CE 407

TRANSPORTATION ENGINEERING II

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 SYLLABUS
➢ Railway Engineering
➢ Introduction to Railways in India
➢ Geometric Design
➢ Railway Operation
➢ Railway Maintenance
➢ Railway Accidents
➢ Tunnel Engineering
➢ Harbours and Docks
Text Books:
➢ Railway Engineering by Saxena & Arora
➢ Railway Engineering by Rangwala
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➢ Harbour, Docks and Tunnel Engineering by R.Srinivasan
 MODULE 3
➢ Railway operation and control
❑Points and Crossings
❑Design features of a turnout
❑Details of station yards and marshalling yards
❑Signaling, interlocking of signals and points
❑Principles of track circuiting
❑Control systems of train movements - ATC, CTC

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 POINTS AND CROSSINGS
➢ Points and crossings are provided facilitates the change of railway vehicles from one track
to another
➢ The tracks may be parallel, diverging, or converging to each other
➢ The points or switches aid in diverting the vehicles and the crossings provide gaps in the
rails so as to help the flanged wheels to roll over them
➢ A complete set of points and crossings, along with lead rails, is called a turnout
➢ Turnout It is an arrangement of points and crossings with lead rails by means of which the
rolling stock may be diverted from one track to another
➢ https://youtu.be/rCY2u6rYtY0
➢ https://youtu.be/L8CmcNCMUto
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IMPORTANT TERMS

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Constituents of a turnout
 IMPORTANT TERMS
Name of the main
Various constituents of the assembly
assembly

A pair of stock rails, a pair of tongue rails, a pair of heel

Set of switches blocks, several slide chairs, two or more stretcher bars,
and a gauge tie plate

A nose consisting of a point rail and splice rails, two

Crossing
wing rails, and two check rails
Lead rails Four sets of lead rails 6
 IMPORTANT TERMS
➢ Direction of a turnout
✓ A turnout is designated as a right-hand or a left-hand turnout depending on whether it
diverts the traffic to the right or to the left
✓ The turnout is a right-hand turnout because it diverts the traffic towards the right side

Left hand turnout 7

 IMPORTANT TERMS
➢ Direction of a turnout

Left hand turnout 8

 IMPORTANT TERMS
➢ Direction of a turnout
✓ The direction of a point (or turnout) is known as the facing direction if a vehicle
approaching the turnout or a point has to first face the thin end of the switch
✓ The direction is trailing direction if the vehicle has to negotiate a switch in the trailing
direction, that is, the vehicle first negotiates the crossing and then finally traverses on the
switch from its thick end to its thin end
✓ Therefore, when standing at the toe of a switch, if one looks in the direction of the
crossing, it is called the facing direction and the opposite direction is called the trailing
direction

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 IMPORTANT TERMS
➢ Tongue rail
✓ It is a tapered movable rail, made of high-carbon or -manganese steel to withstand wear. At
its thicker end, it is attached to a running rail
✓ A tongue rail is also called a switch rail.
➢ Stock rail
✓ It is the running rail against which a tongue rail operates
➢ Points or switch
✓ A pair of tongue and stock rails with the necessary connections and fittings forms a switch
➢ Crossing
✓ It is a device introduced at the junction where two rails cross each other to permit the
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wheel flange of a railway vehicle to pass from one track to another
 IMPORTANT TERMS
➢ Three throw switch
• Two turnouts take off from the same point of main track
• Used in congested goods yard and entry points to
locomotive yards where there is much limitation of space
• It has two switches and each switch has two tongue rails
placed side by side
• Movement is possible in three different directions that is
straight, left and right

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 IMPORTANT TERMS
➢ Gathering lines
• A gathering line (also called a ladder track) is a track where a
number of parallel tracks gather or merge
• Alternatively, a number of parallel tracks also branch off from a
gathering line
• A gathering line is defined by the turnout angles and the angle of
inclination of the ladder track to the parallel tracks

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 SWITCHES

❑ A pair of stock rails, AB and CD, made of medium-manganese steel

❑ A pair of tongue rails, PQ and RS, also known as switch rails, made of medium-
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manganese steel to withstand wear
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 SWITCHES
❑The tongue rails are machined to a very thin section to obtain a snug fit with the stock rail
❑The tapered end of the tongue rail is called the toe and the thicker end is called the heel
❑A pair of heel blocks which hold the heel of the tongue rails is held at the standard
clearance or distance from the stock rails
❑A number of slide chairs to support the tongue rail and enable its movement towards or
away from the stock rail
❑Two or more stretcher bars connecting both the tongue rails close to the toe, for the
purpose of holding them at a fixed distance from each other
❑A gauge tie plate to fix gauges and ensure correct gauge at the points

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 SWITCHES - TYPES
➢ Two types – stub switch and split switch
➢ In a stub type of switch, no separate tongue rail is provided, and some portion of the track
is moved from one side to the other side
➢ Stub switches are no more in use on Indian Railways. They have been replaced by split
switches.
➢ Split switches consist of a pair of stock rails and a pair of tongue rails

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 SWITCHES - TYPES
➢Split switches may also be of two types-based on fixation at heel—loose heel type and fixed
heel type
❑Loose heel type: In this type, tongue rails are joined to lead rails by means of fish plates.
The two front bolts are kept loose to allow the throw of switch and these bolts are kept tight
when the tongue is open. This is suitable for short lengths switches (<6 m)

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 SWITCHES - TYPES
➢ Fixed heel type - Improvement of loose heel type. In this all the four bolts are tight when
the tongue is closed. It is used for long tongue rails (7 m to 25 m)

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 SWITCHES - TYPES
➢ Split switches may also be of three types based the toe of the switches
Undercut switch
❖Portion of flange at the foot of stock rail is cut to accommodate the tongue rail
❖This is used in Narrow gauge lines

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 SWITCHES - TYPES
Overriding switch
❖ In this case, the stock rail occupies the full section and the tongue rail is planned to a
6 mm (0.25") thick edge, which overrides the foot of the stock rail
❖Used for B.G and M.G tracks
❖ Stock rail of heavy section and Tongue rail of light section is used

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 SWITCHES - TYPES
Straight cut switch
❖ Tongue rail is cut in straight line with the stock rail
❖ This is done to increase the thickness of the toe of tongue rail, and hence the strength
❖ This is suitable for Bull headed rails
❖ A tongue rail may be either straight or curved.
❖ Straight tongue rails have the advantage that they are easily manufactured and can be used for
right-hand as well as left-hand turnouts.
❖ Straight rails are normally used for 1-in-8.5 and 1-in-12 turnouts on Indian Railways.

