Layout and construction of a railway track and railway station

1
TOPIC

• Layout and construction of a railway track and
  railway station

2
RAILWAY 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, timber and suspension systems the
  infrastructure of the railway. 

3
Modern Track forms

• 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 required to ensure track
  stability in relation to the surrounding
  structures.  This type of track, usually called
  "slab track" or "non-ballasted" track

4
Ballasted vs Non-Ballasted Track

• The basic argument for different 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 doesn't need ballast.  Almost
  all of these require less depth of construction
  than ballasted track.  However, the accuracy of
  installation must be higher than that needed for
  ballasted track.  Slab track will not be adjusted
  after installation but ballast can be packed to
  align track as required.

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Elements of railway track

• Railway track consists of the following elements
• (1) Sub-structure
• Track is the most obvious part of a railway
  rout but there is a sub-structure supporting the
  track which is equally as important in ensuring a
  safe and comfortable ride for the train and its
  passengers. This part of the road consists of two
  main elements,
• Formation
• Ballast

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Elements of railway track

• Formation
• 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.
  It provides a smooth and uniform bed on which the
  track is laid.

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Elements of railway track

• Ballast
• The track itself is supported on "ballast",
  made up of stones usually granite or in the US,
  basalt below which is a layer of sand, which
  separates it from the formation. Ballast is
  provided to give support, load transfer and
  drainage to the track and there by keep water
  away from the rails and sleepers.  Ballast must
  support the weight of the track and the
  considerable cyclic loading of passing trains. 
  Ballast is made up of stones of granite.  Ballast
  will be laid to a depth of 9 to 12 inches .

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Elements of railway track

• 2- Sleepers
• Traditionally, sleepers (known as ties in the
  US) are wooden are used transverse support
  for a railway to give stiffness to it. They can
  be softwood or hardwood. Most in the UK are
  softwood, although London Underground uses a
  hardwood called Jarrah wood

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Types of sleepers

• Depending upon the material used for their
  manufacture, the sleepers can be divided into the
  following categories
• Wooden sleepers
• Steel sleepers
• Cast iron sleepers
• Concrete sleepers

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Types of sleepers

• wooden sleepers
• Advantages
• Wooden sleepers are the ideal type of sleeper.
  Hence they are universally used.They can be
  softwood or hardwood. They are easy to cut and
  drill and used to be cheap and plentiful. They
  absorb shocks and vibrations better than other
  types of sleepers.

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Wooden sleepers

• Disadvantages
  They are easily
  liable to attack by vermin and weather. Hence
  their life is lesser than other type of sleepers
  and also susceptible to fire.
• Their maintenance cost is highest in
  comparison to other type of sleepers.Their useful
  life is short about 12 to 15 years.

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Concrete sleepers

• Concrete is the most popular of the new types .
  Concrete sleepers are much heavier than wooden
  ones, so they resist movement better.  They work
  well under most conditions but there are some
  railways which have found that they do not
  perform well under the loads of heavy haul
  freight trains.  They offer less flexibility and
  are alleged to crack more easily under heavy
  loads with stiff ballast.  They also have the
  disadvantage that they cannot be cut to size for
  turnouts and special trackwork. 

13
Steel sleepers

• Steel sleepers are also now used on more
  lightly used roads, but they are regarded as
  suitable only where speeds are 100 mi/h or
  less.it is more durable than other types of
  sleepers and its life peried about 35-40 years.
  It is not susceptible to vermin attack and fire
  and also easily manufectureable.But there are
  also demarits,such as It is liable to corrosion
  and Fittings required are greater in number.

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Elements of railway track

• 3- Rails
• Rail is an iron beam.it has a wide base or
  "foot" and narrower top or "head".  The UK
  introduced a type of rail which was not used
  elsewhere apart from a few UK designed
  railways.  This was known as "Bullhead" rail and
  is shown in comparison with the standard type in
  the diagram.

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Types of rails

• Rails can be classified into the following
  categories
• Bull headed rail
• Flat footed rail
• 
  
  

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Rail Welding

• Modern trackwork uses long welded rail lengths to
  provide a better ride, reduce wear, reduce damage
  to trains and eliminate the noise associated with
  rail joints.  Rail welding is a complex art (or
  science) depending on how you feel about it. 
  There are two main types of welding used for
  rails Thermit welding and Flash Butt welding. 

