Chapter 3 station,yards,points and crossing,signalling and interlocking

Dhara Dattani Lecturer @ AITSDS_Civil Dept
1
CHAPTER-3
STATION YARDS, POINTS & CROSSING,
SIGNALLING & INTER-LOCKING

FUNCTION OF RAILWAY STATION:
 A railway station is a place on a railway line, where trains
stop for clearing passengers and good traffic.
 Purposes / Function of railway stations
 1. For exchange of passengers
 2. For exchange of goods
 3. For control of train movements
 4. To enable the following express trains to overtake.
 5. To enable the trains on a single line track to cross from
opposite directions
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Purposes / Function of railway stations
6. For exchange of passengers
7. For exchange of goods
8. For control of train movements
9. To enable the following express trains to overtake.
10. To enable the trains on a single line track to cross
from opposite directions
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SELECTION OF SITE FOR RAILWAY
STATION:
 1. Adequate land
 2. Level area with good drainage
 3. Proximity to town or village
 4. Approach roads
 5. Alignment
 6. Water supply arrangement
 7. Station amenities
 8. Type of station and yard
 9. Role of authoritiesDhara Dattani Lecturer @ AITSDS_Civil Dept
5

REQUIREMENTS OF RAILWAY STATION:
 The requirements of a railway stations can be divided into
four groups:
 1. Public requirements
 2. Traffic requirements
 3. Engine requirements
 4. General requirements
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1. Public requirements:
 (i) Booking office
 (ii) Platforms
 (iii) Suitable lights
 (iv) Drinking water
 (v) Waiting rooms
and retiring room
 (vi) Sanitary
arrangements,
bathrooms
 (vii) Inquiry office,
Public telephone,
refreshment
 (viii) Name board
of the station and
platforms
 (ix) Microphones
to announce the
arrival and
departure of
trains.
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2. Traffic requirements:
 (i) Adequate traffic staff and
police staff
 (ii) Proper arrangements
such as staff rooms, retiring
rooms, and quarters etc. for
staff e.g. station master,
engine drivers, ticket
collectors, etc.
 (iii) Signals and signal cabins
for controlling the
movement of trains.
 (iv) Sufficient number of
siding to enable the trains to
cross or overtake each other.
 (v) Suitable platforms for
loading, unloading of goods
and passengers.
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3. Engine Requirements:
 (i) Proper arrangements for supply of fuel and water to
locomotives
 (ii) Arrangements for cleaning, examining, inspecting the
locomotives.
 (iii) Turn table to change the direction of locomotives.
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4. General requirements:
 (i) Easy and comfortable approach roads to stations
 (ii) Availability of coolies on the platforms at stations.
 (iii) Guide map of city, Installation of clocks for correct time
 (iv) Big waiting halls, benches for sitting
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TYPES OF RAILWAY STATION:
 Railway stations can be broadly classified into two groups:
a. Operational Classification
b. Functional Classification
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(a) Operational Classification
 RAILWAY STATION
BLOCK-STATION NON-BLOCK-STATION
A-CLASS B-CLASS C-CLASS D-CLASS FLAG STATION
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OPERATIONAL STATION
 BLOCK STATION: THE STATION WHICH ARE EQUIPPED BY SIGNALS &
DEMACRATION(BOUNDARY) TO PROVIDE SAFTEY FOR TRAINS COMING AFTER
ONE ANOTHER
 PERMISSION TO APPROCH AND AUTHORITY TO PROCEEED ARE GRANTED
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Signal
 Warner signal: Placed at warning distance from the Home
signal to indicate the section beyond is clear or not
 Home Signal: Which is first stop signal
 Starter Signal: It marks the line up to which the line should
be clear, for giving permission to approach
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400MT

