Common contemporary practice in track construction, featuring well-drained ballast spread level with the tops of concrete sleepers/crossties – Australian National Railways, ca 1982
The first railway in Britain was theWollaton wagonway, built in 1603 between Wollaton and Strelley in Nottinghamshire. It used wooden rails and was the first of about 50 wooden-railed tramways built over the subsequent 164 years.[3] These early wooden tramways typically used rails of oak or beech, attached to wooden sleepers with iron or wooden nails. Gravel or small stones were packed around the sleepers to hold them in place and provide a walkway for the people or horses that moved wagons along the track. The rails were usually about 3 feet (0.91 m) long and were not joined - instead, adjacent rails were laid on a common sleeper. The straight rails could be angled at these joints to form primitive curved track.[3]
The first iron rails laid in Britain were at the Darby Ironworks inCoalbrookdale in 1767.[4]
Whensteam locomotives were introduced, starting in 1804, the track then in use proved too weak to carry the additional weight.Richard Trevithick's pioneering locomotive atPen-y-darren broke theplateway track and had to be withdrawn. As locomotives became more widespread in the 1810s and 1820s, engineers built rigid track formations, with iron rails mounted on stone sleepers, and cast-iron chairs holding them in place. This proved to be a mistake, and was soon replaced with flexible track structures that allowed a degree of elastic movement as trains passed over them.[3]
Section through railway track and foundation showing the ballast and formation layers. The layers are slightly sloped to help drainage. Sometimes there is a layer of rubber matting (not shown) to improve drainage, and to dampen sound and vibration
Traditionally, tracks are constructed using flat-bottomed steel rails laid on and spiked or screwed into timber or pre-stressed concrete sleepers (known as ties in North America), with crushed stoneballast placed beneath and around the sleepers.[5][6]
Most modern railroads with heavy traffic use continuously welded rails that are attached to the sleepers with base plates that spread the load. When concrete sleepers are used, a plastic or rubber pad is usually placed between the rail and the tie plate. Rail is usually attached to the sleeper with resilient fastenings, althoughcut spikes are widely used in North America. For much of the 20th century, rail track used softwood timber sleepers and jointed rails, and a considerable amount of this track remains on secondary and tertiary routes.
In North America and Australia,flat-bottomed rails were typically fastened to the sleepers with dog spikes through a flat tie plate. In Britain and Ireland,bullhead rails were carried in cast-iron chairs which were spiked to the sleepers. In 1936, theLondon, Midland and Scottish Railway pioneered the conversion to flat-bottomed rail in Britain, though earlier lines had made some use of it.[3]
Jointed rails were used at first because contemporary technology did not offer any alternative. However, the intrinsic weakness in resisting vertical loading results in the ballast becoming depressed and a heavy maintenance workload is imposed to prevent unacceptable geometrical defects at the joints. The joints also needed to be lubricated, and wear at the fishplate (joint bar) mating surfaces needed to be rectified by shimming. For this reason jointed track is not financially appropriate for heavily operated railroads.
Timber sleepers are of many available timbers, and are often treated withcreosote,chromated copper arsenate, or other wood preservatives. Pre-stressed concrete sleepers are often used where timber is scarce and where tonnage or speeds are high. Steel is used in some applications.
Track ballast is usually stone crushed to particular specifications. Its purpose is to support the sleepers and allow some adjustment of their position while allowing free drainage.
Traditional railway track showing ballast, sleepers, and rail fixings
Slab track with flexible noise-reducing rail fixings, built by German companyMax Bögl, on the Nürnberg–Ingolstadthigh-speed line
A disadvantage of traditional track structures is the heavy demand for maintenance, particularly surfacing (tamping) and lining to restore the desiredtrack geometry and smoothness of vehicle running. Weakness of the subgrade and drainage deficiencies also lead to heavy maintenance costs. This can be overcome by using ballastless track. In its simplest form this consists of a continuous slab of concrete (like a highway structure) with the rails supported directly on its upper surface (using a resilient pad).
There are a number of proprietary systems; variations include a continuous reinforced concrete slab and the use of pre-cast pre-stressed concrete units laid on a base layer. Many permutations of design have been put forward.
