetabled and were hauled for most of the distance solely by steam locomotives. The line opened on 15 September 1830 and ran between the cities of Liverpool and Manchester in North...
1830 at opening day; later widened. - ? ? ? ? ? ? ? ? Hastings LineHastings LineThe Hastings Line is a railway line in Kent and East Sussex linking Hastings with the main town of Tunbridge Wells, and from there into London via Sevenoaks.-Openings:The line was opened by the South Eastern Railway in main three stages: – :...
- unusually narrow until tunnel-singled. - 10' 8.5" (3.26m) United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
(a six foot plus a four foot) - 11' 0.0" (3.35m)
New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
1855 old standard (estimated) - 12' 0.0" (3.66m) New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
1910 new standard - 13' 1.5" (4.00m) New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
1973 metric standard - 14' 9.0" (4.50m) Certain ARTCAustralian Rail Track CorporationAustralian Rail Track Corporation is a federal government owned corporation established in 1997 that owns, leases, maintains and controls the majority of main line standard gauge railway lines on the mainland of Australia, known as the Defined Interstate Rail Network .-History:The Interstate...
lines
If the standard track centres is changed, it can of course take a very long time for most or all tracks to be brought into line.
Accidents
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 the different tracks is called the "Six foot" (same reason). It is not safe to stand in the gap between the tracks when trains pass by on both lines, as happened in the Bere FerrersBere Ferrers railway station
Bere Ferrers station on the Tamar Valley Line is situated near the village of Bere Ferrers in Devon. The station is on the former Southern main line between Exeter and Plymouth via Okehampton...
accident of 1917
- Narrow track centres on the Liverpool and Manchester Railway contributed to a fatal accident on opening day.
- A US naval submarine officer, Captain Jacquet, was killed getting out of the wrong side of a train.
- narrow track centres contribute to "Second Train Coming" accidents at level crossingLevel crossingA level crossing occurs where a railway line is intersected by a road or path onone level, without recourse to a bridge or tunnel. It is a type of at-grade intersection. The term also applies when a light rail line with separate right-of-way or reserved track crosses a road in the same fashion...
s since it is harder to see the second train.
Temporary single track
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 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. See single-line workingSingle-line working
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 because of damage or some obstruction.- Circumstances :...
.
Accidents can occur if the temporary safeworking system is not implemented properly:
Bruehl train disaster - 2000. 2006 Zoufftgen rail crash
2006 Zoufftgen rail crash
The 2006 Zoufftgen train collision occurred around 11.45 am on 11 October 2006, near Zoufftgen, Moselle, France, some 20 metres from the border with Luxembourg, on the Metz – Zoufftgen line. Two trains collided head-on while one track of a double track line was out of service for maintenance...
Passing lanes
To improve travel times and increase line capacity the 300 kilometres (186.4 mi) of line between Junee and MelbourneMelbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
is to partially duplicated in a configuration called Passing lane
Passing lane
A passing lane or overtaking lane is the lane on a multi-lane highway or motorway closest to the center of the road ....
s. Existing crossing loops are mostly 900 metres (2,952.8 ft) and 1500 metres (4,921.3 ft) long, and these will be enhanced by loops 6 kilometres (3.7 mi) long which are long enough to be regarded as nearly double track.
Duplication
The process of expanding a single track to double track is called duplication or doubling.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
Ilfracombe Branch Line
The Ilfracombe Branch of the London & South Western Railway , ran between Barnstaple and Ilfracombe in North Devon. The branch opened as a single-track line in 1874, but was sufficiently popular that it needed to be upgraded to double-track in 1889....
line in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. Twinned structure may be identical in appearance, or like some tunnels between Adelaide
Adelaide
Adelaide is the capital city of South Australia and the fifth-largest city in Australia. Adelaide has an estimated population of more than 1.2 million...
and Belair
Belair, South Australia
Belair is a suburb situated in the southern foothills of Adelaide, South Australia.-Geography:A leafy suburb, Belair was established during the settlement of Adelaide as a source of timber. Parts of Belair have views of the city of Adelaide, the Adelaide Plains and the coast...
South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
, substantially different in appearance.
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 TunnelHoosac Tunnel
The Hoosac Tunnel is a 4.75-mile-long railroad tunnel in western Massachusetts which passes through the Hoosac Range, an extension of Vermont's Green Mountains. Work began in 1848 and was finally completed in 1875...
which was duplicated by enlarging the bore.