‘B’ class station:
 This is the most common type of station and is provided on
signal line as well as double-line sections.
 It is one where the line has to be cleared up to an adequate
distance
beyond the outer signal before giving permission to approach
to a train.
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The minimum signals required at a ‘B’ class
station are:
 (i) Outer signal: An outer signal is the first stop signal. The
outer signal can also be below the warner signal.
 (ii) Home signal: It is placed at an adequate distance from
the outer signal.
 It is the practice to place the outer signal at a single line
station at an distance of 580 m from the home signal.
 (iii)Starter signal: A starter signal is also provided on a
double line section.
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‘C’ class station:
 The ‘C’ class station is only a block but where no booking of passengers is done.
 It is practically provided to split a long block section so that the interval between
successive trains is reduced. No train normally stops at these stations.
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The minimum signal requirements are as
follows:
(i) Warner signal: A warner signal is placed at an adequate warning distance from the
home signal to indicate whether the section ahead is clear or not.
(ii) Home signal: It is the first stop signal.
 The advantages of ‘C’ class station is that it ensures the faster movement of trains
and increase the line capacity.
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23

C Class station
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2) Functional consideration
 ( a) Halt station
 (b) Flag stations
 (c ) Road side or crossing stations.
 ( d ) Junction station.
 ( e ) Terminal stations
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HALT STATION
 A halt is the simplest station where trains can stop on a railway line.
 A halt has only a ail level platform, about 250 m long, with a name board at
either end of the platform.
 Sometimes a small waiting shed is also provided, which also serve as a booking
office.
 There is no station building or no yard provided for such type of stations.
 The selected trains stop at such stations to enable passengers to entrain or
detrain. The booking of passengers is done by travelling ticket examiners.
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Layout of Halt station
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FLAG STATION
 A flag station is provided with a station building and staff.
 It is also provided with a small waiting room and booking
office, benches and platforms, etc.
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Way side
 In this type of stations, the arrangement is made to cross an up and a down train or
for overtaking of the slower trains by the faster trains.
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 The important features of this track layout are:
 It is a three line station and provides facilities for the simultaneous reception of
trains from both sides.
 There is a dead and siding at either end of the station to accommodate wagons
that are marked sick.
 The foot over bridge is provided to help the passengers to reach the island
platform from the station building and vice versa.
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4. Junction stations:
 A junction station is one where a branch line joins a main line. At junction stations
 following arrangements are made:
 i. To facilitate the interchange of traffic between main and branch lines.
 ii. To clean and repair the vehicles of the trains which terminate at the junctions
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 Important features of junction stations are:
 There are two platforms-one is the main line platform and the other is an island
platform.
 A small goods siding and a goods platform is also provided to deal with goods
traffic.
 A foot over bridge is provided for passengers to move between the station
platform and the island platform.
 A turn table is also provided to change the direction of an engine.
 The emergency cross-over provided on either side of the station helps in switching
to a single line set up in the case of emergency.
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5. Terminal stations:
 In this station lines from 3 or more directions meet.
 Helpful for passengers to change line from one to
another.
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STATION YARDS

TYPES OF YARDS:
 A yard is a system of tracks laid usually on a level within
defined limits, for receiving, storing, making up trains,
dispatch of vehicles and for other purposes over which
movements are not authorized by a time table.
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1. Passenger Yard:
 The passenger platform is a passenger yard. The main
function of passenger yard is to provide facilities for the safe
movement of passengers and vehicles for the passengers.
 At large stations there may be many platforms but at small
station there is one platform near main line and there is one
loop line.
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2. Goods Yard:
 Functions of goods yard:
 (i) Receiving goods to be dispatched
 (ii) Loading and unloading of goods.
 (iii) Storing and delivery of goods.
 (iv) Connect and disconnect trains by shunting(PULLPUSH
THE TRAIN).
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 Requirements of goods yard:
 (i) Platform should be protected from rain and sun.
 (ii) Sufficient number of goods sidings.
 (iii) Good approach roads to goods yard.
 (iv) Godowns for storage of goods.
 (v) Loading gauges.
 (vi) Buffer stops
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3. Marshalling Yard:
 A Marshalling yard is a yard where trains and other loads are
received, sorted out and new trains formed, and dispatched
onwards.
 The marshalling yards are provided at all important junction
stations which act as distributing center for various
destinations.
 Thus, marshalling yards are the heart that pumps the flow of
commerce along the tracks. Marshalling yards are provided
at about 150 to 200 km distance.
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 The main components of the marshalling yard are:
 1. Reception sidings
 2. Sorting sidings
 3. Departure sidings
 4. Breakdown sidings
 5. Turn table
 6. Ash pit
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Reception sidings
52

Crossing sidings
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Departure sidings
54

