Indian Railway Signalling concepts and basics.pdf

CHAPTER -1
INTRODUCTION TO RAILWAY SIGNALLING
SUBJECT IRISET- SECUNDERABAD 2

Railway signalling
• Railway Signal- apparatus used to provide non-
verbal, safe and precise information to driver
• Aspect- How signal appears ( Red, Yellow& Green )
• Indication- Information provided by aspect
• ON aspect- Most restrictive aspect ( RED for Stop Sig)
• OFF aspect- Other than ON aspect ( Yellow / Double
Yellow/ Green )

ROAD SIGNAL Railway signal

Two Aspect Lower Quadrant Signalling
ON Aspect: 00 to 50
Indication- Stop Dead
OFF Aspect: 450 to 600
Indication- Proceed
7
02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0
I. Stop Signal

Stop Dead Proceed and be prepared to
stop at the next Stop Signal
Proceed
400 to 450 850 to 900
8
00 to 50
Upper Quadrant Semaphore Signalling
I. Stop Signal

Multiple Aspect Colour Light Signals
I. Stop Signal (Three aspect)
9
Proceed
Caution
Stop

10
Stop Signal (Four aspect)

Need for Signaling in Railways:
• Signalling in railways has evolved for the following:
• Running trains safely by securing it`s intended path.
• Handle more trains effectively.
• Unambiguous & Timely Communication to Loco
Pilot for regulating speed of train
• The Train Loco Pilot is very much dependent on the
aspect of the signal for controlling the speed of train

Railway Signalling conveys the following
• Timely information to Loco Pilot for regulating
speed of his train.
• Information is conveyed by a signal showing various
aspects.
. Many signals are interlinked for giving advance
information.
• A signal ensures
• Physical clearance of intended path.
• Securing various points in the path.
• Closure of Level crossing gates.
• No other train is moving in this path.

Point
G.V. Rao 15
Stock Rail, Tongue rail ( Switch rails )
STOCK RAIL

POINTS : A Mechanism provided on the track to facilitate
diversion of trains from one route to another.
(Our Engines do not have steering wheel as available in motor
cars)
Trailing Point
Facing Point
Facing Point & Trailing Point
Crossing

Point reverse
Sig yellow with route

Point normal
Sig yellow without route

Point.A Pt.B
X Y
Z
Pt.C
Pt. A for train X
Pt. B for train Y
Pt. C for train Z
Pt. B for train Z
T
F
F
T
EXAMPLE

25
TURNOUTS
FACING POINT
TRAILING POINT
SE4-CAVACH VER-1.0 IRISET- SECUNDERABAD

Station yard ( Points )
S.V. Rao 26

Signalling concepts
CONTROL OVER MOVEMENT OF TRAINS
Time Interval Method and
Space Interval Method
02.06.2020 27
S1 Basics of Indian Railway Signalling Ver.1.0

• Trains cannot be steered away as in the case of other
transports.
• They are required to follow one another in the same
direction on the length of track.
• Another set of diversion track is required to be provided
either for overtaking vehicles moving in the same direction
or for crossing the vehicles from the opposite direction.
Control over movement of trains
02.06.2020 28

Time Interval Method-
• Different types of trains like, Express/Mail, passenger,
high-speed freight and low speed freight shunting
trains are running etc.
• The speed of all the trains are not same
• The terrain of the country is not same everywhere
• The brake power, hauling capacity, load of train is not
same for all trains; and
• The stopping places of all trains are not the same
02.06.2020 29

Space Interval Method
• In this method of "Control over movement", the length
of track is divided into sections called "Blocks".
• The entry of a train into the ‘block’ is controlled in such
a way that only when it is free, a train can be allowed
to enter it.
• This means that between two consecutive trains, there
is a definite space interval.
02.06.2020 30

• The space interval system uses the block working wherein
the entry of train onto the block section is jointly
controlled by the entry and exist points of the block
section.
• The driver is authorized to proceed into a section by the
signal controlling the entry to the section.
• The main purpose of Railway Signalling Systems is to
maintain a safe distance between trains on the same track.
02.06.2020 31

Fixed Signals: GR 3.03 to 3.51
Hand Signals: GR 3.52 to 3.58
Detonating Signals:
GR 3.59 to 3.64
Flare Signals: GR 3.65 to 3.67
SIGNALS
32
T
N
A
R
D
U
A
Q
L
O
W
E
R
M
E
V
O
M
E
N
T
IN
N
I
T
N
E
M
M
O
V
E
T
A
N
U
A
D
R
Q
R
E
P
P
U
RH
UQ
LQ
RH
LH
LQ
UQ
LH

33
TYPES OF SIGNALS
Note: CLS - Colour Light Signal
Signals
Visual Audible
Voice Whistle
Detonators
Flare Signal Fixed Signal
Subsidiary
Running
Multiple Aspect
Colour Light Signal
Movable
Flag Signal
Shunt
Signal
Calling On
Signal

34
STOP:
PROCEED:
Hand Signals

Hand Signals
35
Move slowly for
coupling
Move towards the
person signalling

Flare Signals
36

Detonating Signals
37

Banner Flag
38
• A banner flag is a temporary fixed danger signal,
consisting of a red cloth supported at each end on a
post and stretched across the line to which it refers.