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 SWITCHES - TYPES
Straight cut switch
❖ Curved tongue rails are shaped according to the curvature of the turnout from the toe to the
heel of the switch.
❖ Curved tongue rails allow for smooth trains, but can only be used for the specific curvature for
which they are Curved switches are normally used for 1-in-16 and 1-in-20 IRS (Indian Standard)
turnouts on Indian Railways.
❖ Recently Indian Railways has also laying 1-in-8.5 and 1-in-12 turnouts with curved switches on
important

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 LENGTH OF TONGUE RAILS
➢ The length of a tongue rail from heel to toe varies with the gauge and the switch
➢ The longer the length of the tongue rail, the smoother the entry to the switch because of the smaller angle
the switch rail would make with the fixed heel divergence

Gauge and Length of tongue rail (mm)

type

1-in-8.5
1-in-12 straight 1-in-12 curved 1-in-16 Curved
straight

BG (90 R) 4725 6400 7730 9750 1.1150

MG (75 R) 4116* 5485* 6700

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CROSSING

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 CROSSING
➢ A crossing or frog is a device introduced at the point where two gauge faces across each
other to permit the flanges of a railway vehicle to pass from one track to another
➢ To achieve this objective, a gap is provided from the throat the nose of the crossing, over
which the flanged wheel glides or jumps
➢ In order to ensure that this flanged wheel negotiates the gap properly and does not strike
the nose, the other wheel is guided with the help of check rails
➢ Two rails, point rail and splice rail, which are machined to form a nose
➢ Point rail ends at the nose, whereas the splice rail joins it a little behind the nose
➢ Theoretically, the point rail should end in a point and be made as thin as possible, but
such a knife edge of the point rail would break off under the movement of traffic
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CROSSING

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CROSSING

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 CROSSING
➢ The point rail has its fine end slightly cut off form a blunt nose, with a thickness of 6 mm
➢ The toe of the blunt nose is called the actual nose of crossing (ANC) and the theoretical
point where the gauge faces from both sides intersect is called the theoretical nose of
crossing (TNC)
➢ Two wing rails consisting of a right-hand and a left-hand wing rail that converge to form a
throat and diverge again on either side of the nose.
➢ Wing rails are flared at the ends to facilitate the entry and exit of the flanged wheel in the
gap
➢ A pair of check rails to guide the wheel flanges and provide a path for them, thereby
preventing them from moving sideways, which would otherwise may result in the wheel
hitting the nose of the crossing as it moves in the facing direction. 29
CROSSING

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 TYPES OF CROSSING
➢ A crossing may be of the following types.
➢ On the basis of shape of crossing
❑ An acute angle crossing or 'V crossing
❑ An obtuse or diamond crossing.
❑ A square crossing
➢ On the basis of Assembly of crossing
❑ Spring or movable crossing
❑ Ramped crossing

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 TYPES OF CROSSING
❑ An acute angle crossing or 'V' crossing
• Widely used
• Obtained when a left-hand rail of one track crosses a right hand rail of another track or vice versa
• Angle of intersection of the approaching rail is acute angle

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 TYPES OF CROSSING
❑ An obtuse or diamond crossing
• Obtained when a left-hand rail of one track crosses a right hand rail of another track or vice
versa at an obtuse angle

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 TYPES OF CROSSING
❑A square crossing
• Two tracks cross at right angles. Such crossings are rarely used in actual practice

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 TYPES OF CROSSING
➢ Spring or moveable crossing
❑ One wing rail is movable and is held against the Vee of the crossing with a strong helical spring
❑ By doing so it makes the main track continuous and this crossing becomes very useful when
there is high speed traffic on main tracks and light speed traffic on a turnout
❑ In India, this is not in practice because there is a danger of accident in case of spring failure

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 TYPES OF CROSSING

➢ Ramped crossing
❑In case of complicated yard layout with heavy but slow speed traffic the throat to nose
clearance is negotiated by use of special manganese steel blocks over long distance
❑The wheel flanges roll over this distance extending from a little beyond the throat to little
beyond the nose
❑So the entire wheel load comes on the flange and this type of crossing may be used with
safety for slow speeds

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 NUMBER AND ANGLE OF CROSSING
❑ A crossing is designated either by the angle the gauge faces make with each other or, more commonly, by the
number of the crossing, represented by N
𝑆𝑝𝑟𝑒𝑎𝑑 𝑎𝑡 𝑡ℎ𝑒 𝑙𝑒𝑔 𝑜𝑓 𝑐𝑟𝑜𝑠𝑠𝑖𝑛𝑔
❑𝑁 =
𝑇ℎ𝑒 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑐𝑟𝑜𝑠𝑠𝑖𝑛𝑔 𝑇𝑁𝐶

❑ There are three methods of measuring the number of a crossing, and the value of N also depends upon the
method adopted
❑ Centre line method
➢ This method is used in Britain and the US. In this method, N is measured along the centre line of the crossing.

1 ∝
𝑁= cot( ) 37
2 2
 NUMBER AND ANGLE OF CROSSING
❑ Right angle method
➢ Used on Indian Railways
➢ N is measured along the base of a right-angled triangle
➢ Also called Coles method.

𝑁 = cot(∝)

❑ Isosceles triangle method

➢ N is taken as one of the equal sides of an isosceles triangle
➢ Used in tramways
1
𝑁 = ( )co𝑠𝑒𝑐(∝/2)
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 NUMBER AND ANGLE OF CROSSING
❑To determine the number of a crossing-on site, the point where the offset gauge face of
the turnout track is 1 m is marked.
❑The distance of this point (in metres) from the theoretical nose of crossing gives N.

