LAYOUT AND CONSTRUCTION OF RAILWAY TRACK Introduction: Track Track is the base upon which the railway runs. To give a train a good ride, the track alignment must be set to within a millimeter of the design. Track design and construction is part of a complex and multi-disciplinary engineering science involving earthworks, steelwork, and timber and suspension systems - the infrastructure of the railway. In simple simple words words the track track of rai railw lway ay or rail railro road ad,, also known as the the perm perman anen entt way, way, is the the stru struct ctur ure e cons consis isti ting ng of the the ra rail ils, s, fasteners, railroad (sleepers and ballast ballast (or (or slab track, plus the underlying subgrade subgrade..
!ackground: The track is a fundamental part of the railway infrastructure and repr re pres esen ents ts the the prim primary ary dist distin inct ctio ion n betw betwee een n this this form form of land land transportation and all others in that it provides a "xed guidance system.
!asic construction: Track Track is the most obvious part of a railway route but there is a sub-structure supporting the track which is e#ually as important in ensu ensuri ring ng a safe safe and and comf comfor orta tabl ble e ride ride for for the the trai train n and and its its passengers or freight. The infrastructure diagram here here shows the principal parts of double-track line. The total width across the two-track alignment will be about $% m (%& ft for a modern formation. formation. The 'cess' shown shown each side of the
alignment is the area available for a walkway or refuge for sta working on the track.
The )ub-)tructure: This part of the road consists of three main elements* the formation, the sub-ballast and the ballast. The formation is the ground upon which the track will be laid. It can be the natural ground level or 'grade' or it can be an embankment or cutting. It is important that the formation is made of the right materials and is properly compacted to carry the loads of passing trains. The formation under the track has a 'camber' rather like that seen on a roadway. This is to ensure ease of water run-o to the drains provided on each side of the line. The track itself is supported on 'ballast', made up of a stone - usually granite below which is a layer of sand, which separates it from the formation.
!allast: !allast is provided to give support, load transfer and drainage to the track and thereby keep water away from the rails and sleepers. !allast must support the weight of the track and the considerable cyclic loading of passing trains. Individual loads on rails can be as high as %& tons (%% +) or short tons and around & short tons on a heavy haul freight line.
!allast is made up of stones of granite or a similar material and should be rough in shape to improve the locking of stones. In this way they will better resist movement. !allast stones with smooth edges do not work so well. !allast will be laid to a depth of to $ inches (up to /&& mm on a high speed track. !allast weighs about $,0&& to $,&& kg1cu1m. )ee also !allasted vs 2on!allasted Track below.
Track: The usual track form consists of the two steel rails, secured on sleepers so as to keep the rails at the correct distance apart (the gauge and capable of supporting the weight of trains. There are various types of sleepers and methods of securing the rails to them. )leepers are normally spaced at 0%& mm (% I2) to 30& mm (/& I2) intervals, depending on the particular railway4s standard re#uirements.
)leepers: Traditionally, sleepers are wooden. They can be softwood or hardwood. 5ost in softwood, although 6ondon +nderground uses a hardwood called 789arrah88 wood. )leepers are normally impregnated with preservative and, under good conditions, will last up to % years. They are easy to cut and drill and used to be cheap and plentiful. 2owadays, they are becoming more expensive and other types of materials have appeared notably concrete and steel.
;;<=2 >;2>?=T= )6==@=?) >oncrete is the most popular of the new types. >oncrete sleepers are much heavier than wooden ones, so they resist movement better.
?ail: The standard form of rail used around the world is the 'Aat bottom' rail. It has a wide base or 'foot' and narrower top or 'head'. The other one type of rail is a '!ullhead' rail and is shown in comparison with the standard type in the diagram left. !ullhead rail was originally designed with reuse in mind. It was intended that it would be turned over when the top had worn but this proved impossible because the underside also wore where it had been secured to the sleeper. !ullhead rail has to be mounted in a special 'chair' made of cast iron and secured by a 'key' wedged between the rail web and the chair. The chairs are secured to the sleepers by 'coach screws'. The arrangement can be seen in the "rst photo below:
Blat bottom rail !ullhead ?ails
The second photo above shows a Aat bottom rail clipped to a baseplate under the rail. Blat bottom rails can also be 'spiked' directly to the sleepers. 2ormally, the rail rests on a cast steel plate which is screwed or bolted to the sleeper. The rail is attached to the plate by a system of clips or clamps, depending on the design. The rail weight varries from &-& lb1yd. (pounds1yard in small yards to $&&-$$& lb1yd on light duty track and between $/& and $C$ lbs on heavy duty track. ?ail of $C$ lbs is the new main line standard.