However, ballastless track has a high initial cost, and in the case of existing railroads the upgrade to such requires closure of the route for a long period. Its whole-life cost can be lower because of the reduction in maintenance. Ballastless track is usually considered for new very high speed or very high loading routes, in short extensions that require additional strength (e.g. railway stations), or for localised replacement where there are exceptional maintenance difficulties, for example in tunnels. Mostrapid transit lines andrubber-tyred metro systems use ballastless track.[7]
This type of track still exists on some bridges on Network Rail where the timber baulks are called waybeams or longitudinal timbers. Generally the speed over such structures is low.[12]
Later applications of continuously supported track includeBalfour Beatty's 'embedded slab track', which uses a rounded rectangular rail profile (BB14072) embedded in aslipformed (or pre-cast) concrete base (development 2000s).[13][14] The 'embedded rail structure', used in the Netherlands since 1976, initially used a conventional UIC 54 rail embedded in concrete, and later developed (late 1990s) to use a 'mushroom' shaped SA42 rail profile; a version for light rail using a rail supported in anasphalt concrete–filled steel trough has also been developed (2002).[15]
Modernladder track can be considered a development of baulk road. Ladder track utilizes sleepers aligned along the same direction as the rails with rung-like gauge restraining cross members. Both ballasted and ballastless types exist.
Modern track typically useshot-rolled steel with aprofile of an asymmetrical roundedI-beam.[16] Unlike some other uses ofiron andsteel, railway rails are subject to very high stresses and have to be made of very high-quality steel alloy. It took many decades to improve the quality of the materials, including the change from iron to steel. The stronger the rails and the rest of the trackwork, the heavier and faster the trains the track can carry.[citation needed]
North American railroads until the mid- to late-20th century used rails 39 feet (11.9 m) long so they could be carried ingondola cars (open wagons), often 40 feet (12.2 m) long; as gondola sizes increased, so did rail lengths.
According to theRailway Gazette International the planned-but-cancelled 150-kilometre rail line for theBaffinland Iron Mine, onBaffin Island, would have used oldercarbon steel alloys for its rails, instead of more modern, higher performance alloys, because modern alloy rails can become brittle at very low temperatures.[17]
Early North American railroads used iron on top of wooden rails as an economy measure but gave up this method of construction after the iron came loose, began to curl, and intruded into the floors of the coaches, leading early railroaders to refer to them as "snake heads".[18][19]
TheDeeside Tramway inNorth Wales used this form of rail. It opened around 1870 and closed in 1947, with long sections still using these rails. It was one of the last uses of iron-topped wooden rails.[20]
Rail is graded by itslinear density, that is, its mass over a standard length. Heavier rail can support greater axle loads and higher train speeds without sustaining damage than lighter rail, but at a greater cost. In North America and the United Kingdom, rail is graded in pounds per yard (usually shown aspound orlb), so130-pound rail would weigh 130 lb/yd (64 kg/m). The usual range is 115 to 141 lb/yd (57 to 70 kg/m). In Europe, rail is graded in kilograms per metre and the usual range is 40 to 60 kg/m (81 to 121 lb/yd). The heaviest mass-produced rail was 155 pounds per yard (77 kg/m), rolled for thePennsylvania Railroad.[citation needed]
The rails used inrail transport are produced in sections of fixed length. Rail lengths are made as long as possible, as the joints between rails are a source of weakness. Throughout the history of rail production, lengths have increased as manufacturing processes have improved.
The following are lengths of single sections produced bysteel mills, without anythermite welding. Shorter rails may be welded withflashbutt welding, but the following rail lengths are unwelded.
Welding of rails into longer lengths was first introduced around 1893, making train rides quieter and safer. With the introduction of thermite welding after 1899, the process became less labour-intensive, and ubiquitous.[26]
Newer longer rails tend to be made as simple multiples of older shorter rails, so that old rails can be replaced without cutting.[clarification needed] Some cutting would be needed as slightly longer rails are needed on the outside of sharp curves compared to the rails on the inside.[citation needed]
Rails can be supplied pre-drilled with boltholes forfishplates or without where they will be welded into place. There are usually two or three boltholes at each end.[citation needed]
Rails are produced in fixed lengths and need to be joined end-to-end to make a continuous surface on which trains may run. The traditional method of joining the rails is to bolt them together using metalfishplates (jointbars in the US), producingjointed track. For more modern usage, particularly where higher speeds are required, the lengths of rail may be welded together to formcontinuous welded rail (CWR).