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 TURNOUT DESIGN – IMPORTANT TERMS
❑There are two standard methods prevalent for designing a turnout.
(a) Coles method
(b) IRS method
❖Curve lead (CL) This is the distance from the tangent point (T) to the theoretical nose of
crossing (TNC) measured along the length of the main track.
❖Switch lead (SL) This is the distance from the tangent point (T) to the heel of the switch
(TL) measured along the length of the main track.
❖Lead of crossing (L) This is the distance measured along the length of the main track as
follows
Lead of crossing (L) = curve lead (CL) - switch lead (SL)
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 TURNOUT DESIGN – IMPORTANT TERMS
❖Gauge (G) - This is the gauge of the track.
❖Heel divergence (d) -This is the distance between the main line and the turnout side at
the heel.
❖Angle of crossing (∝) - This is the angle between the main line and the tangent of the
turnout line.
❖Radius of turnout (R) - This is the radius of the turnout. It may be clarified that the radius
of the turnout is equal to the radius of the centre line of the turnout plus half the gauge
width.
R = Ro+ 0.5G

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TURNOUT DESIGN – IMPORTANT TERMS

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 TURNOUT DESIGN

➢ A turnout, after branching off from the main track, may run into various directions of
which running parallel to the original track is most common
➢ The design calculation of various turnout are based on following three factors:
i. Method of calculating various leads
ii. Method employed for crossing angle
iii. Type of tongue rail used

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 TURNOUT DESIGN
Notation used in design calculation
❑ CL= Curve lead
❑ SL= Switch lead
❑ L = Lead or crossing lead
❑ β = Angle of the switch
❑ α = Angle of the crossing
❑ d = Heel divergence or clearance
❑ R0 = Radius of the outer turnout
❑ R = Radius of centre line of the turnout
❑ G = Gauge of the track
❑ N = Number of the crossing
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❑ D = Distance between T.N.C. and tangent point of crossing curve
 TURNOUT DESIGN – METHOD I (COLE’S METHOD) – DESIGN
CALCULATION
• Curvature starts at toe of switch and ends at TNC
• 3 kinks at toe, heel and distance block of crossing
❑ Curve lead (CL), CL= 2GN
❑ R-Radius, R = R0 – G/2 , R0 = 1.5G + 2GN2

❑ SL = 2 𝑅0 𝑑

❑ Lead or crossing lead (L), L = CL – SL= 2GN - 2 𝑅0 𝑑

𝑆𝐿2
❑ Heel Divergence (d) , d=
2 𝑅0

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 TURNOUT DESIGN – METHOD II – DESIGN CALCULATION
• Assumption that the curve is tangential to tongue rail
• Only two kinks are left, one at toe of switch and
other at TNC
𝛼+𝛽
❑ Lead or crossing lead (L), L = (G - d) cot
2
𝐺–𝑑
❑ R-Radius: R0 =
𝑐𝑜𝑠 𝛽 − 𝑐𝑜𝑠 𝛼

❑ R = R0 – G/2

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 TURNOUT DESIGN – METHOD III (IRS METHOD) – DESIGN
CALCULATION
• Curvature starts from heel of switch and ends at toe of crossing
• Only kink in layout is at toe of switch
𝛼+𝛽
❑Lead or crossing lead (L), L = x cos α + (G – d – x sinα) 𝑐𝑜𝑡
2
𝐺 −𝑑−𝑥 sin(𝛼)
❑R-Radius: R0 =
𝐶𝑜𝑠 𝛽 −𝑐𝑜𝑠𝛼

❑ R = R0 – G/2

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Problem: A turnout is to be laid off a straight BG track with a 1 in 12 crossing. Determine the lead
and radius of turnout with the help of following data: heel divergence = 133mm, crossing angle
4˚45’49”, switch angle 1˚8’0”, straight length between the theoretical nose of crossing and tangent
point of crossing = 1.418m.
Solution:
𝐺 −𝑑−𝑥 sin(𝛼) 1.676−0.133−(1.418×sin(4°45′ 49"))
R0 = = = 437.38 𝑚
𝐶𝑜𝑠 𝛽 −𝑐𝑜𝑠𝛼 cos(1°8′ 0")−cos(4°45′ 49")
𝐺 1.676
𝑅 = 𝑅0 − = 437.38 − = 436.542 𝑚
2 2
𝛼+𝛽 4°45′ 49"+1°8′ 0"
Lead or crossing lead, L = (G - d) cot = 1.676 − 0.133 × cot = 29.9 𝑚
2 2

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 STATION YARDS
➢ System of tracks laid out to deal with the passenger as well as goods traffic being
handled by the railways.
➢ This includes receipt and dispatch of trains apart from sorting, marshalling, and other
such functions
STATION YARDS - TYPES
Coaching yard
➢ The main function of a coaching yard is to deal with the reception and dispatch of
passenger trains
➢ Depending upon the volume of traffic, this yard provides facilities such as watering
and fuelling of engines, washing of rakes, examination of coaches, charging of
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batteries, and trans-shipment of passengers
 STATION YARDS
Goods yard
➢ A goods yard provides facilities for the reception, loading, unloading, and dispatch
of goods wagons
➢ No sorting, marshalling and reforming is done at goods yards except in the case of
'sick' wagons or a few wagons booked for that particular station
➢ Separate goods sidings are provided with the platforms for the loading and
unloading of the goods being handled at that station
Marshalling yard
➢ A goods yard which deals with the sorting of goods wagons to form new goods
trains
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 STATION YARDS
Locomotive yard
➢ This is the yard which houses the locomotive
➢ Facilities for watering, fuelling, examining locomotives, repairing, etc., are provided in
this yard
➢ Designed depending upon the number of locomotives required to be housed in the
locomotive shed
➢ The facilities are so arranged that a requisite number of locomotives are serviced
simultaneously and are readily available for hauling the trains
➢ Such yards should have adequate space for storing fuel
➢ The water supply should be adequate for washing the locomotives and servicing them
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 STATION YARDS
➢ Sick line yard
➢ Whenever a wagon or coach becomes defective, it is marked ‘sick’ and taken to sick
lines
➢ Yard deals with such sick wagons
➢ Adequate facilities are provided for the repair of coaches and wagons, which include
examination pits, crane arrangements, train examiner's office and workshop, etc.
➢ A good stock of spare parts should also be available with the train examiner for
repairing defective rolling stock

