The railway track or permanent way is the elements of

railway Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...

lines: generally the pairs of

rails Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

typically laid on the

sleepers ''Sleepers'' is a 1996 American legal crime drama film written, produced, and directed by Barry Levinson, and based on Lorenzo Carcaterra's 1995 book of the same name. The film stars Kevin Bacon, Jason Patric, Brad Pitt, Robert De Niro, Dustin H ...

or ties embedded in ballast, intended to carry the ordinary trains of a railway. It is described as permanent way because in the earlier days of railway construction, contractors often laid a temporary track to transport spoil and materials about the site; when this work was substantially completed, the temporary track was taken up and the permanent way installed. The earliest tracks consisted of wooden rails on transverse wooden sleepers, which helped maintain the spacing of the rails. Various developments followed, with

cast iron Cast iron is a class of iron– carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impur ...

plates laid on top of the wooden rails and later

wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag inclusions (up to 2% by weight), which give it a wood-like "grain" ...

plates or wrought iron angle plates ( angle iron as L-shaped plate rails). Rails were also individually fixed to rows of stone blocks, without any cross ties to maintain correct separation. This system also led to problems, as the blocks could individually move. The first version of

Isambard Kingdom Brunel Isambard Kingdom Brunel (; 9 April 1806 – 15 September 1859) was a British civil engineer who is considered "one of the most ingenious and prolific figures in engineering history," "one of the 19th-century engineering giants," and "on ...

's broad gauge system used rails laid on longitudinal sleepers whose rail gauge and elevation were pinned down by being tied to piles (conceptually akin to a pile bridge), but this arrangement was expensive and Brunel soon replaced it with what became the classic broad gauge track, in which the piles were forgone and transoms, similar to sleepers, maintained the rail gauge. Today, most rail track uses the standard system of rail and sleepers;

ladder track Ladder track is a type of railway track in which the track is laid on longitudinal supports with transverse connectors holding the two rails at the correct gauge distance. Modern ladder track can be considered a development of baulk road, which ...

is used in a few applications. Developments in manufacturing technologies has led to changes to the design, manufacture and installation of rails, sleepers and the means of attachments. Cast iron rails, long, began to be used in the 1790s and by 1820, long wrought iron rails were in use. The first steel rails were made in 1857 and standard rail lengths increased over time from . Rails were typically specified by units of weight per linear length and these also increased. Railway sleepers were traditionally made of

Creosote Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics. Some creosote types were ...

-treated hardwoods and this continued through to modern times. Continuous welded rail was introduced into Britain in the mid 1960s and this was followed by the introduction of concrete sleepers.

Wooden tracked systems

Plank ways

The earliest use of a railway track seems to have been in connection with mining in Germany in the 12th century. Mine passageways were usually wet and muddy, and moving barrows of ore along them was extremely difficult. Improvements were made by laying timber planks so that wheeled containers could be dragged along by manpower. By the 16th century, the difficulty of keeping the wagon running straight had been solved by having a pin going into a gap between the planks.

Georg Agricola Georgius Agricola (; born Georg Pawer or Georg Bauer; 24 March 1494 – 21 November 1555) was a German Humanist scholar, mineralogist and metallurgist. Born in the small town of Glauchau, in the Electorate of Saxony of the Holy Roman Emp ...

describes box-shaped carts, called "dogs", about half as large again as a wheelbarrow, fitted with a blunt vertical pin and wooden rollers running on iron axles. An

Elizabethan era The Elizabethan era is the epoch in the Tudor period of the history of England during the reign of Queen Elizabeth I (1558–1603). Historians often depict it as the golden age in English history. The symbol of Britannia (a female personific ...

example of this has been discovered at Silvergill in

Cumbria Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. C ...

, England, and they were probably also in use in the nearby Mines Royal of Grasmere, Newlands and Caldbeck. Where space permitted round-section wooden tracks to take trucks with flanged wheels were installed: a painting from 1544 by the Flemish artist

Lucas Gassel Lucas Gassel or Lucas van Gassel ( Deurne, Netherlands, c. 1485 – Brussels, 1568 or 1569)Lucas Gassel
at the

shows a coppermine with rails of this type emerging from an

adit An adit (from Latin ''aditus'', entrance) is an entrance to an underground mine which is horizontal or nearly horizontal, by which the mine can be entered, drained of water, ventilated, and minerals extracted at the lowest convenient level. Adit ...

Edged rails

A different system was developed in England, probably in the late 16th century, near

Broseley Broseley is a market town in Shropshire, England, with a population of 4,929 at the 2011 Census and an estimate of 5,022 in 2019. The River Severn flows to its north and east. The first The Iron Bridge, iron bridge in the world was built in 17 ...

for conveying coal from mines, sometimes

drift mine Drift mining is either the mining of an ore deposit by underground methods, or the working of coal seams accessed by adits driven into the surface outcrop of the coal bed. A drift mine is an underground mine in which the entry or access is above ...

s down the side of the Severn Gorge to the

River Severn , name_etymology = , image = SevernFromCastleCB.JPG , image_size = 288 , image_caption = The river seen from Shrewsbury Castle , map = RiverSevernMap.jpg , map_size = 288 , map_c ...