Turn table
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 Main functions of marshalling yard:
 1. Reception
 2. Sorting
 3. Departure
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 Types of marshalling yard:
 1. Flat marshalling yard
 2. Gravitational marshalling yard
 3. Hump yard
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1. Flat marshalling yard:
 Entire space of the yard is almost level
 Sorting works of wagons are carried out by means of
engineers running to and fro.
 Arrangements is costly due to more consumption of power
in use of engines,
 Used where space is limited
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59 1. Flat marshalling yard:

2. Gravitational marshalling yard:
 In this type of yard, the tracks are laid at such a gradient, that
wagons can move of their own under the action of gravity.
Movements of wagons are controlled by wagon brakes
manually.
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61 2. Gravitational marshalling yard:

 Advantages:
 Less consumption of engine power
 Sorting of wagons is quicker.
62

3. Hump yard:
 In this type of yard humps or summits or artificial hills are
provided and wagons are pushed upon a hump by the
engine.
 This hump is located at the entrance of the sidings.
 Shunting operations are carried out more quickly than
gravity of flat yards.
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64 3. Hump yard:

65 3. Hump yard:

LOCOMOTIVE YARD
 These are the yards where facilities like cleaning, repairing,
servicing, watering, oiling, etc. are provided for the locomotives.
 (i) Inspection pit
 (ii) Ash pit
 (iii) Drop pit
 (iv) Turn table
 (v) Water column
 (vi) Small workshop
 (vii) First aid treatment
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 Types of loco yards:
 1. Circular yard
 2. Rectangular yard
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POINTS AND CROSSINGS
68

 Points and crossings are special arrangements provided on
railway tracks for enabling trains to be diverted from one
track to another.
 Functions of points and crossings:
 1. Points and crossings provided flexibility of movement by connecting one line to
another according to requirements.
 2. They also help to inposing restrictions over turnouts which necessarily retard the
movements.
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 A switch consists of a stock rail and a tongue rail.
 A set of switches consists of a left hand switch and a right
hand switch.
 Switches are tapered in shape with the thicker and known as
the heel fixed to the main track and thinner end known as
the toe movable by means of which the flanged wheels of the
the train are diverted from one route to another.
 When tongue rail moves away from the main rail, there will be
gap between tongue rail and main rail and the train goes
straight on the main line
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Components of switch:
 1. A pair of stock rails
 2. A pair of tongue rails
 3. Heel block or distance block
 4. Stretcher bar
 5. Switch tie plate
 6. Slide chair
 7. Studs or stops
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A pair of stock rail
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A PAIR OF TONGUE RAIL
74

HEEL BLOCK
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STRETCHER BAR
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POINTS OF SWITCH
77

POINTS OF SWITCH
78

SLIDE CHAIR
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CROSSINGS:
 A crossing or a frog is a device which provides two flange ways through which
the wheels of the flanges may move, when two rails intersect each other at an
angle.
81

Components of crossings:
 1. A CROSSING OR VEE PIECE
 2. Point and splice rails
 3. Wing rails
 4. Check rails
 5. Chairs at crossing, at toe and at heel
 6. Blocks at throat, at nose and at heel
82

Characteristics of good crossings:
 1. The assembly of a crossing has to be rigid to stand against serve vibration. For
this, for connecting the point and splice rails, sole plate and turned bolts should
be used.
 2. To prevent wear on parts of the wing rails, special steel should be used.
 3. The foot flanges of the wing rails should be connected to the sole plate using
rivets.
 4. The crossing body should be as long as possible.
 5. The thickness of crossing nose should be about 6 to 18 mm.
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TYPES OF CROSSING
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OBTUSE ANGLE
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SQUARE CROSSING
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SQUARE CROSSING
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SPRING CROSSING
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CROSS OVER CROSSING
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DIAMOND CROSSING
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GATHERING LINE
98