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 MARSHALLING YARD
➢ Yard where goods trains are received and sorted out, and new trains are formed and
finally dispatched to various destinations
➢ This yard receives loaded as well as empty goods wagons from different stations for
further booking to different destinations
➢ These wagons are separated, sorted out, properly marshalled, and finally dispatched
bearing full train loads to various destinations
➢ The empty wagons are kept in marshalling and the same can be supplied as and when
required by other stations

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 MARSHALLING YARD - FUNCTIONS

➢ Reception of trains: Trains are received in the reception yards with the help of various
lines
➢ Sorting of trains: Trains are normally sorted with the help of a hump with a shunting
neck and sorting sidings.
➢ Departure of trains: Trains depart from departure yards where various lines are
provided for this very purpose. Separate yards may be provided to deal with up and
down traffic as well as through trains, which need not be sorted out.

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MARSHALLING YARD - FUNCTIONS

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 MARSHALLING YARD – DESIGN PRINCIPLES
➢ A marshalling yard should be so designed that there is minimum detention of
wagons in the yard and as such sorting can be done as quickly as possible
➢ These yards should be provided with the necessary facilities such as a long shunting
neck, properly designed hump, braking arrangement in the shape of mechanical
retarders, etc., depending upon the volume of traffic
➢ The following points should be kept in mind when designing a marshalling yard
❑Through traffic should be received and dispatched as expeditiously as possible. Any
idle time should be avoided.
❑There should be a unidirectional movement of the wagons as far as possible

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 MARSHALLING YARD – DESIGN PRINCIPLES
❑There should be no conflicting movement of wagons and engines in the various parts of
the yard
❑ The marshalling yard should be provided with all facilities to place and withdraw wagons
from various points
❑The marshalling yard should be well lighted
❑The marshalling yard should be constructed at all important junction stations and
particularly on stations where main routes are converging
❑There should be adequate scope for the further expansion of the marshalling yard
❑All important portions of marshalling yard should be properly positioned

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 MARSHALLING YARD – TYPES
FLAT YARD
➢ All the tracks are laid almost level and the wagons are relocated for sorting is done with
the help of an engine
➢ This method is costly as it requires the constant use of locomotive power
GRAVITATIONAL YARD
➢ In this yard, tracks are laid at such a gradient, the wagons can move of their own under
the action of gravity
➢ The tracks are so laid that the wagons move to the siding assigned for the purpose of
sorting by the action of gravity
➢ Sometimes, shunting is done with the help of gravity assisted by engine power
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 MARSHALLING YARD – TYPES
HUMP YARD
➢ In this yard, an artificial hump is created by means of proper earthwork
➢ The wagons are pushed up to the summit of the hump with the help of an engine
from where they slide down and reach the sidings under the effect of gravity
➢ Speed regulation is done as follows
➢ Mechanical method: In this method, wagons are slowed down automatically with
the help of 'retarders'
➢ Retarders' normally in the shape of bars fixed on either side of the track, operate
electrically or electromechanically and resist the movement of wagons by pressing against
the sides of the moving wheels
➢ This finally stops the wagons at the appropriate place 63
 MARSHALLING YARD – TYPES
➢ Non -Mechanical method: In a non-mechanical yard, the speed of the wagon is
regulated manually with the help of hand brakes or skids.
➢ wagon applies a hand brake at an appropriate place, making the wagon slip and stop
➢ Skids are also used to slow down the wagons
➢ Skids are placed on the track; they get dragged by the rolling wagon and the friction
thus developed reduces the speed of the wagon and stops it at the desired location

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 SIGNALLING
➢ Signalling consists of the systems, devices and means by which trains are operated
efficiently and tracks are used to maximum extent, maintaining the safety of the
passengers, the staff and the rolling stock
➢ Includes the use and working of signals, points, block instruments and other
equipments
OBJECTIVES
➢ To regulate the movement of trains so that they run safely at maximum permissible
speeds
➢ To maintain a safe distance between trains those are running on the same line in the
same direction
➢ To ensure the safety of two or more trains that has to cross or approach each other
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➢ To provide facilities for safe and efficient shunting

 SIGNALLING
OBJECTIVES
➢ To regulate the arrival and departure of trains from the station yard
➢ To guide the trains to run at restricted speeds during the maintenance and repair of tracks
➢ To ensure the safety of the train when it comes in contact with road traffic at level crossings

