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Encyclopedia > Double track
A BNSF Railway intermodal train passes some maintenance of way equipment on the double track mainline in Prairie du Chien, Wisconsin.
A BNSF Railway intermodal train passes some maintenance of way equipment on the double track mainline in Prairie du Chien, Wisconsin.

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. An audio recording technique, in which a performer sings or plays along with their own prerecorded part, for dramatic effect or to produce a stronger sound than with a single voice or instrument. ... An eastbound BNSF train at Prairie du Chien, Wisconsin. ... An eastbound BNSF train at Prairie du Chien, Wisconsin. ... The BNSF Railway (AAR reporting marks BNSF), headquartered in Fort Worth, Texas, is one of the four remaining transcontinental railroads and one of the largest railroad networks in North America (only one competitor, the Union Pacific Railroad, is larger in size). ... An intermodal train carrying both shipping containers and highway semi-trailers in piggyback service, on flatcars, passes through the Cajon Pass in February, 1995. ... Maintenance of way (often abbreviated as M of Way, MOW or MW) refers to the maintenance of railroad rights of way. ... Sign seen in Prairie du Chien, WI on entering from Iowa. ... A single track railway A single track railway is one where traffic in both directions shares the same track. ...

Contents

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. Also the lines tended to be busy enough to be beyond the capacity of single track anyway. Telegraphy (from the Greek words tele = far away and grapho = write) is the long distance transmission of written messages without physical transport of letters, originally over wire. ...


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. This improved with the development of the telegraph and the train order system. Telegraphy (from the Greek words tele = far away and grapho = write) is the long distance transmission of written messages without physical transport of letters, originally over wire. ... Train order operation is a system by which the railroads of North America conveyed operating instructions before the days of centralized traffic control and use of track warrants conveyed by radio. ...


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. Thus in Belgium, France (apart from the former German Alsace and Lorraine), Switzerland, Italy and Taiwan for example, the railways use left hand running, while the roads use right hand running.  drive on right drive on left Driving on either the left or the right side of the road reduces the incidence of vehicles being involved in head-on collisions with each other. ...


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. Overpass in East Potomac Park, Washington, D.C. Flyover in Miami Beach, Florida An overpass (In UK, most Commonwealth countries flyover) is a bridge, road or similar structure that crosses over another road. ...


Many countries do not have a great amount of double 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 because of damage or some obstruction. ...


Crossing loops

Crossing loops, while consisting of two or more tracks, are not normally regarded as double track. 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. A crossing loop is a place on a single line railway where trains in opposing directions can cross each other. ...


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. See single-line working for a discussion of this topic. The British terminal at Cheriton in west Folkestone, from the Pilgrims Way. ... A single track railway is one where traffic in both directions shares the same track. ... 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. ...


Accidents can occur if the temporary safeworking system is not implemented properly.

Detail of an aerial photograph showing the crash scene The Zoufftgen rail crash occurred on October 11, 2006, near Zoufftgen, Moselle, France, close to Metz and the border with Luxembourg. ...

Construction

Duplication

The process of expanding a single track to double track is called duplication or doubling. A single track railway 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. Twinned structure may be identical in appearance, or like some tunnels between Adelaide and Belair South Australia, substantially different in appearance. // The Ilfracombe Branch of the London & South Western Railway (LSWR) ran between Barnstaple and Ilfracombe in North Devon. ... For other uses, see Adelaide (disambiguation). ... Belair is an alternate name used for Satan, in particular, in the Questions of Bartholomew. ... Capital Adelaide Government Constitutional monarchy Governor Marjorie Jackson-Nelson Premier Mike Rann (ALP) Federal representation  - House seats 11  - Senate seats 12 Gross State Product (2004-05)  - Product ($m)  $59,819 (5th)  - Product per capita  $38,838/person (7th) Population (End of September 2006)  - Population  1,558,200 (5th)  - Density  1. ...