?ail elding: 5odern track work uses long welded rail lengths to provide a better ride, reduce wear, reduce damage to trains and eliminate the noise associated with rail Doints. ?ail welding is a complex art depending on how you feel about it. There are two main types of welding used for rails: Thermite welding and Blash !utt welding.
Eauge: The standard track gauge - the distance between the two rails - is C ft. F in or $C/% mm. but many other gauges, wider and narrower than this, are in use around the world. Eauge is often intentionally widened slightly on curved track.
5odern Track Borms: There are now a range of modern track forms using a concrete base. They are generally used in special locations such as tunnels or bridges where a rigid base is re#uired to ensure track stability in relation to the surrounding structures. This type of track, usually called 'slab track' or 'non-ballasted' track.
!allasted vs 2on-!allasted Track: The basic argument for dierent track designs will be based on the bottom line - cost* cost of installation and cost of maintenance. There are however, other issues such as environment - noise, dust and vibration - or engineering issues such as space, location, climate and the type of service intended for the track. There are a wide variety of track forms and systems incorporating some form of concrete base or support which doesn4t need ballast. Glmost all of these re#uire less depth of construction than ballasted track. However, the accuracy of installation must be higher than that needed for ballasted track. )lab track will not be adDusted after installation but ballast can be packed to align track as re#uired.
)tructures: To ensure that the path re#uired for the passage of trains is kept clear along the route of a railway, a 'structure gauge' is imposed. This has the eect of forming a limit of building inside which no structures may intrude. The limit includes not only things like walls, bridges and columns but also pipes, cables, brackets and signal posts.
Eauging: The line of route has to be checked from time to time to ensure that the structures are not interfering with the gauge. G line is always gauged when a new type of rolling stock is to be introduced. It is important to see that the small variations in track position, platform edge, and cable duct location and signal e#uipment hasn4t been allowed to creep inwards during maintenance and renewal programmers. Eauging used to be done by hand locally (and still is from time to time in special circumstances but now a day, it is mostly done with a special train.
5onuments and
>urves: >urves in the track are almost a science on their own. >areful calculations are re#uired to ensure that curves are designed and maintained properly and that train speeds are allowed to reach a reasonable level without causing too much lateral stress on the track. There are both vertical curves and horiontal curves. There is also a section of track on either side of a curve known as the transition, where the track is changing from straight to a curve or from a curve of one radius to one of another radius.
>ant >ant is the name used to describe the cross level angle of track on a curve, which is used to compensate for lateral forces generated by the train as it passes through the curve. In eect, the sleepers are laid at an angle so that the outer rail on the curve is at a higher level than the inner rail. It is known as super elevation. >ant is measured either in degrees or in linear dimensions. ;n standard gauge track ($C/% mm or Cft. Fins. $%& mm or 0 ins. of cant is e#ual to 0 degrees. The maximum amount of cant de"ciency allowed is $$& mm (CF I2)..
Turnouts: e have used the word 'turnout' to describe the Dunctions in track work where lines diverge or converge. In the railway 'trade', turnouts are referred to as 'switch and crossing work'.
>rossings: The crossing can be cast or fabricated. ?ails are usually made of steel with large iron content but a little manganese is added to
crossings and some heavily used rails to increase resistance to wear.
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Construction Procedure of Railwa Trac! 2otwithstanding modern technical developments, the overwhelmingly dominant track form worldwide consists of Aatbottom steel rails supported on timber or pre-stressed concrete sleepers , which are themselves laid on crushed stone ballast. 5ost railroads with heavy traJc use continuously welded rails supported by sleepers attached via baseplates which spread the load. G plastic or rubber pad is usually placed between the rail and the tie plate where concrete sleepers are used. The rail is usually held down to the sleeper with resilient fastenings, although cut spikes are widely used. Bor much of the &th century, rail track used softwood timber ties and Dointed rails. The rails were typically of Aat bottom section fastened to the ties with dog spikes through a Aat tie plate and typically of bullhead section carried in cast iron chairs in practice.
9ointed rails were used, at "rst because the technology did not oer any alternative. However the intrinsic weakness in resisting vertical loading results in the ballast support becoming depressed and a heavy maintenance workload is imposed to prevent unacceptable geometrical defects at the Doints.
Track bed and foundation: ?ailway tracks are generally laid on a bed of stone track ballast or track bed, in turn is supported by prepared earthworks known as the track formation. The formation comprises the subgrade 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 the permanent way. The term foundation may be used to refer to the ballast and formation, i.e. all man-made structures below the tracks. The sub-grade layers are slightly sloped to one side to help drainage of water. ?ubber sheets may be inserted to help drainage and also protect iron bridgework from being aected by rust. Typical =xample of 6aying the @ermanent ay laying the track - known in railway terminology as the '@ermanent ay' - is an operation, which re#uires traditional engineering skills, much physical labor and specialied e#uipment. G bed of limestone known as 'ballast' is spread along the route of a depth of %-0 inches. =ach panel is physically aligned on top of this ballast and then bolted into position, end to end, connected by Aat plates known as '"shplates'.