. This, probably a rope-hauled incline plane, had existed 'long before' 1605. This probably preceded the

Wollaton Wagonway The Wollaton Wagonway (or Waggonway), built between October 1603 and 1604 in the East Midlands of England by Huntingdon Beaumont in partnership with Sir Percival Willoughby, has sometimes been credited as the world's first ''overground'' wagon ...

of 1604, which has hitherto been regarded as the first. In Shropshire, the gauge was usually narrow, to enable the wagons to be taken underground in drift mines. However, by far the greatest number of wagonways were near

Newcastle upon Tyne Newcastle upon Tyne ( RP: , ), or simply Newcastle, is a city and metropolitan borough in Tyne and Wear, England. The city is located on the River Tyne's northern bank and forms the largest part of the Tyneside built-up area. Newcastle is ...

, where a single wagon was hauled by a horse on a wagonway of about the modern standard gauge. These took coal from the pithead down to a staithe, where the coal was loaded into river boats called keels. Wear of the timber rails was a problem. They could be renewed by turning them over, but had to be regularly replaced. Sometimes, the rail was made in two parts, so that the top portion could easily be replaced when worn out. The rails were held together by wooden sleepers, covered with ballast to provide a surface for the horse to walk on.

Early iron rails

Cast iron strips could be laid on top of timber rails, and the use of such materials probably occurred in 1738, but there are claims that this technology went back to 1716. In 1767,

Ketley ironworks Ketley Ironworks was an ironworks in Ketley, in Shropshire, England. Established in 1756, it was one of the largest ironworks in Britain during its ownership by William Reynolds and his brother Joseph. The site's location is

began producing

plates, which were fixed to the top of wooden rails with nails, to provide a more durable running surface. This construct was known as strap-iron rail (or strap rail) and was widely used on pre-steam railways in the United States. – This section describes strap rails, their uses and problems in considerable detail.'' Although relatively cheap and quick to build, they were unsuited to heavy loads and required 'excessive maintenance'. Train wheels rolling over the spikes loosened them, allowing the rail to break free and curve upwards sufficiently that a car wheel could get beneath it and force the end of the rail up through the floor of the car, writhing and twisting, endangering passengers. These broken rails became known as "snake heads". When wrought iron became available, wrought iron plates provided an even more durable surface. The rails had projecting lugs (or ears) with a hole to enable them to be fixed to the underlying wooden rail.

Iron plateways

An alternative was developed by

John Curr John Curr (c. 1756 – 27 January 1823) was the manager or viewer of the Duke of Norfolk's collieries in Sheffield, England from 1781 to 1801. During this time he made a number of innovations that contributed significantly to the development of t ...

of Sheffield, the manager of the

Duke of Norfolk Duke of Norfolk is a title in the peerage of England. The seat of the Duke of Norfolk is Arundel Castle in Sussex, although the title refers to the county of Norfolk. The current duke is Edward Fitzalan-Howard, 18th Duke of Norfolk. The dukes ...

's colliery there. This had a L-shaped rail, so that the flange was on the rail rather than on the wheel. This was also used by

Benjamin Outram Benjamin Outram (1 April 1764 – 22 May 1805) was an English civil engineer, surveyor and industrialist. He was a pioneer in the building of canals and tramways. Life Born at Alfreton in Derbyshire, he began his career assisting his father J ...

of Butterley Ironworks and

William Jessop William Jessop (23 January 1745 – 18 November 1814) was an English civil engineer, best known for his work on canals, harbours and early railways in the late 18th and early 19th centuries. Early life Jessop was born in Devonport, Devon, the ...

(who became a partner in them in 1790). These were used to transport goods for relatively short distances down to canals, though Curr's ran between the manor colliery and

Sheffield Sheffield is a city in South Yorkshire, England, whose name derives from the River Sheaf which runs through it. The city serves as the administrative centre of the City of Sheffield. It is historically part of the West Riding of Yorkshire a ...

town. These rails are referred to as plates, and the railway is sometimes called a plateway. The term "platelayer" also derives from this origin. In theory, the unflanged wheels could have been used on ordinary highways, but in practice this was probably rarely done, because the wagon wheels were so narrow that they would have dug into the road surface. The system found wide adoption in Britain. Often, the plates were mounted on stone blocks, and sometimes without sleepers, but that was liable to cause the rails to spread apart, increasing the gauge. Railways of this kind were widely used in south Wales, particularly to transport limestone down to the ironworks, and then to take the iron to a canal, sometimes several miles away, which took the products to market. The rails were at first made of cast iron, typically in lengths of , spanning between stone blocks.J. van Laun, ''Early limestone railways'' (Newcomen Society, London, 2001. The stone blocks had been assumed to be permanent, but experience quickly showed that they settled and gradually moved under traffic, creating chaotic

track geometry Track geometry is concerned with the properties and relations of points, lines, curves, and surfaces in the three-dimensional positioning of railroad track. The term is also applied to measurements used in design, construction and maintenance of t ...