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SIGNALLING - CLASSIFICATION

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 SIGNALLING – CLASSIFICATION – BASED ON OPERATING
CHARACTERISTICS
DETONATING SIGNAL
➢ Audible signals such as detonators and fog signals are used in
cloudy and foggy weather when hand or fixed signals are not visible
➢ Their sound can immediately attract the attention of drivers
➢ Detonators contain explosive material and are fixed to the rail by
means of clips
➢ In thick foggy weather, detonators are kept about 400 to500 m
ahead of a signal to indicate the presence of the signal to the
drivers
➢ Once the train passes over the detonators thereby causing them to
explode, the driver becomes alert and keeps a lookout for the
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signal so that he/she can take the requisite action
 SIGNALLING – CLASSIFICATION – BASED ON OPERATING
CHARACTERISTICS
HAND SIGNAL
➢ These signals are in the form of flags (red or green) fixed to wooden handles that are held by railway
personnel assigned this particular duty
➢ If the flags are not available, signalling may be done using bare arms during the day
➢ In the night, hand lamps with movable green and red slides are used for signalling purposes.
➢ Used by guards, Station masters, Cabin man, Gang man, Key man, Point man or authorised man
➢ Indications of hand signals
➢ Red flag or light – Stop
➢ Green flag or light –Proceed
➢ yellow- Proceed cautiously
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 SIGNALLING – CLASSIFICATION – BASED ON OPERATING
CHARACTERISTICS
FIXED SIGNAL
➢ These are firmly fixed on the ground by the side of the track and can be further subdivided into caution
indicators and stop signals.
Caution indicators
➢ Provided for communicating to the driver that the track ahead is not fit for the running the train at normal
speed
➢ These signals are used when engineering works are underway and are shifted from one place to another
depending upon requirement
Stop signals
➢ These are fixed signals that normally do not change their position. They inform the drivers about the
condition of the railway line lying ahead.
➢ The stop signals normally used on railways are semaphore signals, coloured light signals, and other such 70
signals as explained in subsequent sections.
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
STOP OR SEMAPHORE SIGNAL
CHARACTERISTICS
➢ The principle of design of semaphore signal is to
show the stop position of any failure that happens to
be in the apparatus
➢ It consists of a movable arm, weight and lever
arrangement, spectacle frame, a crank rod and a
ladder
➢ The arm of the semaphore signal on the side facing
the driver is painted red with a vertical white stripe
➢ The other side of the signal is painted white with a
black vertical stripe
➢ This is pivoted on the horizontal pin known as spindle
near top of the post
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➢
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
STOP OR SEMAPHORE SIGNAL
➢ The arm is 1.2m to 1.7m long, 23cm to 25cm wide at the inner edge and 25cm to 35cm wide at
the outer edge in normal position arm remains horizontal
➢ In order for the signal to also be visible at night, a kerosene oil or electric lamp, operated through
a twilight switch, is fixed to the post
➢ A spectacle is also attached to the moving signal arm, which contains green and red coloured
glasses
➢ The red glass is positioned at the upper end and the green glass is positioned at the lower end of
the spectacle so that the red light is visible to the driver when the arm is horizontal and the
green light is visible when the arm is lowered
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 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
STOP OR SEMAPHORE SIGNAL
➢ The semaphore signal can be used as a stop signal as
well as a warner signal
➢ A lever capable of revolving about horizontal pin is
provided
➢ At one end, a weight is attached and a crank rod is
connected to the lever through a cam to the other
end of lever, a wire is attached which is taken to
signal cabin after passing over pulleys

73
SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS

74
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
PERMISSIVE SIGNAL – WARNER OR DISTANT SIGNAL
➢ In order to ensure that trains speed up safely, it is considered necessary that warning be given to
drivers before they approach a stop signal
➢ This advance warning is considered necessary, otherwise the drivers may confront a 'stop signal'
when they least expect it and take abrupt action, which can lead to perilous situations
➢ A warner or distant signal has, therefore, been developed, which is to be used ahead of a stop
signal and is in the form of a permissive signal that can be passed even in most restricted
conditions
➢ In the case of a stop signal, the driver has to stop the train when it is in the 'on' position, but in the
case of a permissive signal, the driver can pass through even when it is in the 'on' position
75
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS

PERMISSIVE SIGNAL – WARNER OR DISTANT SIGNAL

➢ The most restrictive aspect of a permissive or warner signal is that the driver is not supposed to
stop at the signal even when it is in the ‘on’ position
➢ The warner signal is similar to a stop signal except that the movable arm is given the shape of fish
tail by providing a V-shaped notch at the free end; the white strip is also V-shaped
➢ It is painted yellow and exhibits a yellow or amber colour at night instead of red colour
➢ In the case of signalling using coloured light, the permissive signal is distinguished from the stop
signal by the provision of a P marker disc on the signal post

76
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
PERMISSIVE SIGNAL – WARNER OR DISTANT SIGNAL

77
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS

SHUNT SIGNAL
➢ These are miniature signals and are mostly used for regulating the shunting of vehicles in station
yards
➢ Unlike fixed signals, these are small in size and are placed on an independent post of a running
signal post
➢ In semaphore signalling areas, the shunt signals are of the disc type
➢ The disc type of shunt signal consists of a circular disc with a red band on a white background
➢ The disc revolves around a pivot and is provided with two holes, one for the red lamp and the
other for the green lamp, for the purpose of night indication
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 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
SHUNT SIGNAL
➢ At night, the 'on' position of the signal is indicated by the horizontal red band and the red light,
indicating danger
➢ During the day the red band inclined to the horizontal plane and during the night the green light
indicates that the signal is 'off'
➢ In colour light signalling areas, the shunt signal on an independent post consists of two white
lights forming a line parallel to the horizontal plane
➢ This indicates that the signal is 'on' or that there is danger ahead whereas two white lights
forming a line inclined to the horizontal plane indicate 'off' or that the train can proceed

79
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
COLOURED LIGHT SIGNAL
➢ These signals use coloured lights to indicate track conditions to the driver both during the
day and the night
➢ In order to ensure good visibility of these light signals, particularly during daytime, the light
emission of an electric 12-V, 33-W lamp is passed through a combination of lenses in such a
way that a parallel beam of focused light is emitted out
➢ This light is protected by special lenses and can be distinctly seen even in the brightest
sunlight
➢ The lights are fixed on a vertical post in such a way that they are in line with the driver's eye
level
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 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
COLOURED LIGHT SIGNAL
➢ The system of interlocking is so arranged that only one aspect is displayed at a time
➢ Coloured light signals are normally used in suburban sections and sections with a high
traffic density
❖ Two-aspect -green and red
❖ Three-aspect - green, yellow, and red
❖ Four-aspect - green, yellow (twice), and red

81
 SIGNALLING – CLASSIFICATION – BASED ON FUNCTIONAL
CHARACTERISTICS
COLOUR LIGHT SIGNAL
Colour of signal Interpretation
Red Stop dead, danger ahead
Pass the signal cautiously and be prepared to stop at the next
Yellow
signal
Pass the signal at full speed but be prepared to pass the next
displayed together signal, which is likely to be yellow, at a
Two yellow lights
cautious speed Pass the signal at full speed, next signal is also
off