Mainline, six-bolt rail joint on a segment of 155 lb/yd (76.9 kg/m) rail. The alternating bolt head orientation prevents joint separation should a derailed wheel strike the bolts. The electrical bonding jumper connects the two rails to maintaincontinuity of thetrack circuit.
Jointed track is made using lengths of rail, usually about 20 m (66 ft) long (in the UK) and 39 or 78 ft (12 or 24 m) long (in North America), bolted together using perforated steel plates known asfishplates (UK) orjoint bars (North America).
Fishplates are usually 600 mm (2 ft) long, used in pairs either side of the rail ends andbolted together (usually four, but sometimes sixbolts per joint). The bolts have alternating orientations so that in the event of aderailment and a wheelflange striking the joint, only some of the bolts will be sheared, reducing the likelihood of the rails misaligning with each other and worsening the derailment. This technique is not applied universally; European practice is to have all the bolt heads on the same side of the rail.
Small gaps which function asexpansion joints are deliberately left between the rail ends to allow for expansion of the rails in hot weather. European practice was to have the rail joints on both rails adjacent to each other; North American practice is to stagger them. Because of these small gaps, when trains pass over jointed tracks they make a "clickety-clack" sound, and in time the rail ends are deflected downwards. Unless it is well-maintained, jointed track does not have the ride quality of welded rail and is not suitable forhigh speed trains. However, jointed track is still used in many countries on lower-speed lines andsidings, and is used extensively in poorer countries due to the lower construction cost and the simpler equipment required for its installation and maintenance.
A major problem of jointed track is cracking around the bolt holes, which can lead to breaking of the rail head (the running surface). This was the cause of theHither Green rail crash which causedBritish Railways to begin converting much of its track to continuous welded rail.
Wheretrack circuits exist forsignalling purposes, insulated block joints are required. These compound the weaknesses of ordinary joints. Specially-made glued joints, where all the gaps are filled withepoxy resin, increase the strength again.
As an alternative to the insulated joint,audio frequency track circuits can be employed using atuned loop formed in approximately 20 m (66 ft) of the rail as part of the blocking circuit. Some insulated joints are unavoidable within turnouts.
Another alternative is anaxle counter, which can reduce the number of track circuits and thus the number of insulated rail joints required.
Welded rail jointA pull-apart on theLong Island Rail RoadBabylon Branch being repaired by using flaming rope to expand the rail back to a point where it can be joined together
Most modern railways usecontinuous welded rail, sometimes referred to asribbon rails orseamless rails. In this form of track, the rails arewelded together by utilisingflash butt welding to form one continuous rail that may be several kilometres long. Because there are few joints, this form of track is very strong, gives a smooth ride, and needs less maintenance; trains can travel on it at higher speeds and with less friction. Welded rails are more expensive to lay than jointed tracks, but have much lower maintenance costs. The first welded track was used in Germany in 1924.[33] and has become common onmain lines since the 1950s.
The preferred process of flash butt welding involves an automated track-laying machine running a strongelectric current through the touching ends of two unjoined rails. The ends become white hot due to electrical resistance and are then pressed together forming a strong weld.Thermite welding is used to repair or splice together existing continuous welded rail segments. This manual process requires a reaction crucible and form to contain the molten iron.
North American practice is to weld1⁄4-mile-long (400 m) segments of rail at a rail facility and load it on a special train to carry it to the job site. This train is designed to carry many segments of rail which are placed so they can slide off their racks to the rear of the train and be attached to the ties (sleepers) in a continuous operation.[34]
If not restrained, rails would lengthen in hot weather and shrink in cold weather. To provide this restraint, the rail is prevented from moving in relation to the sleeper by use of clips or anchors. Attention needs to be paid to compacting the ballast effectively, including under, between, and at the ends of the sleepers, to prevent the sleepers from moving. Anchors are more common for wooden sleepers, whereas most concrete or steel sleepers are fastened to the rail by special clips that resist longitudinal movement of the rail. There is no theoretical limit to how long a welded rail can be. However, if longitudinal and lateral restraint are insufficient, the track could become distorted in hot weather and cause a derailment. Distortion due to heat expansion is known in North America assun kink, and elsewhere as buckling. In extreme hot weather special inspections are required to monitor sections of track known to be problematic. In North American practice, extreme temperature conditions will trigger slow orders to allow for crews to react to buckling or "sun kinks" if encountered.[35] The German railway companyDeutsche Bahn is starting to paint rails white to lower the peak temperatures reached in summer days.[36]
After new segments of rail are laid, or defective rails replaced (welded-in), the rails can be artificially stressed if the temperature of the rail during laying is cooler than what is desired. Thestressing process involves either heating the rails, causing them to expand,[37] or stretching the rails withhydraulic equipment. They are then fastened (clipped) to the sleepers in their expanded form. This process ensures that the rail will not expand much further in subsequent hot weather. In cold weather the rails try to contract, but because they are firmly fastened, cannot do so. In effect, stressed rails are a bit like a piece of stretchedelastic firmly fastened down. In extremely cold weather, rails are heated to prevent "pull aparts".[38]
Continuous welded rails, complete with fastenings, are laid at a temperature known as "rail neutral temperature" that is approximately midway between the extremes experienced at that location. This installation procedure is intended to prevent tracks from buckling in summer heat or pulling apart in the winter cold. In North America, because broken rails are typically detected by interruption of the current in the signaling system, they are seen as less of a potential hazard than undetected heat kinks.