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 HamiltonHamilton railway station, New South Wales
-Hamilton Junction Signal Box:Hamilton Junction Signal Box is separated from Hamilton Station by Beaumont Street Level Crossing. The elegant Victorian signal box was built by McKenzie & Holland in 1897, making it one of the oldest surviving mechanical signal boxes in Australia, and also one of the...
line in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
which was constructed as mainly single track in the 1880s, with full duplication only completed around 1910. All bridges, tunnels, stations, and earthworks were built for double track. The former Baltimore and Ohio Railroad
Baltimore and Ohio Railroad
The Baltimore and Ohio Railroad was one of the oldest railroads in the United States and the first common carrier railroad. It came into being mostly because the city of Baltimore wanted to compete with the newly constructed Erie Canal and another canal being proposed by Pennsylvania, which...
(B&O) line between Baltimore
Baltimore
Baltimore is the largest independent city in the United States and the largest city and cultural center of the US state of Maryland. The city is located in central Maryland along the tidal portion of the Patapsco River, an arm of the Chesapeake Bay. Baltimore is sometimes referred to as Baltimore...
and Jersey City, now owned by CSX and Conrail Shared Assets Operations, 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 and Philadelphia, Pennsylvania
Philadelphia, Pennsylvania
Philadelphia is the largest city in the Commonwealth of Pennsylvania and the county seat of Philadelphia County, with which it is coterminous. The city is located in the Northeastern United States along the Delaware and Schuylkill rivers. It is the fifth-most-populous city in the United States,...
when CSX increased freight schedules in the late 1990s.
Also Smardale Gill viaduct.
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:- Swanage RailwaySwanage RailwayThe Swanage Railway is a long heritage railway in the Purbeck district of Dorset, England. The railway follows the route of the Purbeck branch line between Norden railway station, Corfe Castle railway station, Harman's Cross railway station, Herston Halt railway station and Swanage...
- Bluebell RailwayBluebell RailwayThe Bluebell Railway is a heritage line running for nine miles along the border between East and West Sussex, England. Steam trains are operated between and , with an intermediate station at .The railway is managed and run largely by volunteers...
: Horsted KeynesHorsted KeynesHorsted Keynes is a village and civil parish in the Mid Sussex District of West Sussex, England. The village is located about eight kilometres north east of Haywards Heath, in the Weald...
to LewesLewesLewes is the county town of East Sussex, England and historically of all of Sussex. It is a civil parish and is the centre of the Lewes local government district. The settlement has a history as a bridging point and as a market town, and today as a communications hub and tourist-oriented town...
. - Keighley and Worth Valley RailwayKeighley and Worth Valley RailwayThe Keighley and Worth Valley Railway is a long branch line that served mills and villages in the Worth Valley and is now a heritage railway line in West Yorkshire, England. It runs from Keighley to Oxenhope. It connects to the national rail network line at Keighley railway station...
- including bridge and tunnels and a deviation. - Westerham in KentKentKent is a county in southeast England, and is one of the home counties. It borders East Sussex, Surrey and Greater London and has a defined boundary with Essex in the middle of the Thames Estuary. The ceremonial county boundaries of Kent include the shire county of Kent and the unitary borough of...
. - Mid-Wales RailwayMid-Wales Railway-Company Formation and Parliamentary authorisation:The company was formed in 1859 and parliamentary approval was received on 1 August for the northern section of the line from Llanidloes, Montgomeryshire to Llandovery, Carmarthenshire...
(parts). - Monkerei Tunnel in New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
- double track size at summit reduces fume problem in tunnel. - Golgotha Tunnel near EythorneEythorneEythorne is a civil parish and small village of about 1000 homes, located 7.3 miles NNW of Dover in Kent. There are currently about 2500 residents. Eythorne holds many historical attributes. Situated a few miles away from Dover beach, it offers many articles of evidence of the war...
on East Kent Light RailwayEast Kent Light RailwayThe East Kent Light Railway was part of the Colonel Stephens group of cheaply built rural light railways in England. Holman Fred Stephens was engineer from its inception, subsequently becoming director and manager...
was only partly excavated for the second track.
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 TunnelConnaught Tunnel
Connaught Tunnel, in the Selkirk Mountains under Rogers Pass on the Canadian Pacific Railway main line between Calgary, Alberta, and Revelstoke, British Columbia, at long was, at the time it was built, the longest railway tunnel in North America. Dug under Mount Macdonald to ease growing traffic...
in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
or the Tickhole Tunnel in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. 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
Hastings 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 London via Sevenoaks.-Openings:The line was opened by the South Eastern Railway in main three stages: – :...
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).
As part of the Regional Fast Rail
Regional Fast Rail project
The Regional Fast Rail project was a rail transport project of the State Government of Victoria, Australia undertaken between 2000 and 2006 aimed at improving the passenger services on the Victorian regional railway network , specifically to reduce travel times, enhance service frequency and...