Green
Pass the signal at full speed, next signal is also off
82
 SIGNALLING – CLASSIFICATION – BASED ON LOCATION
CHARACTERISTICS
RECEPTION SIGNAL
➢ The signals which control the reception of trains into a station are called reception signals
➢ Two types - outer signals and home signals
➢ At some stations they also include routing signals
➢ OUTER SIGNAL
➢ First stop signal at a station, which indicates the entry of a train from a block section into the station
limits
➢ Provided at an adequate distance beyond the station limits so that the line is not obstructed once the
permission to approach has been given
➢ Provided at a distance of about 580 m from the home signal
➢ The signal has one arm but has a warner signal nearly 2 m below on the same post 83
 SIGNALLING – CLASSIFICATION – BASED ON LOCATION
CHARACTERISTICS
RECEPTION SIGNAL
➢ HOME SIGNAL
➢ After the outer signal, the next stop signal towards the station side is a home signal
➢ Provided right at the entrance of the station for the protection of the station limits
➢ The signal is located not more than 190 m from the start of points and crossings
➢ The arms provided on a home signal are generally as many as the number of reception lines in
the station yard
➢ When a home signal is in the ‘on’ (or stop) position it indicates that the train must come to a halt
short of the signal
➢ In the 'off' (or proceed) position, it indicates that the particular line is free and the train is
84
permitted to enter cautiously
 SIGNALLING – CLASSIFICATION – BASED ON LOCATION
CHARACTERISTICS
DEPARTURE SIGNAL
➢ The signals which control the departure of trains from the stations are known a s departure signals
➢ Two types: starter signal and advanced starter signals
➢ STARTER SIGNAL
➢ The starter signal is a stop signal and marks the limit up to which a particular line can be
occupied without infringing on other lines
➢ A separate starter signal is provided for each line
➢ The starter signal controls the movement of the train when it departs from the station
➢ The train leaves the station only when the starter signal is in the 'off' (or proceed) position
➢ As this signal controls the departure of a train, it comes under the category of departure signals 85
 SIGNALLING – CLASSIFICATION – BASED ON LOCATION
CHARACTERISTICS

ADVANCE STARTER SIGNAL

➢ This is the last stop signal provided for the departure of trains from a station
➢ The signal is provided about 180 m beyond the outermost points or switches and marks the end
of the station limits
➢ A block section lies between the advanced starter signal of one station and the outer signal of
the next station
➢ No train can leave the station limits until and unless the advance starter is lowered

86
87
 SIGNALLING – CLASSIFICATION – BASED ON SPECIAL CHARACTERISTICS
REPEATER OR CO ACTING SIGNAL
➢ In case a signal is not visible to the driver due to the presence of
some obstruction such as an over bridge, a high structure or due to
sharp curvature, another signal is used in its place, preferably on
the same post
➢ The signal, known as co-acting signal, is an exact replica of original
signal and works in unison with it
➢ A repeater signal is provided with an R marker can be of following
types
➢ A square – ended semaphore arm with a yellow background
and a black vertical band
➢ A coloured light repeater signal
88
➢ A rotary disc banner type signal
 SIGNALLING – CLASSIFICATION – BASED ON SPECIAL CHARACTERISTICS

ROUTING SIGNAL
➢ The various signals fixed on the same vertical post for both
main and branch lines are known as routing signals
➢ Signals indicate the route that has been marked for the
reception of the train
➢ Generally the signal for the main line is kept at a higher level
than that for the loop line
➢ It is necessary for the driver of a train approaching a
reception signal to know the line on which his or her train is
likely to be received so that he or she can regulate the
speed of the train accordingly
89
 SIGNALLING – CLASSIFICATION – BASED ON SPECIAL CHARACTERISTICS

CALLING ON SIGNAL
➢ This consists of a small arm fixed on a home signal post below the
main semaphore arm
➢ When the main home signal is in the horizontal (on) position and
the calling-on signal is in on inclined (off) position, it indicates that
the train is permitted to proceed cautiously on the line till it comes
across the next stop signal
➢ Calling-on signal is meant to 'call' the train, which is waiting beyond
the home signal

90
 SIGNALLING - INTERLOCKING
➢ Interlocking is a device or a system meant to ensure the safety of trains
➢ With the increase in the number of points and the signals and introduction of high speeds, it
has become necessary to eliminate human error, which would otherwise lead to massive losses
of life and property
➢ The points and signals are set in such a way that the cabin man cannot lower the signal for the
reception of a train unless the corresponding points have been set and locked
➢ The signal is thus interlocked with the points in a way that no conflicting movement is possible
and the safety of trains is ensured
➢ Interlocking can, therefore, be defined as an arrangement of signals, points, and other
apparatus so interconnected by means of mechanical or electrical locking that they can be
operated in a predetermined sequence to ensure that there is no conflicting movement of
signals and points and trains run safely
91
 INTERLOCKING - ESSENTIALS
• It should not be possible to turn off any two signals at the same time that can lead to
collision of train

• It should not be possible to turn off a signal unless all the points relating to line are set
and locked

• After the signal has been lowered (turned off) it should not be possible to make
adjustments in the points or locks on the route

• It should not be possible to lower the warner signals and outer signals unless
corresponding home signal is lowered