and causing derailments. Another problem was that the running surface was liable to become obstructed by stones, displaced from the ballast. An alternative was to use an iron tie bar to keep the rails to the proper gauge, incorporating a shoe in which the rail was fixed. An example of this was the Penydarren or Merthyr tramway. This was used by

Richard Trevithick Richard Trevithick (13 April 1771 – 22 April 1833) was a British inventor and mining engineer. The son of a mining captain, and born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age. He w ...

to demonstrate a pioneer locomotive in 1804, using one of his high pressure steam engines, but the engine was so heavy that it broke many of the rails.

Early edge rails

Cast iron edge rails were used by

Thomas Dadford junior Thomas Dadford Jr. (ca. 1761 to 1801) was an English canal engineer, who came from a family of canal engineers. He first worked with his father in the north of Britain on the Stour and the Trent, but later independently, contributing to a number ...

when building the Beaufort and

Blaenavon Blaenavon ( cy, Blaenafon) is a town and community in Torfaen county borough, Wales, high on a hillside on the source of the Afon Lwyd. It is within the boundaries of the historic county of Monmouthshire and the preserved county of Gwent. Th ...

lines to the

Monmouthshire canal Monmouthshire ( cy, Sir Fynwy) is a county in the south-east of Wales. The name derives from the historic county of the same name; the modern county covers the eastern three-fifths of the historic county. The largest town is Abergavenny, wit ...

in 1793. These were rectangular, in width with a depth of and in length, and required flanges on the wagon wheels. The same year,

used edge rails on the Cromford Canal. T-shaped beams were used by William Jessop on the

Loughborough Loughborough ( ) is a market town in the Charnwood borough of Leicestershire, England, the seat of Charnwood Borough Council and Loughborough University. At the 2011 census the town's built-up area had a population of 59,932 , the second large ...

Nanpantan Nanpantan is a suburb in the Charnwood borough of Leicestershire, England. It is located in the south-west of the town of Loughborough, but the village is slightly separated from the main built-up area of Loughborough. It is also the site of ...

line in 1794, and his sons used I-shaped beams in 1813–15 on a railway from

Grantham Grantham () is a market and industrial town in the South Kesteven district of Lincolnshire, England, situated on the banks of the River Witham and bounded to the west by the A1 road. It lies some 23 miles (37 km) south of the Lincoln and ...

Belvoir Castle Belvoir Castle ( ) is a faux historic castle and stately home in Leicestershire, England, situated west of the town of Grantham and northeast of Melton Mowbray. The Castle was first built immediately after the Norman Conquest of 1066 an ...

. Samples of these rails are held in the Science Museum, London. A short-lived alternative was the ''fish-bellied'' profile, first used by Thomas Barnes (1765–1801) at Walker Colliery, near

Newcastle Newcastle usually refers to: *Newcastle upon Tyne, a city and metropolitan borough in Tyne and Wear, England *Newcastle-under-Lyme, a town in Staffordshire, England *Newcastle, New South Wales, a metropolitan area in Australia, named after Newcastle ...

in 1798, which enabled rails to have a longer span between blocks. These were T-section edge rails, three feet long and laid on transverse stone sleepers. These were still made of

Butt and lap joints

The earliest rails had square butt joints, which were weak and difficult to keep in alignment.

George Stephenson George Stephenson (9 June 1781 – 12 August 1848) was a British civil engineer and mechanical engineer. Renowned as the "Father of Railways", Stephenson was considered by the Victorians In the history of the United Kingdom and the ...

introduced lapped joints, which maintained their alignment quite well.

Modern edge rails

The breakthrough came when

John Birkinshaw John Birkinshaw (1777-1842) was a 19th-century railway engineer from Bedlington, Northumberland noted for his invention of wrought iron rails in 1820 (patented on October 23, 1820). Up to this point, rail systems had used either wooden rails, w ...

Bedlington Ironworks Bedlington Ironworks, in Blyth Dene, Northumberland, England, operated between 1736 and 1867. It is most remembered as the place where wrought iron rails were invented by John Birkinshaw in 1820, which triggered the railway age, with their fir ...