TURNOUT:
 Turnout is the simplest combination of points and crossings
by operation of which a train is diverted to another track.
 A turnout may be left hand turnout or right hand turn out
depending on whether the train from main track is diverted
to left or right.
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LEFT HAND TURN OUT
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Various parts of turnout:
 1. A pair of points or switches (ABCD or EFPQ)
 2. A pair of stock rails
 3. Vee crossing- GHIJ
 4. Two check rails
 5. Four lead rails
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 6. Switches tie plate or gauge tie chair and crossing tie plate.
 7. Studs and stops
 8. Bearing plates, slide chairs, stretcher bar, etc.
 9. Rods, cranks. Liver – for operating the points
 10. Locking box, lock bar, plunger bar for locking system.
102

LEFT HAND AND RIGHT HAND
TURNOUT:
 Left hand turnout:
 If a train from main track is diverted to the left of the main route in the facing
direction,
 then the diversion is known as left hand turnout.
103

 Right hand turnout:If a train from main track is diverted to the right of the main
route in the facing direction, then the diversion is known as right hand turnout.
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SIGNALLING AND INTERLOCKING
105

OBJECTIVES OF SIGNALING:
 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.
 It includes the use and working of signals, points, block instruments and other
equipment.
 Thus, signalling is a medium of communication between the station master or the
controller sitting in a remote place in the office and the driver of the train.
106

Objectives of signalling:
1. To provide facilities for the efficient movement of the
trains.
2. To maintain a safe distance between trains that are
running on the same line in the same direction.
3. To ensure safety of two or more trains that have to
cross or approach each other.
4. To provide facilities for the maximum utility of the
track.
5. To provide facilities for safe and efficient shunting
operations.
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6. To guide the trains to run at restricted speeds during
the maintenance and repair of track.
7. To safeguard the trains at converging junctions and
give directional indications at diverging junctions.
8. To ensure the safety of the train when it comes in
contact with road traffic at level crossing.
108

CLASSIFICATION OF SIGNALS:
 The railway signal can be classified into various categories on the basis of
following characteristics :
 1. Operational characteristics
 2. Functional characteristics
 3. Locational characteristics
 4. Special characteristics
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1. Operational characteristics:
 Based on the way of their operation, signals can be classified as:
 i. Audible signals
Detonators
 ii. Visual signals
 Hand signals
 Fixed signals
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2. Functional characteristics
 i. Stop signals
 ii. Shunt signals(indicates line is clear)
 iii. Speed indicators
 iv. Coloured light signals
111

3. Locational characteristics
 i. Outer signal
 ii. Home signal
 iii. Starter signal
 iv. Advanced starter signal
112

4. Special characteristics:
 i. Repeater or co-acting signals
 ii. Routing signals
 iii. Calling on signals
 iv. Point indicators
 v. Speed indicators
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CLASSIFICATION OF AUDIBLE & VISUAL
SIGNALS
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Audible signals:
 During foggy and cloudy weather when hand or fixed signals are not visible,
detonators are placed on the rails which explode with a loud sound when the
train passes over them.
 This sound draws attention of the drivers to the proximity of the signals
 Usually, the detonators are placed on the rails at least 400 to 500 m ahead of the
signal to enable the driver to stop the train or to obey the signal. The detonators
are fixed to the rails by means of clips.
116

Visible signals:
 1. Hand signals
 2. Fixed signals
117

1. Hand signals:
 Hand signals are given either by flags fixed to a wooden handle or by bare arms
during day time.
 In the night, hand lamps with movable green and red slides are used for
signalling purposes.
 The hand signals are generally used by guards, station master, cabin man, gang
man, key man, or point man.
118

Fixed signals:
 These are firmly fixed on the ground by the side of the track. They may be
further subdivided in to caution indicators or stop signals.
 i. Caution indicators
 ii. Stop indicators
119

Caution indicators:
 Caution indicators are provided to warn the driver that the track ahead is not fit
for running the train at normal speed. These signals are provided where
engineering works are underway.
120

Stop indicators:
 Stop indicators normally do not change their position. They inform the drivers
about the condition of the railway line lying ahead.
 The various types of stop signals used on Indian Railways are semaphore signals,
coloured light signals, etc.
121

Semaphore signals:
 The word semaphore was first used by a Greek historian. ‘sema’ means sign and
‘phor’ means to bear.
 The signal mechanism is so arranged that in normal position it indicates the stop
position.
 The functions of the various component parts of a semaphore signal are
described below.
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123