92
 METHODS OF INTERLOCKING

1. Key system
2. Tappets and lock system (Mechanical system)
3. Route relay system (Electrical interlocking)

93
 KEY SYSTEM
• Simplest method
• Manual method
• Used in small stations in India
• System may be of single key or double key system
• Single key system – Two locks are worked with a single key
• Double key system
• The point has two keys, one is for main line and other is for branch line
• Lever frame operating the signal has two levers and can be operated only by the
respective keys
94
 TAPPETS AND LOCK SYSTEM
• Mechanical interlocking method
• Less manpower is only required
• Greater safety
• Consists of locking frame, point fittings, signal fittings and connecting devices
• Connecting devices connects the locking frame to the point and signal fittings
• On each lever, a plunger is attached. The plunger has suitably shaped notches to
accommodate locking tappets
• The entire arrangement is provided in a locking trough where tappets are provided,
which moves right angle to the plungers
95
 TAPPETS AND LOCK SYSTEM
• When lever is pulled, connected plunger also
moves so that tappet is pushed out of the
notch and motion is transmitted to all other
tappets since all the tappets are connected
by a stretcher bar
• As a result of this motion, the other tappets
either get pushed into or out of the
respective notches of the other plunger
depending upon the type of interlocking
provided 96
 ROUTE RELAY SYSTEM
• The points and signals are electrically operated in this system
• Electrical interlocking is achieved through electric switches known as relays
• Most sophisticated system
• Saves man power and maintenance cost
• The entire track circuit and signal aspects are repeated on a panel by operating switches
• Relays use the simple principle of electromagnetism
• When the track is occupied by train, the lights on panel turn red
• When the train leaves the section the light goes off

97
 SYSTEMS FOR CONTROLLING TRAIN MOVEMENT
Absolute block system (Space interval or Lock Block System)
▪ Most extensively used in Indian Railways
▪Entire track is divided into block sections
▪ Stations are provided with block instruments in pairs
▪ Instrument is used to know whether the section ahead is clear or occupied.
▪ No train can leave station without receiving permission from next station in advance.
▪ No train is permitted to approach unless the receiving line is clear for an adequate
distance for a double track and no train in opposite or same direction in the case of single
track.
98
 SYSTEMS FOR CONTROLLING TRAIN MOVEMENT
Absolute block system (Space interval or Lock Block System) - Working

99
 SYSTEMS FOR CONTROLLING TRAIN MOVEMENT
Centralised traffic control system
(1)This is a progressive technique in control of points and signals from the non-interlocked to the
multiple cabin to the single cabin, then to remote control points and finally to centralized control of
points and signals over an entire section
(2) This is the latest system developed to control the movement of trains in which the points and
signals are operated from a central control room and no signal cabins are required
(3) In this system, the centralized traffic control panel is used which consists of illuminated track
diagram, showing the relative position of signals, points and track circuits together with their
reference numbers
(4)There are a number of thumb switches below the illuminated track diagram for the control of
points
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 SYSTEMS FOR CONTROLLING TRAIN MOVEMENT
Centralised traffic control system
(5) In addition, immediately below the point-thumb switches, the signal thumb-switches are
mounted to operate the signals in different positions
(6) There is also a switch to determine the directions of movement of trains. The signal in the
opposing direction remain in danger position.
(7) The person controlling the panel is known as Dispatcher. The Dispatcher makes all the
arrangements for crossings, points and signals
(8) The duty of drivers is merely to respect the different indications given by the signals
(9) The arrangements are also made in this system to display stop signals automatically in advance
and bring the trains automatically to a rest to avoid a collision, in case the driver does not obey
signal indications
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https://youtu.be/MpCsAQuWaH8 1
 SYSTEMS FOR CONTROLLING TRAIN MOVEMENT
Centralised traffic control system - Advantages
(1) This system increases the track capacity, so encourages to run additional trains. This is a
special benefit in cases of single line operation.
(2) As the signal cabins are not required, there is great saving in staff
(3) The Dispatcher, controlling the panel, can arrange the train movements in advance and is free
to do other works of the office.
(4) Points and signals can be operated in few seconds by means of thumb switches.
(5) This system is capable of detecting the defects of the track.
(6) The train can be run at maximum speeds as the driver has not to give signals, because the
driver is warned by means of whistle or red-light in his cabin if approaching to a stop-signal. Even
if he fails to obey the signal indications, the brakes will automatically applied to stop the train.
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2
 SYSTEMS FOR CONTROLLING TRAIN MOVEMENT
Automatic Train control system
➢ This system is practiced in America, Japan and Switzerland, and has recently been
approved to be introduced on some of the Indian Railways
➢ In India – Japanese system, of automatic train stop device ‘S’ type and Swiss system of
integral type shall be tried on these sections
➢ In these systems not only the tracks are electrical circuited, but there are electrical
fittings at the wheel brakes of the locomotives
➢ The advantage of these fittings is realized when the driver fails to obey the signal at
danger-position

10
3
 SYSTEMS FOR CONTROLLING TRAIN MOVEMENT
Automatic Train control system
➢ It works in different ways
➢ In Japanese system, red light continues to lit and bell keeps ringing in the driver’s cabin for 5
seconds to warn the driver
➢ In Swiss system, a siren continue to blow for 2 to 3 seconds. If still driver fails to respond, the
brake applies automatically and bring the train to stop
➢ If the signal is clear, the brakes will not apply automatically
➢ ATC consists of two parts
➢ Mechanical or electric installation to apply the brakes automatically
➢ Warning system installed in driver’s cabin 10
4
TRACK CIRCUITING

10
5
 TRACK CIRCUITING
➢ Track circuit is an electrical circuit formed along with running rails and connected to
signal, cabin, block instruments etc., for the desired indication by lights or bell or siren
etc.
➢ Thus track circuit function to indicate the presence of a train on the track whether the
track is occupied or clear
➢ For obtaining a track circuit, the ends of rails forming the circuit are isolated by using
insulated rail joints
➢ The ends of the rails on one side are connected to the two terminals of battery while
the other side is connected to an electromagnet called a ‘relay’ which is in energised
condition when there is no vehicle on the track – Primary circuit
➢ Presence of train or vehicle, short circuits the relay which gets de-energised breaking
the secondary circuit connected with signals and ensures the necessary signals should
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go to danger indication 6
 RAILWAY STATIONS
DEFINITION
• A Railway station is the selected place on a railway line, where trains halt for one or more of the following
purposes:
1. For exchange of passengers.
2. For exchange of goods.
3. For control of train movements.
4. To enable the trains on a single line track to cross from opposite directions.
5. To enable the following express trains to overtake
6. For taking diesel or coal and water for locomotives.
7. For detaching engines and running staff.
8. For detaching or attaching of compartments and wagons.
9. For sorting of bogies to form new trains, housing of locomotive in loco-sheds etc. 10
8
10. In emergencies in case of dislocation of track due to rains or accidents etc.
 Classification of stations

Operational Functional
Classification Classification

Special Non-block Wayside

Junctions
stations stations junctions

Block Terminal
stations 10
9
OPERATIONAL CLASSIFICATION
• BLOCK STATIONS
One • Class A, Class B & Class C stations.