(RFR) railway upgrade 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.
A similar process can be followed on narrow bridges (like the bridge north of Drogheda railway station
Drogheda railway station
Drogheda MacBride railway station serves Drogheda in County Louth, Ireland. There is a railcar servicing depot for commuter trains here.The original Drogheda station opened on 25 May 1844 about a quarter mile southeast. The passenger station was resited when the first temporary Boyne Viaduct...
in Ireland
Republic of Ireland
Ireland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...
).
The bridge over the Murray River
Murray River
The Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...
between Albury
Albury, New South Wales
Albury is a major regional city in New South Wales, Australia, located on the Hume Highway on the northern side of the Murray River. It is located wholly within the boundaries of the City of Albury Local Government Area...
and Wodonga is double track, but because of weakness in the bridge only one train is allowed on it at a time.
Other tunnel singling
- Hoosac TunnelHoosac TunnelThe Hoosac Tunnel is a 4.75-mile-long railroad tunnel in western Massachusetts which passes through the Hoosac Range, an extension of Vermont's Green Mountains. Work began in 1848 and was finally completed in 1875...
, Guilford Rail System, Massachusetts, US. - Old Main Line Subdivision, B&O, Maryland, US. Entire 58 miles (93.3 km) subdivision was single tracked to utilize higher clearances of the 9 tunnels on the line.
- Whitehall TunnelWhitehall TunnelThe Whitehall Tunnel in Allegheny County, Pennsylvania was originally built by the B&O Railroad in 1899 as a double-track tunnel. The tunnel was completed in 1900....
, B&O, Pennsylvania, US.
Triple track
Severe gradients made the headway in the uphill direction much worse than the headway in the downhill direction. Between Whittingham and MaitlandMaitland
Maitland is an English and Scottish surname. It arrived in Britain after the Norman conquest of 1066. There are two theories about its source. It is either a nickname reference to "bad temper/disposition" , or it may be a locational reference to Mautalant, a place in Pontorson, France...
, a third track is being provided 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
Stockholm Central Station
Stockholm Central Station is the largest railway station in Sweden. The station is situated in the district of Norrmalm at Vasagatan/Central Plan. Opened July 18, 1871, the station is the largest in Sweden, with over 200,000 visitors daily...
, but were cancelled in favor to Citybanan
Citybanan
The Stockholm City Line is a railway tunnel under construction beneath central Stockholm in Sweden which will be used by the Stockholm Commuter Rail. The line will be long, double track and electrified. It will have two stations: Stockholm City Station will be located directly below T-Centralen,...
.
Quadruple track
Quadruple trackQuadruple track
Quadruple track railway consists of four parallel tracks. On a quad-track line, two tracks are used in each direction. It is also sometimes called four-track railway....
consists of four parallel tracks. On a quad-track line, faster trains can overtake slower ones. Quadruple track is mostly used when there are both local trains that stop often, and also faster inter-city or high speed trains.
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. At FramptonFrampton, New South Wales
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 and 11 kilometres north east from Bethungra....
, New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
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.
A similar arrangement to Frampton cannot have been adopted between Rydal
Rydal, New South Wales
Rydal is a small village in New South Wales, Australia.Rydal is located about west of the state capital, Sydney and south-west from the town of Lithgow....
and Sodwalls 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
Gunning, New South Wales
Gunning is a town on the Old Hume Highway, between Goulburn and Yass in the Southern Tablelands of New South Wales, Australia, about 260 km south-west of Sydney and 75 km north of the national capital, Canberra. On Census night 2006, Gunning had a population of 487 people...
.
Between Junee
Junee, New South Wales
Junee is a medium sized town in the Riverina region of New South Wales, Australia. The town's prosperity and mixed services economy is based on a combination of agriculture, rail transport, light industry and government services, and in particular correctional services...
and Marina, New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
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
Cut and fill
In earthmoving, cut and fill is the process of constructing a railway, road or canal whereby the amount of material from cuts roughly matches the amount of fill needed to make nearby embankments, so minimizing the amount of construction labor...
.
At Bethungra, New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, the downhill track follows the original short and steep alignment, while the uphill track follows a longer, more easily graded alignment including a spiral
Spiral (railway)
A spiral is a technique employed by railways to ascend steep hills.A railway spiral rises on a steady curve until it has completed a loop, passing over itself as it gains height, allowing the railway to gain vertical elevation in a relatively short horizontal distance...
.