Northumberland Northumberland () is a county in Northern England, one of two counties in England which border with Scotland. Notable landmarks in the county include Alnwick Castle, Bamburgh Castle, Hadrian's Wall and Hexham Abbey. It is bordered by land ...

developed rolled

rails in 1820 in lengths, as used for the Stockton and Darlington Railway. This was strong enough to bear the weight of a locomotive and of a train of wagons (or carriages) pulled by it. This marks the beginning of the modern rail era. This system was instantly successful, although some false starts took place. Some early rails were made in a T cross section, but the lack of metal at the foot limited the bending strength of the rail, which has to act as a beam between supports. As metal technologies improved, these wrought iron rails were made progressively somewhat longer, and with a heavier, and therefore stronger, cross-section. By providing more metal in the foot of the rail, a stronger beam was created, achieving much better strength and stiffness, and a section was created similar to the bullhead rail section still visible today. This was expensive, however, and the promoters of early railways struggled with decisions about the appropriate weight (and therefore strength, and cost) of their rails. At first, the rail section was almost symmetrical top-to-bottom, and was described as a double-headed rail. The intention was to invert the rail after the top surface had become worn, but rails tend to develop chair gall, an attrition of the rail where it is supported in the chairs, and this would have made running on the former bottom surface impossibly noisy and irregular. It was better to provide the extra metal on the top surface and gain extra wear there without the need to invert the rail at its half life. Many railways preferred a flat bottom rail section, where the rails could be laid directly on the sleepers, representing a marked cost saving. Indenting of the sleeper was the problem; where the traffic was heavy, it became necessary to provide a sole plate under the rails to spread the load on the tie, partly vitiating the cost saving. However, in main line situations, this form found almost universal adoption in North America and Australia, and in much of continental Europe. The United Kingdom persisted with bullhead rail in main line use, with widespread introduction of flat-bottom rail only starting in about 1947.

Steel rails

The first rails made from steel were made in 1857, when

Robert Forester Mushet Robert Forester Mushet (8 April 1811 – 29 January 1891) was a British metallurgist and businessman, born on 8 April 1811, in Coleford, in the Forest of Dean, Gloucestershire, England. He was the youngest son of Scottish parents, Agnes Wilson ...

remelted scrap steel from an abortive Bessemer trial, in crucibles at Ebbw Vale ironworks, and were laid experimentally at

Derby railway station Derby railway station (, also known as Derby Midland) is a main line railway station serving the city of Derby in Derbyshire, England. Owned by Network Rail and managed by East Midlands Railway, the station is also used by CrossCountry services ...

on the

Midland Railway The Midland Railway (MR) was a railway company in the United Kingdom from 1844. The Midland was one of the largest railway companies in Britain in the early 20th century, and the largest employer in Derby, where it had its headquarters. It ama ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. The rails proved far more durable than the iron rails they replaced and remained in use until 1873.

Henry Bessemer Sir Henry Bessemer (19 January 1813 – 15 March 1898) was an English inventor, whose steel-making process would become the most important technique for making steel in the nineteenth century for almost one hundred years from 1856 to 1950. H ...

supplied 500 tons of steel blooms to the London and North Western Railway's rail mill at Crewe in 1860. Several other companies began producing steel rails in the following years.Barraclough 1990, 67. The transition to steel rails was hastened by the introduction of open hearth steelmaking.

William Siemens Sir Carl Wilhelm Siemens (4 April 1823 – 19 November 1883), anglicised to Charles William Siemens, was a German-British electrical engineer and businessman. Biography Siemens was born in the village of Lenthe, today part of Gehrden, near Ha ...

set up his Landore steelworks partly to supply rail to the Great Western Railway. A boom in rail production followed, but a banking crisis in America slowed the rate at which railways were built there and orders to British rail producers. The British iron and steel industry went into a recession, which particularly affected the wrought iron sector. When demand for rails began to grow again, it was largely for steel rails, which were more durable than those of iron.

Associated features

Sleepers

Timber sleepers, that is transverse beams supporting the two rails that form the track, replaced the individual stone blocks formerly used. This system has the major advantage that maintenance adjustments to the

did not disrupt the all-important track gauge. The alignment of the track could be adjusted by shifting the sleepers bodily, without loss of gauge. Softwood was widely used, but its life was limited if it was not treated with preservative, and some railways set up creosoting plants for the purpose.

-treated hardwood is now widely used in North America and elsewhere. By now relatively long (perhaps 20 ft) wrought iron rails supported in chairs on timber cross-sleepers, were in use—a track form recognisable today in older track. Steel sleepers were tried as an alternative to timber; Acworth writing in 1889 describes the production of steel sleepers on the London & North Western Railway, and there is an illustration showing rolled channel section (shallow upturned "U" shapes) with no shaped ends, and with three-part forged chairs riveted direct. However steel sleepers seem not to have enjoyed widespread adoption until about 1995. Their dominant usage now is for life extension of existing track on secondary routes. They have a significant advantage on weak formations and poor ballast conditions, as the bearing area is at a high level, immediately under the rail seat.

Rail fastenings

The early cast iron rails of the 18th century and before used integral fixings for nailing or bolting to the railroad ties. Strap rails introduced in the late 18th century, of cast and later rolled iron were nailed to wooden supports via countersunk holes in the metal. The introduction of rolled rail profiles in the 1820s such as the ''single flanged T parallel rail'' and later ''double flanged T parallel rail'' required the use of chairs, keys to hold the rail, and bolts or spikes to fix the chair. The ''flat bottomed rail'' invented by

Robert L. Stevens Colonel Robert Livingston Stevens (October 18, 1787 – April 20, 1856) was an American inventor and steamship builder who served as president of the Camden and Amboy Railroad in the 1830s and 1840s. Early life Stevens was born in Hoboken, New ...

in 1830 was initially spiked directly to wooden sleepers, later tie plates were used to spread the load and also keep the rail in gauge with inbuilt shoulders in the plate. Outside North America a wide variety of spring based fastening systems were later introduced in combination with baseplates and flat bottomed rail, these are now ubiquitous on main line high speed railways.