Block Instruments
02.06.2020 39

Block Instruments
02.06.2020 40

CHAPTER -2
INTRODUCTION TO RULES,
MANUALS AND SPECIFICATIONS

General and Subsidiary Rules (G&SR)
• The General Rules for Open Lines of the Railways
1976 have been framed under Section 198 of the
Railways Act 1989 by the Government of India.
• GR is common for all zonal Railways
• GR is issued by Railway Board
• The Subsidiary Rules ( SR ) and the Special
Instructions of the Zonal Railways are issued by the
Principle Chief Operations Manager, the Authorized
Officer, on the authority of GR 1.02 (5).

Signal Engineering Manual (IRSEM)
• Signal Engineering Manual deals with items of general
nature, organization of Signal and Telecommunication
department, duties and responsibilities of Officers
and staff at various levels and general requirements
for installation of signaling equipments etc
• IRSEM Issued by Railway Board

Telecom Manual
• This manual provides detailed guidelines for setting
up and maintaining the telecommunication
systems. This manual also gives an overview about
Organization of the Signal and Telecommunication
Department both at Headquarters and at Division.
• This manual is issued by Railway Board,

A.C Traction Manual
The "A. C. Traction Manual" contains installation,
maintenance and operation of 25 kV/AC 50 Hz
single phase traction installations, electric
locomotives and electrical multiple units and other
connected matters including railway electrification.
• This manual is issued by Railway Board.

Permanent way Manual
• The manual contains uniform procedures and
practices to be followed on Indian Railways by
Engineering department
Block Manual
• This manual contains instructions in detail
regarding block working pertaining to that railway
• This manual is issued by Principle Chief Operations
Manager ( PCOM )

Accident Manual
• This manual contains all the rules regarding the
class and description of accidents, accident
Enquiries and procedures for reporting accidents.
• This manual is issued by Principle Chief Operations
Manager
Schedule of Dimensions (SOD)
• The Schedule of Dimensions is meant to safeguard
the interests of both the rail users as well as the
railways and must be rigidly followed by the
railways

Indian Railway Standard Specifications
• Specifications for materials used for signalling
purposes have been drawn out by the Director
General, Research, Designs and Standards
Organisation (DG/RDSO), Ministry of Railways,
Lucknow and are titled as "Indian Railway Standard
Specifications

• Some of the specifications are listed below
• RDSO/SPN/ 153 /2011 for LED Signals
• IRS-S-63 /2007 PVC Signalling Cables
• IS-266 for ACID
• IS 1069 for Distilled water

• CCRS -CHIEF COMMISSIONER OF RAILWAY SAFETY, CRS
(under approved special instructions) means an
Inspector appointed to exercise any functions under
the Act, and includes a Commissioner of Railway Safety
• Authorized officer (special instructions) means
instructions issued from time to time by the
authorised officer in respect to particular cases or
special circumstances.

IRISET 51
MSDAC – Comparative Study Ver 1.0

CHAPTER -3
DEFINITIONS ( GR 1.02 )

Definitions
53
Adequate Distance:
– means the distance sufficient to ensure safety.
Signal 1 Signal 2
For taking off Signal 1, portion shown beyond Signal 2
must also be clear. This portion is the Adequate
Distance.

• INTERLOCKING- means an arrangement of signals,
points and other appliances, operated from a panel or
lever frame, so interconnected by mechanical locking
or electrical locking or both that their operation must
take place in proper sequence to ensure safety
• MULTIPLE ASPECT SIGNALLING- means a Signalling
arrangement in which signals display at any one time
any one of the three or more aspects and in which the
aspect of every signal is pre-warned by the aspect of
the previous signal or signals.