• NON-BLOCK STATIONS
Two • Class D & Flag stations.

• SPECIAL CLASS STATIONS

Three
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 1. BLOCK STATIONS

• These are sort of compartments into which the railway line is divided (5 to 10 km), are
established so as to safety space the trains behind each other

• The ‘Block Stations’ are made at the ends of block section and are equipped with
signals which demarcate the limits of the block sections.

• A Block Station is a place on the railway line at which “permission to approach” &
“authority to proceed” are granted.

11
1
 1.1 ‘A’ CLASS STATIONS
• “A Class” is a station where the line has to be cleared up to an adequate distance
(400m) beyond the home signal for giving permission to approach to a train.
• Its minimum signal requirements are warner signal, home signal (first stop signal)
and starter signal

11
2
 1.2 ‘B’ CLASS STATIONS
• A “B Class” station is one, where the line has to be cleared up to an adequate
distance beyond the outer signal before giving permission to approach a train.
• Its minimum signal requirements are outer signal (first stop signal), home signal
and starter signal

11
3
 1.3 ‘C’ CLASS STATIONS
• A “C Class” Station is only ‘block hut’ where no passengers are booked. It is used as a
means to split a long block section so that the interval between successive trains is
reduced.
• Trains usually do not stop at this station
• Its minimum signal requirements are home signal (first stop signal) and warner
signal

11
4
 2. NON-BLOCK STATIONS
• Also called “D Class” or flag stations.

• Situated between two block stations.

• They do not define the boundary of any block section.

• They are neither telegraphically connected to adjacent stations nor have any apparatus or
staff for controlling the movement of trains.

3. SPECIAL CLASS STATIONS

• Special class stations are those which are not covered under ‘A’, ‘B’, ‘C’, and ‘D’ classes. 11
5
 FUNCTIONAL CLASSIFICATION

• Non-Junction or Wayside Stations

One

• Junction Stations
Two

• Terminal Stations
Three 11
6
 1. NON-JUNCTION/WAYSIDE STATIONS
• Consists of an arrangement for crossing an up and a down train or for overtaking the
slower trains by the fast moving trains. Eg: Kozhikode

11
7
 1.1 STATION ON A SINGLE LINE.
• Simplest layout of a wayside station.
• Consists of
i. A through line;
ii. A loop line to enable crossing;
iii. Passenger platform & Station building;
iv. A goods loop & a goods platform.

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8
 1.2 STATION ON DOUBLE LINE
• One or two passenger-platforms
• Island Platform: Platform, which is completely surrounded by the tracks
• Over-bridges or subways may be provided to facilitate the movement of passengers
• A cross-over is provided to facilitate movement of trains from one line to another
• A refuge line is provided to allow fast moving trains to overtake slow moving trains in
same direction
• Goods platform, goods shed, station building, and shunting track are also provided

11
9
12
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 1.3 STATION ON TRIPLE LINE
• Main line and two loop lines are provided on either side

12
1
 2. JUNCTION STATIONS
A junction station is one where a branch line joins a main line.

i. To facilitate the interchange of traffic.

ii. To release the engine for servicing.

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2
 3. TERMINAL STATIONS
• The station at which a railway line or branch terminates.
• Servicing of engines & vehicles are provided.
• In circulating area, all the facilities like ticket office, waiting hall for passengers
etc. are provided
• Directly connected to approach roads
• Ex: Howrah, Bombay etc.

12
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12
4
 UNIVERSITY QUESTIONS
1. What are the different types of signals according to location? Illustrate with the help of neat sketch (5)

2. Explain different types of railway signals according to their function. With the help of neat sketch explain the

essential features and working principle of a Semaphore type signal. (10)

3. Write short notes on warner signal, Shunting signal, and routing signal with neat sketches (6)

4. Explain with neat sketch Reception signal and Departure signals (5)

5. List out the different types of functional signals. Discuss in detail the working of any one signal with neat sketch.

(7)

6. Draw a sketch showing positions of various signals for a junction of two main line and two branch lines with a

siding (5) 12
5
 UNIVERSITY QUESTIONS
7. What is a yard? What are the different types of yards? Explain the functions of a Marshalling yard

and describe the points to be considered in its design. (10)

8. Explain locomotive yard and its components (5)

9. What is the purpose of providing marshalling yards? What are the main siding features of

marshalling yards? Support your answers with appropriate figures. (8)

10. What are the different systems of controlling the movement of trains? Explain the working of

absolute block system. (6)

11. What are the different systems of controlling the movement of trains? Explain the working of one
12
6
system which has been widely used on Indian Railways. (7)
 UNIVERSITY QUESTIONS
12. Differentiate between C.T.C. system and A.T.C. system (5)

13. How are railway stations classified? Explain each with neat sketches (10)

14. On a straight B.G. track, a turnout takes off at an angle of 6042’35’’. Design the turnout if angle of
switch is equal to 108’00’’, length of switch rails is 4.73 m, heel divergence is equal to 11.43 cm
and straight arm is equal to 0.85 m. (7)
15.Explain (i) Three-throw (ii) Gathering lines
16.Draw a neat sketch of a Right hand turnout and mark its component
17.A turnout is to be laid off a straight BG track with a 1 in 12 crossing. Determine the lead and radius
of turnout with the help of following data: heel divergence = 133mm, crossing angle 4˚45’49”,
switch angle 1˚8’0”, straight length between the theoretical nose of crossing and tangent point of
crossing = 1.418m. 12
7