Ballast

Track was originally laid directly on the ground, but this quickly proved unsatisfactory and some form of ballast was essential to ensure good drainage, spread the load and retain the track in position. The natural ground is rarely strong enough to accept the loading from locomotives without excessive settlement, more so in wet conditions; a layer of ballast under sleepers reduces the bearing pressure on the ground, tends to keep them in place and resist displacement, and keeps the permanent way well-drained. Ballast in early days was usually locally available mineral product, such as gravel or reject material from coal and iron mining. The

Great North of Scotland Railway The Great North of Scotland Railway (GNSR) was one of the two smallest of the five major Scottish railway companies prior to the 1923 Grouping, operating in the north-east of the country. Formed in 1845, it carried its first passengers the fro ...

used rounded river gravel, which does not constrain movement as much as sharp-edged stone. In later years slag, a by-product of steel making, and ash from steam locomotives was used. Modern practice is to employ sharp-edged stone crushed within a narrow size range.

Gauges

Early track gauges

The early railways were almost exclusively local concerns involved with conveying minerals to some waterway; for them the gauge of the track was adopted to suit the wagons intended to be used, and it was typically in the range 4 ft to 4 ft 8½ in, and at first there was no idea of the need for any conformity with the gauge of other lines. When the first public railways developed,

's skilful innovation meant that his railways were dominant and the gauge he used was therefore the most widespread. As early notions of linking up different railway systems evolved, this gauge secured general adoption. It is more or less an accident of history that this gauge—which suited the wagons already in use at the colliery where George Stephenson had been an engine man—became the British standard gauge: it was exported to most of Europe and North America. Reference is sometimes made to the "gauge" of ruts in stone roadways at ancient sites such as Pompeii, and these are often asserted to be about the same as Stephenson's gauge. Of course the ruts were made by the wheels of carts, and the carts were of a sensible size for horse-drawn carts prior to the industrial era, pretty much the same as the size of the pre-railway carts at the colliery where Stephenson worked: that is the only connection.

Broad gauge track

When

conceived the Great Western Railway (GWR), he sought an improved design for his railway track and accepted none of the previous received wisdom without challenge. The 4 ft 8½in gauge had been fine for small mineral trucks on a horse-drawn tramway, but he wanted something more stable for his high speed railway. The large diameter wheels used in stage coaches gave better ride quality over rough ground, and Brunel originally intended to have his passenger carriages carried in the same way—on large diameter wheels placed outside the bodies of the carriages. To achieve this he needed a wider track gauge and he settled on the famous broad gauge. (It was later eased to 7 ft 0¼in). When the time came to build the passenger carriages, they were designed conventionally with smaller wheels under the bodies after all, but with a seven-foot track gauge the bodies could be much wider than on the standard gauge. His original intention to have the wheels outside the width of the bodies was abandoned. Brunel also looked at novel track forms, and decided to use a continuously supported rail. Using longitudinal timbers under each rail, he achieved a smoother profile while not requiring such a strong rail section, and he used a shallow bridge rail for the purpose. The wider, flat foot also meant that the chair needed by the bullhead section could be dispensed with. The longitudinal timbers needed to be kept at the proper spacing to retain the gauge correctly, and Brunel achieved this by using timber transoms—transverse spacers—and iron tie-bars. The whole assembly was referred to as the

baulk road Baulk road is the name given to a type of railway track or 'rail road' that is formed using rails carried on continuous timber bearings, as opposed to the more familiar 'cross-sleeper' track that uses closely spaced sleepers or ties to give inte ...

—railwaymen usually call their track a road. Initially, Brunel had the track tied down to timber piles to prevent lateral movement and bounce, but he had overlooked the fact that the made ground, on which his track was supported between piles, would settle. The piles remained stable and the ground between them settled so that his track soon had an unpleasant undulation, and he had to have the piles severed, so that the track could settle more or less uniformly. A variant of the baulk road can still be seen today on many older under-bridges where no ballast was provided. The design varies considerably, but in many cases longitudinal timbers are supported directly on the cross-girders, with transoms and tiebars to retain the gauge, but of course with modern rails and base-plates or chairs. The longitudinal sleepers are somewhat similar to modern-day

Ladder track Ladder track is a type of railway track in which the track is laid on longitudinal supports with transverse connectors holding the two rails at the correct gauge distance. Modern ladder track can be considered a development of baulk road, which ...

. The group of railways that had Brunel as their engineer were successful and the broad gauge track spread throughout the west of England, South Wales, and the

West Midlands West or Occident is one of the four cardinal directions or points of the compass. It is the opposite direction from east and is the direction in which the Sun sets on the Earth. Etymology The word "west" is a Germanic word passed into some ...