02.06.2020 55
Mechanical Interlocking

RELAY INTERLOCKING

RELAY INTERLOCKING
02.06.2020 57

ELECTRONIC INTERLOCKING

ASPECT & INDICATIONS OF MACLS
ASPECT STOP CAUTION PROCEED
INDICATION STOP DEAD Proceed & be
prepared to stop
at next signal
PROCEED

Block Section
Means that portion of the running line between two block
stations on to which no running train may enter until Line Clear
has been received from the block station at the other end of
the block station.
Block section = LSS ( Rear Stn ) to FSS ( Advance Stn ) +
Adequate distance
Station
1
Station
2
Block Section Home Signal
Adv. Starter
Block
Overlap
60

61
At a class B station provided with manually operated MA
signals, which is included-
(a) On a double line-
i) Between the outermost facing points and the last
Stop Signal of the station in either direction, or
ii) Between the BSLB where provided and the Last
Stop Signal of the station in either direction, or
(b) On a single line-
i) Between the Shunting Limit Boards or Adv. Strs (if
any), or
ii) Between the outermost facing points, if there are
no Shunting Limit Boards or Adv Strs.
Station section

Station Section (shown in green)
62

Station Limits- means the portion of a railway which is
under the control of a Station Master and is situated
between the outermost signals of the station or as may be
specified by special instructions.
Example:
The Station Limits are reckoned between the Distant and
the last stop signal in each direction on single distant
territory
63

Block Back:
– Means to dispatch a message from a Block Station
intimating to the block station immediately in rear
on a double line or to the next block station on
either side on a single line, that the block section is
obstructed or is to be obstructed.
Station 2 Blocks
Back this line
Station 1 Station 2
Station 1 blocks
back this line
64

Block Forward:
• Means to dispatch a message from a Block Station on a
double line intimating to the block station immediately
in advance the fact that the block section in advance is
obstructed or is to be obstructed.
Station 1 Block
Forward this line
Station 2 blocks
Forward this line
Station 1
Station 2
65
02.06.2020

In Rear of a Signal: means the territory over which an
approaching train has to pass before reaching the signal
location.
In Advance of a Signal: A term used in defining a
territory beyond a signal as seen from the approaching
train
In rear of signal In advance of signal
Direction of train
66

Line Capacity- means the maximum number of trains
that can be run on any given section during a calendar
day of 24 hours.
Running Train- means a train which has started under an
authority to proceed and has not completed its journey.
Day -means from sunrise to sunset.
Night- means from sunset to sunrise.
67

FOULING MARK -means
the mark at which
the infringement of
fixed Standard
Dimensions occurs,
where two lines cross
or join one another.
FM

Classification of Stations
Block Stations : Class A,
Class B,
Class C.
Non-block Stations: Class D
69

Approved Special Instructions- mean special
instructions approved of or prescribed by the
Commissioner of Railway Safety.
Authority to Proceed means - the authority given to
the driver of a running train under the system of
working to enter the Block Section with his train.
70

Fixed Signal
Definition: GR 1.01(22)
A signal of fixed location indicating a condition
affecting the movement of a train and includes fixed
light for use by day and fixed light for use by night.
MACLS – Multiple Aspect Colour light signalling
71

TRACK CIRCUIT -means an electrical circuit
provided to detect the presence of a vehicle on a
portion of track, the rails of the track forming part
of the circuit.

Track Circuit
Track relay
Battery
Track feed Battery
Charger
TL JB TL JB
RT
Glued joints Glued joints

IRISET 74

CHAPTER -4
FIXED SIGNALS , ASPECTS &
INDICATIONS

MACLS
Main
signals
Subsidiary
signals
Misc
signals
SE4-CAVACH VER-1.0 IRISET- SECUNDERABAD 76

Main
signals
Reception
signals
Distant
signals
Home
signal
Dispatch
signals
Starter &
LSS

• Same aspect by Day and Night.
• Luminous signals. Do not depend on reflected light
for visibility.
• Electrical operation hence fast response
• No mechanical transmission; no moving parts; no
drooping of signals; no restriction on range of
operation.
78
MACLS - Advantages

• Ahead signal aspects pre-warned by rear signals
• Long range of operation
• Better visibility of Main signals
• Maximum four aspects possible
• RG aspect at drivers eye level
• Less maintenance due to wear & tear less

80
Proceed
Caution
Stop

81
ASPECT & INDICATION OF MULTIPLE ASPECT COLOUR LIGHT SIGNAL
INDICATION STOP DEAD PROCEED & BE
PREPARED TO STOP AT
THE NEXT STOP SIGNAL
PROCEED
Stop Signal (Three aspect)

82

INDICATION STOP
DEAD
PROCEED & BE PREPARED TO
STOP AT THE NEXT STOP SIGNAL
PROCEED
ASPECT & INDICATION OF MACLS
SE4-CAVACH VER-1.0 83
IRISET- SECUNDERABAD