Joints are used in the continuous welded rail when necessary, usually for signal circuit gaps. Instead of a joint that passes straight across the rail, the two rail ends are sometimes cut at an angle to give a smoother transition. In extreme cases, such as at the end of long bridges, abreather switch (referred to in North America and Britain as anexpansion joint) gives a smooth path for the wheels while allowing the end of one rail to expand relative to the next rail.
A sleeper (tie or crosstie) is a rectangular object on which the rails are supported and fixed. The sleeper has two main roles: to transfer the loads from the rails to thetrack ballast and the ground underneath, and to hold the rails to the correct width apart (to maintain therail gauge). They are generally laid transversely to the rails.
Various methods exist for fixing the rail to the sleeper. Historically, rails were spiked directly on to ties, the practice giving way baseplates being fitted between the rails and sleepers; subsequently, spikes were replaced by sprung steel clips, such asPandrol clips, to fix the rail to the baseplates.
Sometimes rail tracks are designed to be portable and moved from one place to another as required. During construction of thePanama Canal, tracks were moved around excavation works. These track gauge were5 ft (1,524 mm) and the rolling stock full size. Portable tracks have often been used in open pit mines. In 1880 inNew York City, sections of heavy portable track (along with much other improvised technology) helped in the move of theancient obelisk in Central Park to its final location from the dock where it was unloaded from the cargo shipSS Dessoug.
Cane railways often had permanent tracks for the main lines, with portable tracks serving the canefields themselves. These tracks werenarrow-gauge (for example,2 ft (610 mm)) and the portable track came in straights, curves, and turnouts, rather like on a model railway.[39]
Decauville was a source of many portable light rail tracks, also used for military purposes.Thepermanent way is so called becausetemporary way tracks were often used in the construction of that permanent way.[40]
The geometry of the tracks is three-dimensional by nature, but the standards that express the speed limits and other regulations in the areas of track gauge, alignment, elevation, curvature and track surface are usually expressed in two separate layouts forhorizontal andvertical.
Horizontal layout is the track layout on thehorizontal plane. This involves the layout of three main track types:tangent track (straight line),curved track, andtrack transition curve (also calledtransition spiral orspiral) which connects between a tangent and a curved track.
Asidetrack is a railroad track other thansiding that is auxiliary to the main track. The word is also used as a verb (without object) to refer to the movement of trains and railcars from the main track to a siding, and in common parlance to refer to giving in to distractions apart from a main subject.[43] Sidetracks are used by railroads to order and organise the flow of rail traffic.
During the early days of rail, there was considerable variation in the gauge used by different systems, and in the UK during the railway building boom of the 1840s Brunel's broad gauge of7 ft 1⁄4 in (2,140 mm) was incompetition with what was referred to at the time as the 'narrow' gauge of1,435 mm (4 ft 8+1⁄2 in). Eventually the1,435 mm (4 ft 8+1⁄2 in) gauge won the battle, and became the standard gauge, with the term 'narrow gauge' henceforth used for gauges narrower than the new standard. As of 2017[update], about 60% of the world's railways use a gauge of1,435 mm (4 ft 8+1⁄2 in), known asstandard or international gauge[44][45] Gauges wider than standard gauge are calledbroad gauge; narrower,narrow gauge. Some stretches of track aredual gauge, with three (or sometimes four) parallel rails in place of the usual two, to allow trains of two different gauges to use the same track.[46]
Gauge can safely vary over a range. For example, U.S. federal safety standards allow standard gauge to vary from 4 ft 8 in (1,420 mm) to4 ft9+1⁄2 in (1,460 mm) for operation up to 60 mph (97 km/h).[47]
Circa 1917, an American section gang (gandy dancers) responsible for maintenance of a particular section of railway. One man is holding a lining bar (gandy), while others are using rail tongs to position a rail.Superelevation (cant) is clearly evident on the curve.