17
Gauging

• The line of route has to be checked from time to
  time to ensure that the structures are not
  interfering with the gauge.  A 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, cable duct location and signal equipment
  hasn't been allowed to creep inwards during
  maintenance and renewalprogrammes.
   

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Monuments and Datum Plates

• Along the line of route various locations are
  marked by a fixed post in the track or a plate on
  a near by structure to indicate the correct level
  or position of the track.  These are called
  monuments or datum plates.  Measurements are
  taken from these to confirm the correct position
  of the track.

19
Curves

• Curves in the track are almost a science on their
  own.  Careful calculations are required 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 or inducing a derailment. 
  There are both vertical curves and horizontal
  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.

20
Cant

• Cant 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 effect,
  the sleepers are laid at an angle so that the
  outer rail on the curve is at a higher level than
  the inner rail.  In the US, it is known as
  superelevation. Cant is measured either in
  degrees or in linear dimensions.  On standard
  gauge track 150 mm or 6 ins. of cant is equal to
  6 degrees.   

21
Turnouts

• I have used the word "turnout" to describe the
  junctions in trackwork where lines diverge or
  converge so as to avoid "points" (UK) or
  "switches" (US).  A turnout consists of a number
  of parts as followsThe moving part of the
  turnout is the switch "blade" or "point", one for
  each route.  The two blades are fixed to each
  other by a tie bar to ensure that when one is
  against its stock rail, the other is fully clear
  and will provide room for the wheel flange to
  pass through cleanly.  Either side of the
  crossing area, wing and check rails are provided
  to assist the guidance of the wheelsets through
  the crossing.

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Types of turnouts

• There are a number of standard layouts or types
  of turnouts, as shown in the following diagrams.

23
Crossings

• The crossing can be cast or fabricated.  Rails
  are usually made of steel with a large iron
  content but a little manganese is added to
  crossings and some heavily used rails to increase
  resistance to wear.  Below is a photo of an
  example of a cast manganese crossing.  A crossing
  is also sometimes referred to as a "frog".

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Switch crossing

• A switched crossing (sometimes referred to as a
  swing nose crossing or moveable frog) will
  normally be provided for turnouts with a very
  acute angle.  The crossing will have a powered
  element which will be set for the required route
  at the same time as the switch blade is set.
• The blades of a turnout are normally moved
  remotely using an electrically operated point
  machine.  The machine contains the contacts which
  confirm the points are moved and locked in the
  correct position for the route set.  Point
  machines are normally located to one side of the
  track but a new generation of machines is now
  appearing where the mechanism is contained in a
  sleeper fitting between the rails.

25
Route Signalling

• Signalling in the UK has always used the
  principle of "route signalling" as opposed to the
  "speed signalling" philosophy adopted by European
  and US railways.  This means that drivers of a
  British train will be shown which route a train
  will take when it proceeds past a signal
  protecting a diverging junction. 

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RAILWAY STATION

• Introduduction
  There was a
  time (in the UK at least) when the word "station"
  would only ever be taken to refer to a railway
  station.  For some reason, nowadays people insist
  on referring to a station as a "train station as
  if there was any other sort of station.  
  Whatever it is called, the station can often be a
  neglected part of the railway scene but they are
  the usually first point of contact the passenger
  has with the system.

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Station

• Stations are the places where trains stop to
  collect and deposit passengers.  It should
  therefore be well designed, pleasing to the eye
  (photo left), comfortable and convenient for the
  passenger as well as efficient in layout and
  operation.  Stations must be properly managed and
  maintained and must be operated safely.

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Station and Crossing Safety

• There are two differing views about passenger
  safety at stations which have dictated station
  design for the last 150 years or more.  For most
  of the world, it has been assumed that passengers
  will take care of their own safety when walking
  on or near a railway.  Because of this, it is not
  considered necessary to segregate passengers from
  trains.  