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LAYOUT AND CONSTRUCTION OF RAILWAY STATION Introduction: G railway station is a place where trains make scheduled stops. )tations usually have one or more platforms constructed alongside a line of railway. However, railway stations come in many dierent con"gurations M inAuenced by such factors as the geographical nature of the site, or the need to serve more than one route, which may or may not be connected, and the level of the tracks. It should therefore be well designed, comfortable and convenient for the passenger as well as eJcient in layout and operation. )tations must be properly managed and maintained and must be operated safely.
)tation and >rossing )afety: There are two diering views about passenger safety at stations which have dictated station design for the last $%& years or more. Bor most of the world, it has been assumed that passengers (and other members of the public will take care of their own safety when walking on or near a railway. !ecause of this, it is not considered necessary to segregate passengers from trains. @assengers will look out for passing trains when crossing tracks and will take care not to leave luggage, children, cars or anything else which could damage or be damaged by a train. )tation design has reAected this so that platforms were often not raised very much above rail level.
@latforms: The term platform is worth explaining. The position of a train in a station is referred to as the 'track', as in.!ritish way of referring to the 'Train at @latform C', referring to the platform 'face', sometimes confuses foreign visitors, who see two trains, one on each side of the platform. The rest of the world has generally had a train1station interface designed on the basis that the passengers step up into the train from a low level platform or even )traight o the ground. However, high platforms are now seen in many countries around the world.
@latform width is also an important feature of station design. The width must be suJcient to accommodate the largest numbers of passengers expected but must not be wasteful of space - always at a premium for station areas in expensive land districts of a city. The platform should be designed to give free visual areas along its length so that passengers can read signs and sta can ensure safety when dispatching trains. @latform edges should be straight to assist operations by allowing clear sight lines.
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@latform screens and windows: There has been a trend recently in modern metro systems towards incorporating glaed screens along platform edges. This is only possible where sliding powered doors are available on trains and where the location of these doors is always consistent, which is why screen doors do not appear on main line railways. There are also local station door controls provided at the platform ends, in case the automatic system fails.
=ntrances and =xits: )tation entrances and exits must be designed to allow for the numbers of passengers passing through them, both under normal and emergency conditions. These codes usually de"ne the exit Aows and the types of exits allowed for, e.g. the dierent rates for passages, stairways and escalators. hatever the codes de"ne,
the entrances to a station must be welcoming to the prospective passenger. )tations must also have suJcient entrances to cater for the dierent sides of the railway route but the number must also take into account the cost eectiveness of each entrance. The cost of staJng ticket oJces can be very considerable and the numbers of ticket oJces must be managed to suit the patronage oering.
@assenger Information: Information system on stations is variously referred to as a @assenger Information )ystem (sometimes referred to as @I) or @assenger Information
The time now
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The destination and expected time of arrival of the next train
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The stations served by this train
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5aDor connections re#uiring boarding of this train The position of their car - if travelling with a reserved place here the train will stop - for variable length trains ;ther destinations served from this station and from which platform
Toilets: Bor a long time the provision of toilets on railway premises has been the subDect of criticism and debate, both in the industry and amongst passengers. @assengers expect to be provided with facilities and complain loudly when they are not. ;n the other hand, public toilets are regularly abused and vandalied in many countries and railway administrations end up paying large amounts to maintain and repair them. 2ow a day, it is considered good marketing to provide good restroom, baby changing and toilet facilities. They will not be cheap to provide and they will re#uire regular inspections to ensure the safety and cleanliness of the premises.
>oncessions: >oncessions on railway premises can be a lucrative source of income for a railway and the opportunity to provide for them should be taken wherever possible. The normal types of concessions are coee shops, refreshment counters and small lunch rooms, dry cleaners, newspaper shops and Aower shops. )hops should not be allowed to sell dangerous goods and may be restricted in the sale of tobacco products if the railway has a no smoking policy. )ome operators have excluded the sale of food within their property because they have a no eating1drinking policy.
)tation
)ignals:
&th century, signals were generally standardied, but with some variations in style and appearance.
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?eferences: $-
http:11www.railway-technical.com1stations.shtml http:11www.railway-technical.com1track.shtml
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http:11en.wikipedia.org1wiki1?ailwayNstationNlayout
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http:11en.wikipedia.org1wiki1GdelaideNrailwayNstation
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http:11en.wikipedia.org1wiki1?ailNtransport
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https:11www.#OlayoutPprocedurePofPrailwayPtrackQesNsm
3http:11vcxrivaleekdp.wordpress.com.train-layout-ho-for-salerandkey