Track needs regular maintenance to remain in good order, especially when high-speed trains are involved. Inadequate maintenance may lead to a "slow order" (North American terminology, ortemporary speed restriction in the United Kingdom) being imposed to avoid accidents (seeSlow zone). Track maintenance was at one time hardmanual labour, requiring teams of labourers, or trackmen (US:gandy dancers; UK:platelayers; Australia: fettlers or packers) under the supervision of a skilled ganger, who used lining bars to correct irregularities in horizontal alignment (line) of the track, and tamping and jacks to correct vertical irregularities (surface). Currently, maintenance is facilitated by a variety of specialised machines.
Flange oilers lubricate wheel flanges to reduce rail wear in tight curves,Middelburg, Mpumalanga, South Africa
The surface of the head of each of the two rails can be maintained by using arailgrinder.
Common maintenance jobs include changing sleepers, lubricating and adjustingswitches, tightening loose track components, and surfacing and lining track to keep straight sections straight and curves within maintenance limits. The process of sleeper and rail replacement can be automated by using atrack renewal train.
Spraying ballast withherbicide to prevent weeds growing through and redistributing the ballast is typically done with a special weed killing train.
Over time, ballast is crushed or moved by the weight of trains passing over it, periodically requiring relevelling ("tamping") and eventually to be cleaned or replaced. If this is not done, the tracks may become uneven, causing swaying, rough riding and possibly derailments. An alternative to tamping is to lift the rails and sleepers and reinsert the ballast beneath. For this, specialist "stoneblower" trains are used.
Rail inspections utilizenondestructive testing methods to detect internal flaws in the rails. This is done by using specially equippedHiRail trucks, inspection cars, or in some cases, handheld inspection devices.
Rails must be replaced before the railhead profile wears to a degree that may trigger a derailment. Worn mainline rails usually have sufficient life remaining to be used on abranch line,siding orstub afterwards and are "cascaded" to those applications.
The environmental conditions along railroad track create a uniquerailway ecosystem. This is particularly so in the United Kingdom, where steam locomotives are only used on special services and vegetation has not been trimmed back so thoroughly. This creates a fire risk in prolonged dry weather.
In the UK, thecess is used by track repair crews to walk to a work site, and as a safe place to stand when a train is passing. This helps when doing minor work, while needing to keep trains running, by not needing a Hi-railer or transport vehicle blocking the line to transport crew to get to the site.
On this Japanese high-speed line, mats have been added to stabilize the ballast.
Railway tracks are generally laid on a bed of stonetrack ballast ortrack bed, which in turn is supported by prepared earthworks known as the track formation. The formation comprises thesubgrade and a layer of sand or stone dust (often sandwiched in impervious plastic), known as the blanket, which restricts the upward migration of wet clay or silt. There may also be layers of waterproof fabric to prevent water penetrating to the subgrade. The track and ballast form thepermanent way. The foundation may refer to the ballast and formation, i.e. all man-made structures below the tracks.
Some railroads are using asphalt pavement below the ballast in order to keep dirt and moisture from moving into the ballast and spoiling it. The fresh asphalt also serves to stabilize the ballast so it does not move around so easily.[48]
Additional measures are required where the track is laid overpermafrost, such as on theQingzang Railway inTibet. For example, transverse pipes through the subgrade allow cold air to penetrate the formation and prevent that subgrade from melting.