1. Movable arm:
 The arm of the semaphore signal on the side facing the driver is painted red with
a vertical white strip.
 The arm is 1.2 m to 1.7 m long, 23 cm to 25 cm wide at the inner edge and 25 to
35 cm wide at the outer edge. In the normal position, the arm remains
horizontal.
 The height of the center of the arm is kept 7.5 m above the ground.
124

2. Weight and lever arrangement:
 A lever capable of revolving about horizontal pin is provided. At one end, a
weight is
 attached and crank rod is attached to the lever through a cam. A wire is attached
to other
 end of the lever, which is taken to signal cabin after passing over pulleys.
125

3. Spectacle frame:
 The spectacle frame is consists of red glass at the top and green glass at the bottom with a
lighting arrangement for signalling at night. Sometimes yellow light glass is also provided
in the middle.
126

4. Crank or alternate mechanism:
 This is provided to ensure that the signal and crank move together. The crank is
fixed in the spindle where the movable are is fixed.
127

5. A crank rod:
 A crank rod is used to actuate the crank or other mechanism provided.
128

6. A ladder:
 As the height of the movable arm is about 7.5 m above the ground level, a
ladder is
 provided for physical connection between the movable arm and the ground
level.
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Working principle:
 Working principle:
 The ordinary position of signal is horizontal but it can be lowered to an angle by
pulling
 the wire from the signal cabin.
 When the signal is in horizontal position, it is said to be in ‘ON’ position, which
 indicates ‘STOP’ or ‘DANGER’.
 When the signal is lowered by pulling the wire at an angle of 45o to 60o, it is said
to
 be in ‘OFF’ position, which indicates ‘PRODEED’.
 The indication given by semaphore signals are given in table
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132

STOP SIGNAL
• The normal position of the signal is horizontal
& it can be lowered at an angle of 45o to 60o
with horizontal by pulling the wire from the
signal cabin. In the horizontal position, the
signal indicates the “danger stop” & it is said
“on position”. When the arm is in inclined
position it indicates “clear-proceed” & is said
in “off-position”.
• In the night, the light of the lamp passing
through the spectacles gives signals. Thus red
light indicates danger and green light
indicates clear.

STOP SIGNAL
The length and width of arm vary from
120-167 cm and 23-35 cm respectively
The outer end of the arm is about 2.45 cm
Broader than that of the hinged end
It is placed on the left hand side of the
direction of movement of train
The side of the arm facing the driver is
painted red with white band near the
end
The other side is painted white with
black bands
7.67 m

Operation Time Position Of Arm Position Of Signal Indication Given
Day Time
Horizontal Arm ON Stop
Inclined At 60o
or 45o OFF Proceed
Night Time
Red Light ON Stop
Green Light OFF Proceed
STOP SIGNAL

Warner signals:
 Signals placed ahead of the stop signals to warn the driver before entering the
station
 These signals are similar to stop signals with the exception
that at their free end V notch is cut to distinguish it from stop signals
 Warner signals are placed generally at about 540 m away from the stop signals
 SIGNAL INDICATIONS
 Inclined Position: Track is clear and driver can proceed with
confidence
 Horizontal Position: Deriver can take his train upto
Stop signal cautiously
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 Some times both warner and semaphore
 signals are placed on the same pole
 SIGNAL INDICATIONS
• Both in Horizontal Position: Neither approaching section nor next block is clear
• When Semaphore is inclined and Warner Horizontal proceed with precaution i.e.
section up to station is clear but not the block beyond.
• Both in Inclined Position: Track is clear and proceed with confidence
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140

Shunting Signals
 Also called as disc or ground signals or
miniature semaphore signals
 Used during shunting operations
 Consist of a circular disc painted white with a
red band along its diameter.
 Red band is horizontal – stop
 Red band is inclined – proceed
 Similar to semaphore these are also provided
with lamp and colored glasses

DISC SIGNAL
These are shunting signals which are used for low speed
movements during shunting operations. They consist of
circular discs with red bands on white background
SIGNAL INDICATIONS
When Red band is Horizontal: Stop
When Red band is Inclined: Proceed

COLORED LIGHT SIGNALS
These are automatic signals & give
indications by electric lights both during the
day as well as in night.
The signals are provided with green,
yellow and red light.
These signals are provided with special lenses
& hoods to emit beam of light which can be
visible from a long distance even during the
day.
Proceed
Proceed with
Caution
Sto
p

 In India, mostly three aspect or four aspect coloured light signalling is used. In the
case of three aspect signalling, green, yellow, and red lights are used.
 Green indicates ‘proceed’, yellow indicates ‘proceed with caution’ and red indicates
‘stop’.
144

REPEATING SIGNAL
When the view of the main signal is obstructed due to
some structures or on curves etc. some signals are used to
repeat the information of the main signal. Such signal are
know as repeating signal.