. But, as the British railway network spread, the incompatibility of the two systems became a serious blockage, as a wagon could not be sent from one system to the other without transshipping the goods by hand. A Gauge Commission was appointed to determine national policy. The Broad Gauge was technically superior but conversion of the standard gauge routes to broad would have meant reconstructing every tunnel, bridge and station platform, whereas universal adoption of the standard gauge only required the progressive conversion of the track itself. The broad gauge was doomed, and no further independent broad gauge lines could be built. The existing broad gauge routes could continue, but as they had no development potential it was only a matter of time before they were eventually converted to standard. In the meantime, an extensive mileage of mixed gauge track was installed, where each line had three rails to accommodate trains of either gauge. There were some instances of ''mixed gauge trains'' being run, where wagons of each gauge were run in a single train. The legacy of the broad gauge can still be seen where there seems to be an unnecessarily wide space between station platforms.

Twentieth century and beyond

1900 to 1945

At the beginning of the twentieth century, the form of British track had converged on the use of

bullhead rails supported in cast iron chairs on timber sleepers, laid in some form of ballast. In North America, the standard was T-rails and tie plates fastened to timber crossties with cut spikes. Many railways were using very light rails and, as locomotive weights and speeds increased, these became inadequate. Consequently, on main lines, the rails in use were made progressively heavier (and stronger). Metallurgical processes improved and better rails, including some of steel, came into use. From a maintenance point of view, the rail joints were the source of most of the work, and as steel-making techniques improved it became possible to roll steel rails of increased length—reducing the number of joints per mile. The standard length became 30 ft (9 144mm), then 45 ft (13 716mm) and finally 60 ft (18 288mm) rails became the norm. For main line use, the standard rail section became the 95BH section, weighing 95 lb per yard (47.13 kg per metre). For secondary routes, a lighter 85BH (42.16 kg per metre) section was used. Flat bottom rails were still seen as undesirable for British main line railway use, despite their successful use in North America, although some lightly operated British railways used them, generally spiked direct to the sleepers. Under heavy usage, they indent the sleepers severely and the incremental cost of a base-plate appeared at this early date, to rule the flat bottom section out. Timber sleepers were expensive and not durable, and the railways’ engineers had strong—and conflicting—views about the best wood species and the best preservative treatments. The railways moved towards standardisation on a softwood sleeper preserved by pressure injection of

creosote Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics. Some creosote types were ...

, measuring 8 ft 6in (2 591 mm) long by 10in (254mm) by 5in (127mm). Chairs were secured to the sleepers by trenails (steel spikes driven through a timber sleeve) or three chair-screws on first class routes. The GWR alone among the main line railways kept to its own standard, the 00 rail at 97½ lb/yd (48.365 kg per metre), and with two fangbolts securing each chair to the sleeper, with the head of the bolt under the sleeper and a nut above the chair—more secure but much more difficult to adjust. Some experiments were made before 1945 with reinforced concrete sleepers, in most cases with bullhead chairs mounted on them. This was in response to the very high price of the best (most durable) timber, but reinforced concrete sleepers were never successful in main line use. Concrete pots were also used in sidings; they are sometimes called twin-block sleepers, and consisted of two concrete blocks each mounted with a chair, and an angle iron connecting them and retaining the gauge.

Post-war developments

At the end of the Second World War in 1945, the British railways were worn out, having been patched up following war damage without the availability of much new material. The country was economically in a weak situation also, and for nearly a decade after the war, materials—especially steel and

timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, w ...

—were in very short supply. Labour too was seriously restricted in availability. The railway companies became persuaded that the traditional bullhead forms of track needed revision, and after some experimentation a new flat bottom rail format was adopted. The

British Standard British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the a ...

sections were unsuitable and a new profile, a 109 lb/yard rail, was made the new standard. In 60 ft lengths, laid on steel baseplates on softwood sleepers, it was to be the universal standard. The fastenings were to be of a resilient steel type, and for secondary routes a 98 lb/yd rail was adopted. Regional variations still persisted, and hardwood sleepers and Mills clip fastenings were favoured on the Eastern Region, for example. The new designs were successful, but they introduced many challenges, especially as the availability of experienced track maintenance staff became acutely difficult, and poorly maintained flat bottom track seemed more difficult to keep in good order than poorly maintained bullhead track. The greater stiffness of flat-bottom was an advantage, but it tended to straighten out between the joints on curves; and flat bottom’s rigidity led to high vertical impact forces at badly maintained joints and this resulted in high volumes of fatigue fractures at the joints. Moreover, the elastic rail fastenings had little resistance to rail creep—the propensity of the rails to move gradually in the direction of traffic, and the workload of pulling back the rails to regulate the joints was surprisingly high.