At Saunderton
Saunderton
Saunderton is a village in Buckinghamshire, England. It is located in a valley of the Chiltern Hills, about three and a half miles north west of High Wycombe, four miles south of Princes Risborough. It lies on the main A4010 road, and has a station on the Chiltern Main Line between the two...
, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, 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 ok centres
The distance betrains follow a more gently graded new construction through a tunnel. This scheme avoided the cost of a new double track tunnel.
Directional running Directional running is when two tracks that were built as separate lines are operationally combined to act as a double track line. An example of directional running occurs in central Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
. The Western Pacific
Western Pacific Railroad
The Western Pacific Railroad was a Class I railroad in the United States. It was formed in 1903 as an attempt to break the near-monopoly the Southern Pacific Railroad had on rail service into northern California...
and Southern Pacific Railroad
Southern Pacific Railroad
The Southern Pacific Transportation Company , earlier Southern Pacific Railroad and Southern Pacific Company, and usually simply called the Southern Pacific or Espee, was an American railroad....
s, longtime rivals who each built and operated tracks between northern California
Northern California
Northern California is the northern portion of the U.S. state of California. The San Francisco Bay Area , and Sacramento as well as its metropolitan area are the main population centers...
and Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, agreed to share their lines between meeting points near Winnemucca
Winnemucca, Nevada
-Demographics:As of the census of 2000, there were 7,174 people, 2,736 households, and 1,824 families residing in the city. The population density was 867.5 people per square mile . There were 3,280 housing units at an average density of 396.6 per square mile...
and Wells
Wells, Nevada
Wells is a city in Elko County, in northeast Nevada in the western United States. The population was 1,346 at the 2000 census. Wells is located at the junction of U.S. Route 93 and Interstate 80, approximately east of Elko and is part of the Elko Micropolitan Statistical Area.-History:The site...
, a distance of approximately 180 miles (289.7 km). Westbound trains from both companies used the Southern Pacific's Overland Route
Overland Route (Union Pacific Railroad)
The Overland Route was a train route operated jointly by the Union Pacific Railroad and the Central Pacific Railroad / Southern Pacific Railroad, between Council Bluffs, Iowa / Omaha, Nebraska, and San Francisco, California over the grade of the First Transcontinental Railroad which had been...
while eastbound trains used the Western Pacific's Feather River Route
Feather River Route
The Feather River Route is a rail line that was built and operated by the Western Pacific Railroad. It was constructed between 1906 and 1909, and connects the cities of Oakland, California, and Salt Lake City, Utah...
(now called the Central Corridor
Central Corridor (Union Pacific Railroad)
The Central Corridor is a rail line operated by the Union Pacific Railroad from near Winnemucca, Nevada to Denver, Colorado in the western United States. The line is in use for freight, and provides the route of the California Zephyr. The BNSF Railway has trackage rights on the entire line. The...
).
Where the lines ran in close proximity, crossovers were constructed to allow reverse movements. This was necessary as at points the two tracks are several miles apart and some destinations can be only be accessed from one of the lines. The Union Pacific Railroad
Union Pacific Railroad
The Union Pacific Railroad , headquartered in Omaha, Nebraska, is the largest railroad network in the United States. James R. Young is president, CEO and Chairman....
has since acquired both of these lines; however, continues to operate them as separate lines in a directional running setup.
Canadian Pacific and Canadian National
Canadian National Railway
The Canadian National Railway Company is a Canadian Class I railway headquartered in Montreal, Quebec. CN's slogan is "North America's Railroad"....
are starting to do the same. Another example was in Conshohocken, Pennsylvania
Conshohocken, Pennsylvania
Conshohocken is a borough on the Schuylkill River in Montgomery County, Pennsylvania, in suburban Philadelphia. Historically a large mill town and industrial and manufacturing center, after the decline of industry in recent years Conshohocken has developed into a center of riverfront commercial and...
where the former Reading Railroad and Pennsylvania Railroad
Pennsylvania Railroad
The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....
shared lines, and even overhead electrical wire supports, for a 2-mile stretch on the northern bank of the Schuylkill River
Schuylkill River
The Schuylkill River is a river in Pennsylvania. It is a designated Pennsylvania Scenic River.The river is about long. Its watershed of about lies entirely within the state of Pennsylvania. The source of its eastern branch is in the Appalachian Mountains at Tuscarora Springs, near Tamaqua in...
. Both lines eventually came under Conrail ownership in 1976 with the former PRR line being abandoned and now used as a hike/bike path.
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 controlCentralized traffic control
Centralized traffic control is a form of railway signalling that originated in North America and centralizes train routing decisions that were previously carried out by local signal operators or the train crews themselves. The system consists of a centralized train dispatcher's office that...
.