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 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. 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. Strathfield is a suburb of Sydney, Australia, a significant centre in Sydneys Inner West. ... Hamilton is a railway station located in Newcastle, New South Wales,Australia on the Newcastle & Central Coast Line, and the Hunter Line. ... “NSW” redirects here. ... The Baltimore and Ohio Railroad or B&O was a 19th century railroad which operated in the east coast of the United States and was the first railroad to offer commercial transportation of both people and freight. ... Categories: Companies traded on NYSE | Railway companies of the United States | Alabama railroads | Connecticut railroads | Delaware railroads | Florida current railroads | Georgia railroads | Illinois railroads | Indiana railroads | Kentucky railroads | Louisiana railroads | Maryland railroads | Massachusetts railroads | Michigan railroads | Mississippi railroads | New Jersey railroads | New York railroads | North Carolina railroads | Ohio railroads | Pennsylvania... Baltimore redirects here. ... Nickname: City of Brotherly Love, Philly, the Quaker City Motto: Philadelphia maneto (Let brotherly love continue) Location in Pennsylvania Coordinates: Country United States State Pennsylvania County Philadelphia Founded October 27, 1682 Incorporated October 25, 1701 Mayor John F. Street (D) Area    - City 369. ...


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:

1638 U class at Sheffield Park station The Bluebell Railway is a heritage line running for nine miles along the border between East Sussex and West Sussex, England. ... The view looking along the Horsted Keynes village green Horsted Keynes is a village and civil parish in the Mid Sussex District of West Sussex, England. ... This is about Lewes in England. ... Ivatt 2MT 2-6-2T 41241 at Haworth station The Platform, Oxenhope Railway Station, terminus of the Keighley and Worth Valley Railway (photo by Nigel Homer, 2006) Damems Junction signal box The Keighley and Worth Valley Railway is a five-mile (eight-km) long heritage railway line in West Yorkshire... The Westerham branch in relation to other railway lines in Kent The Westerham Valley Branch Line was a short railway line in Kent that connected Westerham, Brasted and Chevening with the village of Dunton Green and the South Eastern Main Line, a distance of 4. ... For other uses, see Kent (disambiguation). ... “NSW” redirects here. ...

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. 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). Connaught Tunnel, in the Selkirk Mountains under Rogers Pass on the Canadian Pacific Railway main line between Calgary, Alberta, and Revelstoke, British Columbia, at 5. ... “NSW” redirects here. ... The Hastings Line is a railway line in Kent and Sussex, which links Hastings with Tonbridge, and from there into London via Sevenoaks. ...


Other tunnel singling

The Hoosac Tunnel is a 4. ...

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. 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. 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. Frampton is a community area 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. ... “NSW” redirects here. ... Looking up Humphries Street, Junee Junee is a small town and local government area (see Junee Shire) in the Riverina region of New South Wales, Australia. ... “NSW” redirects here. ... Cut and Fill is the process of building a railway or road whereby the amount of earth cut from cuttings roughly matches the amount of fill needed to make nearby embankments. ...


Split ownership

An unusual stretch of double track in the west of the United States is actually comprised of two separate single track lines owned by separate companies. 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. Another example is 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. Both lines eventually came under Conrail ownership in 1976 with the former PRR line being abandoned and is now a hike/bike path. A single track railway A single track railway is one where traffic in both directions shares the same track. ... The Canadian Pacific Railway (CPR; AAR reporting marks CP, CPAA, CPI), known as CP Rail between 1968 and 1996, is a Canadian Class I railway that is operated by Canadian Pacific Railway Limited. ... The Canadian National Railway (CN; AAR reporting marks CN, CNA, CNIS) is a Canadian Class I railway operated by the Canadian National Railway Company headquartered in Montreal, Quebec. ... Conshohocken is a borough on the Schuylkill River in Montgomery County, Pennsylvania, in suburban Philadelphia. ... Philadelphia and Reading Railroad Categories: Rail stubs | Philadelphia and Reading Railroad ... 1893 map The Pennsylvania Railroad (AAR reporting mark PRR) was an American railroad that was founded in 1846 and merged in 1968 into Penn Central Transportation. ... Conrail 6114, a GE Dash 8-40CW, leads a train westbound out of Altoona, Pennsylvania. ...


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. ...


References

  1. ^ Railway Masterpieces by Brian Solomon 0-87349-323-0 p122

  Results from FactBites:
 
Double track - Wikipedia, the free encyclopedia (1010 words)
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 double track lines in any country generally keep to one side of the road, which is not necessarily the same side that road vehicles in that country keep to.
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.
  More results at FactBites »

 
 

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