Long welded rails

Much of the work of maintaining the track was at the joints, especially as the stiff rails became dipped, and the joint sleepers took a hammering. Pre-war experiments with long welded rail lengths were built upon, and in the years from 1960 long rail lengths were installed, at first on hardwood sleepers but soon on concrete sleepers. For example, the first long welded rail (almost ) on the UK's East Coast Main Line was laid in 1957, just south of

Carlton-on-Trent Carlton-on-Trent is a small village and civil parish in England, located between the River Trent and the A1 road near Newark-on-Trent in Nottinghamshire. The population of the civil parish was 228 at the 2001 census increasing marginally only to ...

, resting on rubber pads to resist rail creep. In this pioneering stage, some catastrophic mistakes in detailed design were made, but from about 1968 continuous welded rail became a reliable standard for universal installation on main and secondary routes. The form adopted used pre-stressed concrete sleepers and a 110A rail section—a slight improvement on the 109 rails previously used—the A was to distinguish it from the British Standard 110 lb/yd rail section, which was unsuitable. Rail fastenings eventually converged onto a proprietary spring clip made by the

Pandrol Pandrol is a global rail technology company, founded in 1953 and operating in over 100 countries worldwide, with over 400 railway systems having adopted its products. A member of the Delachaux Group, Pandrol is based in Colombes, France and ...

company which was the exclusive form of fastening in Britain for about 30 years. The welded track was to be laid on six to twelve inches (15 to 30 centimetres) of crushed stone ballast, although this was not always achieved, and the bearing capacity of the formation was not always taken into account, leading to some spectacular formation failures. A further enhancement to the rail profile produced the 113A section, which was the universal standard until about 1998; detail improvements to the sleepers and ballast profile completed the picture and the general form of the track had stabilised. This format is now in place over 99% of the first-class main lines in Britain, although the CEN60 (60 kg/m) rail section was introduced in the UK during the 1990s. This has a wider rail foot and is taller than the 113A section so is incompatible with standard sleepers.

Track renewal train A track renewal train (also known as a track renewal system or new track construction machine) is a work train that consists of many units of machinery and materials required for track renewal (rail and sleeper replacement) projects. Rail prepa ...

s have now replaced labour-intensive permanent way gangs. Long welded rail was hard to install manually. An early demonstration of mechanised track-laying with two lengths of long welded rail took place on the Fighting Cocks branch in 1958. The two lengths were loaded on ten wagons, attached to the existing track by a steel rope and drawn back at a minute. As the train moved back, the old rails were levered out and the new ones dropped into the chairs. A hoist on the rear wagon dropped the last part of the rail into place.

Track gauge

As stated, the general track gauge in Britain was . In the later 1950s, general track maintenance standards deteriorated rapidly due to labour shortages and, on some routes, faster freight train speeds. Freight trains consisted almost entirely of short wheelbase (10 ft) four-wheeled wagons carried on a very stiff elliptical leaf spring suspension, and these wagons showed a rapid rate of increase in derailments. In response to the dynamic behaviour ("hunting") of the wagons, the permitted speed of the wagons was reduced to 45 mph and, on new installations of continuously welded track on concrete sleepers, to reduce the track gauge by one-eighth of an inch to 4 ft 8⅜in (1432mm). In practice this change caused more problems than it cured and it was returned on renewals to 1435mm with effect from 1996. The gauge is set by the positioning of the cast-in fixings, so it is not a simple task to re-gauge existing track; it also creates problems with spot replacement of sleepers. Many sleepers were made with the reduced track gauge but standard gauge versions have also been manufactured in more recent times.

Switches and crossings

Terminology is difficult for "switches and crossings" (S&C) previously "points and crossings", or "fittings". Early S&C allowed only a very slow speed on the subsidiary route (the "turnout"), so geometrical design was not too important. Many older s&c units had a loose joint at the heel so that the switch rail could turn to close to the stock rail or open from it. When the switch rail was closed, a reasonable alignment was secured; when it was open, no wheel could run on it so it did not matter. As speeds rose, this was no longer feasible and the switch rails were fixed at the heel end, and their flexibility enabled the toe end to open and close. Manufacture of the switch rails was a complex process, and that of the crossings even more so. Speeds on the subsidiary route were rarely higher than 20 mph except in very special designs, and great ingenuity was employed to give a good ride to vehicles passing through at speed on the main line. A difficulty was the common crossing where continuous support to wheels passing was difficult, and the point rail was planed to protect it from direct impact in the facing direction, so that a designed irregularity in support was introduced. As faster speeds were required, more configurations of s&c were designed, and a very large number of components, each specific to only one type of s&c, was required. At faster speeds on the turnout road, the divergence from the main route is much more gradual, and therefore a very considerable length of planning of the switch rail is required. About 1971, this trend was reversed with the so-called vertical s&c, in which the rails were held vertical, rather than at the customary 1 in 20 inclination. With other simplifications, this considerably reduced the stockholding required for a wide range of s&c speeds, although the vertical rail imposes a loss of the steering effect and the ride through new vertical s&c is often irregular.