CALLING ON
SIGNAL
These signal are similar to semaphore signal, but they
are smaller in size and are fixed on the same post below the
main signals. A calling on signal permits a train to proceed
with caution after the train has been brought to a halt by
the main signal. These are helpful when repair works are
going on.

Inter locking
147

INTERLOCKING:
 Interlocking can be defined as an arrangement of signals,
points and other apparatus
 So inter connected 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.
148

 1. It shall not be possible to turn a signal ‘OFF’ unless all
points for the line on which the train is to be received are
correctly set, all the facing points are locked, and all
interlocked level crossings are closed and inaccessible to road
traffic.
 2. The line should be completely isolated before the signal is
turned off.
 3. After the signal has been turned off, it should not be
possible to make adjustments in the points or locks on the
route, including those in the isolated line.
149 Essential principles of interlocking:

 4. No interlocking gates should be released until the
signal is replaced in the ‘ON’ position.
 5. It should not be possible to turn any two signals off at
the same time, as this can lead to conflicting movements of
the train.
 6. Wherever possible, the points should be so interlocked as
to avoid any conflicting movement.
150

Methods of interlocking:
 Key inter locking
 Mechanical interlocking
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152

 Consider a station with a main line and a branch line. The point can be set either
for main line or branch line.
 The point has two keys. The first key A can be taken out when the point is set and
locked for the main line.
 Similarly, key B can be taken out when the point is set and locked for the loop line.
 At any given time either key A or key B can be taken out, depending upon whether
the route is set for the main line or the loop line.
153

 3. Two levers are provided on the lever frame. The lever concerning the main line
signal can be operated only by key A.
 Similarly the branch line signal lever can be operated only by key B.
 If the trains is to be received on the main line, the points are set and locked for the
main line and key A is released. This key is used for unlocking the main line signal
lever.
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 Improved form of interlocking compared to key
interlocking
 Greater safety and less manpower
 Main components are
 Locking frame
 Point frame
 Signal fittings
 And connecting devices
 Levers are arranged in a row in the frame
156

 Pulling a point lever operates the point to which it is connected through a steel rod.
 Pulling a signal lever changes the signal by pulling the wire connecting the lever
and signal
157

 Normal interlocking:
 Pulling one lever locks other lever in normal position
 Back locking or release locking:
 Lever in normal position locks the other lever in normal
 position.
 When pulled other lever released and is free to operate
 When other pulled, first one gets locked in pulled position.
 Both wall locking:
 Once the lever is locked other lever locked in current
position.
158

159

160

Panel interlocking
 All points and signals are operated electrically
 from a central location
 The switches for operating these points and signals are mounted on a panel,
which also bears the diagram of the yard layout
 Electrical interlocking is achieved by means of relays
 Centralized controlling of greater area is great
 advantage
161

Route Relay Interlocking
 Improvement over panel interlocking
 In panel interlocking each point in the line has to be individually setup with a
switch and clearance of signal is obtained by operating the switch.
 In R.R.I only a pair of switches are used for doing all these operations
automatically.
 Signal is also cleared in the similar automated
 manner
 The main requirement for this type of interlocking is entire track needs to be
track circuited.
162

 The conditions of track circuit and various indications of all signal are
mirrored on the panel that carries the diagram of the yard.
 By looking at these indications a panel operator can a panel operator can easily
know whether a track is free or not.
 Once the route is set to allow, the portion gets
 illuminated with white light.
 If the route is occupied, it will show in red colour.
 If the train has cleared the track, the lights will off.
163

END OF CHAPTER-3
164

Chapter 3 station,yards,points and crossing,signalling and interlocking

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Chapter 3 station,yards,points and crossing,signalling and interlocking