29
Platforms

• The term platform is worth explaining.  In the
  US, the position of a train in a station is
  referred to as the "track" as in "The train for
  San Diego is on Track 9".   This is very logical
  as the raised portion of the ground next to the
  track is actually the platform and may well be
  used by passengers boarding a train on a track
  along the opposite edge of the platform.  For
  this reason, the British way of referring to the
  "Train at Platform 4", referring to the platform
  "face", sometimes confuses foreign visitors, who
  see two trains, one on each side of the
  platform. 

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Entrances and Exits

• Station entrances and exits must be designed to
  allow for the numbers of passengers passing
  through them, both under normal and emergency
  conditions.  Specific emergency exit requirements
  are outlined in many countries as part of safety
  legislation or to standards set down by the
  railways or other organisations. 

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Passenger Information

• Information systems on stations are variously
  referred to as a Passenger Information System
  (sometimes referred to as PIS) or Passenger
  Information Display (PID).  Professional railway
  staff often refer to them as Train Describers.  
  One of the most common complaints by passengers
  on railways is the lack of up to date and
  accurate information.  When asking the staff for
  information, passengers expect an accurate and
  courteous response with the latest data. 

32
Station Design

• The design of stations has developed over the
  years as the use of railways has first expanded
  and latterly declined.  A new form of station
  design has also evolved with the introduction of
  metros and high capacity urban railways. 
• On a railway which requires passengers to be in
  possession of a valid ticket or authority to
  travel whilst on the property, the station area
  is divided into an "unpaid area" and a "paid
  area", to denote the parts where passengers
  should be in possession of a valid ticket. 

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Side Platform Station

• The basic station design used for a double track
  railway line has two platforms, one for each
  direction of travel.  Each platform has a ticket
  office and other passenger facilities such as
  toilets and perhaps a refreshment or other
  concession. 

34
Island Platform Station

• A cheaper form of station construction, at least
  for a railway at grade level, is the island
  platform.  As its name suggests, this is a single
  platform serving two tracks passing on either
  side, effectively creating an island which can
  only be accessed by crossing a track.  A bridge
  or underpass is usually provided.  Island
  platforms are usually wider than single platforms
  used for side platform stations but they still
  require less area. 

35
Elevated Station with Side Platforms

• Elevated railways are still popular in cities,
  despite their history of noise creation and
  generally unfriendly environmental image.  The
  poor image has been considerably reduced with
  modern techniques of sound reduction and the use
  of reinforced and pre-stressed concrete
  structures.  They are considerably cheaper than
  underground railways and can be operated with
  reduced risk of safety. 

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Elevated Station with Ticket Hall Below
Platforms

• The ticket office and gate lines are below the
  platform level.  This can be done to allow one
  ticket office to serve both platforms but it
  requires the space to be available below track
  level and this, in turn, requires enough height
  in the structure.  Since many stations are built
  at road intersections, the location of the
  station structure might have to permit road
  traffic to pass beneath it and this requires an
  adequate height structure to be built.  It is
  sometimes better to position the structure to one
  side of the road intersection to allow room below
  for the ticket office.

37
Lifts and Escalators

• Vertical transportation at stations in city
  environments and on urban railways is almost as
  important as the horizontal transportation
  provided by the trains.  Any station not easily
  accessible on the surface and which requires
  stairs, will nowadays, require lifts for the
  disabled.  Stations with a height difference
  between levels of more than 4 to 5 metres will
  probably need escalators as well - certainly in
  the up direction.   

38
Junction signals

• This pair of stop signals protects a pair of
  diverging routes.  The lower signal is "off",
  indicating that the diverging route to the left
  of the two is set and locked and the train may
  proceed along that route.  The position of the
  two semaphore arms was often arranged so that one
  was lower than the other to indicate a slower
  route, usually because of a curve.

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Sources

• RAILWAY TRACK by Dan McNaughton, Simon Lowe and
  Mike Brotzman
• www.railway-technical.com/stations.shtml
• www.railway-technical.com/sigtxt1.shtml
• www.railway-technical.com/?
• Railway Age   Modern Railways  International
  Railway Journal  Railway Gazette International 
  Mass Transit  Trains Magazine.