Continuous welded rail

Continuous Welded Rail (CWR) was developed in response to the observation that the bulk of track maintenance work takes place at the joints. As steel production and manufacturing processes improved, the rail lengths installed were progressively increased, and the logical extension of this would be to eliminate the joints altogether. A major obstacle to doing so is

thermal expansion Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of the average molecular kinetic ...

: the rails expand in higher temperatures. Without joints, there is no room for the rails to expand; as the rails get warmer, they will develop an enormous force in ''trying'' to expand. If prevented from expanding, they develop a force of 1.7 tonnes (17 kN) for every 1 degree Celsius of temperature change in a practical rail section.''General Instructions for the Installation and Maintenance of Continuous Welded Rail''; Civil Engineering Handbook No 11; British Railways; March 1988. If a small cube of metal is compressed between the jaws of a press, it will contract—that is it will be squashed somewhat—and a very large force can be resisted by it without ultimate failure. However, if a long piece of metal of the same cross section is compressed, it will deform sideways into a bow shape; the process is called buckling, and the compressive force it can withstand is very much less. If the long thin piece of metal could be constrained to prevent it from buckling (e.g. by being contained inside a tube) then it can resist a much higher compressive force. If the rails can be constrained in a similar way, they can be prevented from buckling. The weight of the track resists buckling upwards, so buckling is most likely to take place laterally. This is prevented by: * providing heavy sleepers, that generate friction on the ballast bed * ensuring that the sleepers are well supported on consolidated ballast to enable the generation of the friction * providing consolidated ballast around the sides of the sleepers to provide additional friction * heating the rails when they are installed and fastened in cool or cold weather, so that the expansion on the hottest days is less than otherwise * making sure that any rail added if rail breaks during cold weather is removed before warm weather returns. * making sure that curves do not line themselves inward during cold weather sufficiently to make buckling more likely when warm weather returns * taking precautions when track maintenance work is performed in hot weather, and making sure ballast is sufficiently consolidated before full-speed operation is resumed. If the rail is held so that it cannot expand at all, then there is no limit on the length of rail that can be handled. (The expansive force in a one-foot length of rail at a certain temperature is the same as in a mile or 100 mile length of rail.) Early continuous welded rail was installed in limited lengths only because of technological limitations. However at the end of the CWR section where it abutted older, ordinary jointed track, that track would be unable to resist the expansive force and the jointed track might be forced to buckle. To prevent that, special expansion switches, sometimes called breathers, were installed. The expansion switches could accommodate a considerable expansive movement—typically four inches (100mm) or so—in the end section of the CWR without passing the movement on to the jointed track. The CWR is installed and fastened down at an optimum temperature, to ensure that the highest possible expansive force is limited. This temperature is called the stress-free temperature, and in the UK it is . It is in the upper range of ordinary outdoor temperatures, and the actual installation work tends to be done at cooler temperatures. Originally the rails were physically heated to the stress-free temperature with propane gas heaters; they were then rattled with hand bars to eliminate any binding, preventing even expansion, and then clipped down. Since about 1963 however hydraulic jacks are used to physically stretch the rails while they are supported on temporary rollers. By stretching the rails to the length they would be if they were at the stress-free temperature, then there is no need to heat them; they can just be clipped down before the jacks are released. The CWR rails are made by welding ordinary rails together. For many years, rails could only be made in lengths of up to 60 ft (18m 288mm) in Britain, and the factory welding process made them into 600, 900 or 1200 ft lengths, depending on the factory. The process used was a flash-butt process in which high electrical currents are used to soften the rail end, and the ends are then forced together by rams. The flash-butt process is very reliable, providing that the factory ensured good geometry of the rail ends. The long rails could be conveyed to site by a special train, and unloaded on to the ground (by chaining the end in position and pulling the train out from underneath the rails). The long rails had to be welded together (or to adjacent track) using a site welding process; and, after initial experimentation, the proprietary

Thermit Thermite () is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create br ...

welding process was used. This was an alumino-thermic process in which a powder 'portion' was ignited; the

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

was the fuel and a metallurgically appropriate composition of molten steel descended into the gap between the rail ends, contained in refractory moulds. The original SmW process was very sensitive to operator skill, and as the welding was usually the final process before returning the track to traffic, time pressure was sometimes applied resulting in unwanted improper welds. The improved SkV process was less sensitive and over the years weld quality improved.Key, A. J., Frederick C. O. and Round D. J. (1983). "Thermit Rail Welding Development on British Rail". In: ''Rail Technology''. British Rail. . The issue of buckling is not restricted to CWR, and jointed track has suffered buckles in the past. The fish-plates at joints need to be removed and greased annually (the requirement was relaxed to bi-annually in 1993) and where this was omitted or where ballast conditions were especially weak, buckling took place in hot weather. In addition, if rails were allowed to creep, it was always possible that several successive joints might close up, so that the expansion gap was lost, with inevitable results at the onset of hot weather.

References

Sources

* {{DEFAULTSORT:Permanent Way h History of rail transport