Geosynthetics are used to reduce or replace traditional layers in trackbed construction and rehabilitation worldwide to improve track support and reduce track maintenance costs.[49][50] Reinforcement geosynthetics, such asgeocells[51] (which rely on 3D soil confinement mechanisms) have demonstrated efficacy in stabilizing soft subgrade soils and reinforcing substructural layers to limit progressive track degradation. Reinforcement geosynthetics increase soil bearing capacity, limit ballast movement and degradation and reduce differential settlement that affects track geometry.[52] They also reduce construction time and cost, while reducing environmental impact and carbon footprint.[53] The increased use of geosynthetic reinforcement solutions is supported by new high-performance geocell materials (e.g., NPA -Novel Polymeric Alloy), published research, case studies projects and international standards (ISO,[54] ASTM,[55] CROW/SBRCURnet[56])
The hybrid use of high-performance geogrids at the subgrade and high-performance geocell in the upper subbase/subballast layer has been shown to increase the reinforcement factor greater than their separate sums, and is particularly effective in attenuating heaving of expansive subgrade clay soils.[57] A field test project onAmtrak's NE Corridor suffering clay mud-pumping demonstrated how the hybrid solution improved track quality index (TQI) significantly reduced track geometry degradation and lowered track surface maintenance by factor of 6.7x utilizing high-performance NPA geocell.[58] Geosynthetic reinforcement is also used to stabilize railway embankments, which must be robust enough to withstand repeated cyclical loading. Geocells can utilize recycled marginal or poorly graded granular material to create stable embankments, make railway construction more economical and sustainable.[59][60][61]
Some buses can use tracks. This concept came out of Germany and was calledO-Bahn [de]. The first such track, theO-Bahn Busway, was built in Adelaide, Australia.
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^Departments of the Army and the Air Force (8 April 1991).Railroad Track Standards(PDF). Washington, D.C. pp. 3-1 –7-4.{{cite book}}: CS1 maint: location missing publisher (link)
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^"Eleventh Annual Report (1848)",Annual report[s] of the Philadelphia, Wilmington and Baltimore Rail Road Company, vol. 4, pp. 17–20, 1842,archived from the original on 28 May 2016, retrieved20 November 2015
^Carolyn Fitzpatrick (24 July 2008)."Heavy haul in the high north".Railway Gazette International.Archived from the original on 1 May 2009. Retrieved10 August 2008.Premium steel rails will not be used, because the material has an increased potential to fracture at very low temperatures. Regular carbon steel is preferred, with a very high premium on the cleanliness of the steel. For this project, a low-alloy rail with standard strength and a Brinell hardness in the range of 300 would be most appropriate.
^PART 1025 Track Geometry (Issue 2 – 07/10/08 ed.). Department of Planning Transport, and Infrastructure - Government of South Australia. 2008.Archived from the original on 28 April 2013. Retrieved19 November 2012.
^Leshchinsky, B. (2011) Enhancing Ballast Performance using Geocell Confinement. Advances in Geotechnical Engineering, publication of Geo-Frontiers 2011 conference, Dallas, Texas, USA, March 13–16.
^Zarembski, Allan M.; Palese, Joseph; Hartsough, Christopher M.; Ling, Hoe I.; Thompson, Hugh (2017). "Application of Geocell Track Substructure Support System to Correct Surface Degradation Problems Under High-Speed Passenger Railroad Operations".Transportation Infrastructure Geotechnology.4 (4):106–125.Bibcode:2017TrIG....4..106Z.doi:10.1007/s40515-017-0042-x.S2CID256401992.
^ISO Standard WD TR 18228-5. (2018). Design using Geosynthetics – Part 5: Stabilization. International Organization for Standardization. Geneva, Switzerland. Under development.
^Vega, E., van Gurp, C., Kwast, E. (2018). Geokunststoffen als Funderingswapening in Ongebonden Funderingslagen (Geosynthetics for Reinforcement of Unbound Base and Subbase Pavement Layers), CROW/SBRCURnet, Netherlands. Publication C1001 (Dutch).
^Kief, O. (2016) Rail Track Pavements on Expansive Clay Restrained by Hybrid Geosynthetic Solution. Geosynthetics 2016 Conference Proceedings. Miami Beach, FL. April.
^Palese, J.W., Zarembski, A.M., Thompson, H., Pagano, W., and Ling, H.I. (2017). Life Cycle Benefits of Subgrade Reinforcement Using Geocell on a Highspeed Railway – a Case Study. AREMA Conference Proceedings (American Railway Engineering and Maintenance-of-Way Association). Indianapolis, IN, USA, September.
Winchester, Clarence, ed. (1936),"The permanent way",Railway Wonders of the World, pp. 331–338 illustrated description of the construction and maintenance of the railway