84

ASPECT STOP CAUTION ATTENTION PROCEED
INDICATION STOP DEAD PROCEED & BE PREPARED
TO STOP AT THE NEXT
STOP SIGNAL
Proceed &be prepared to
pass next stop signal at
restricted speed
PROCEED
ASPECT & INDICATION OF MULTIPLE FOUR ASPECT COLOUR LIGHT SIGNAL
SE4-CAVACH VER-1.0 85
IRISET- SECUNDERABAD

02.06.2020 S1 Basics of Indian Railway Signalling Ver.1.0 86
Yellow
P P P
Yellow
Yellow
Green
Distant Signal
ASPECT Caution Attention Proceed
INDICATION
Proceed & be
prepared to stop at
next Stop Signal
Proceed & be prepared to pass next
Stop Signal at such speed as
prescribed by special instruction
Proceed

Multiple Aspect Colour Light Permessive Signal
P P P

Symbols used to show Signals
88

IRISET 89

CHAPTER -5
DESIGNATION OF SIGNALS

Fixed Signals
Multiple Aspect Colour Light
Signals
91

Signals at Stations
Multiple Aspect Signals:
Reception Signals:
• Distant
• Inner distant
• Home ( FSS )
Dispatch Signals:
• Starter
• Intermediate Starter
• Advanced Starter ( LSS )
GR 3.07 (6) covers
the provision of 2
Distant Signals.
92

93
Proceed
Caution
Stop

94
I. Stop Signal (Four aspect)

II. Distant Signal
P P P
95

Calling On signals
96
‘C’ Marker Driver to obey
Calling On Signal

Position Light Type shunt signal
97
ON ASPECT OFF ASPECT

Advance Starter or SLB or BSLB
• At class B single line stations:
• AS or SLB required if obstructing of line outside Home is to be
permitted.
• Distance between AS or SLB and opposing FSS shall not be less
than 400m (for 2 aspect) or 180m (for MA)
• At class B double line stations:
• BSLB only for MA
• Only where there are no points or outermost points at
approaching end are trailing
• Located not less than 180m in advance of Home and protects
outermost trailing points, if any
99

100
BLOCK
SECTION
LIMIT BOARD
SHUNTING
LIMIT BOARD
Block Section Limit Board and Shunting Limit Board

IRISET 101

CHAPTER -6
SUBSIDIARY SIGNALS, INDICATORS &
MARKERS
102

Calling –ON Signal
103
Subsidiary Signals

Subsidiary signal ( Shunt sig )

Subsidiary Signals
105
• Signals which control movement of trains within the
Station Section are :-
– Shunt signals
– Calling-on Signals
And are called as Subsidiary Signals

Special features of Subsidiary signals
106
• These signals authorize movement at slow speeds
only.
• Movement is within the station area.
• Unlike running signals, they may authorize movement
on to occupied lines.
• Visibility of signals is not critical.
• Pre-warning is not required.

Shunt Signal (GR 3.14)
107
• Used for shunting within the station yard, Movement is
authorized at such slow speed as to be able to stop short of
any obstruction
• GR 5.13 (3) : The speed during shunting operations shall
not exceed 15 kmph unless otherwise authorized by special
instructions
• Can be on a post by itself or below a stop signal (except
the First Stop Signal)
• More than one shunt signal may be placed on the same
post
• When taken off, it authorizes the driver to draw ahead
even though the Stop signal above it may be On

Subsidiary signal ( Shunt Sig )

109
Shunt signal when taken 'OFF' authorises the driver to
draw ahead with caution even though the stop signal, if
any, above it is at 'ON' position,
 The shunt signal shall be
•Position Light Shunt Signals.
 When a Shunt Signal is placed below a Stop Signal, it shall
show no light in the "ON“ position.
SHUNT SIGNALS (GR 3.14)

Shunt below starter Independent shunt signal

Calling On signal
111
• Have no independent existence
• Provided below Stop Signal governing approach of
train expect Last Stop Signal
• C- Marker should be provided
• Train can be received on occupied line
• Train movement with in station section only

Calling On signal in CLS
112
‘C’ Marker
Driver to obey
Calling On
Signal

Calling –ON signal below starter signal

Indicators and Markers
114
 Indicators and Markers are provided on certain
signals or points to provide extra information
to the Drivers.

Indicators and Markers on MACLS
115

Markers on Colour Light Signal Posts
116
R
C
P
A
IB
A
Auto Signal
Semi
Auto Signal
Permissive
Signal
Intermediate
Block Signal
Calling-On
Signal Repeating
Signal

Markers on Colour Light Signal Posts
117
A G A AG
Gate Signal in
Auto Territory
Gate Signal in Semi Auto
Territory when interlocked
with Points also
G
Gate Signal
A A AG

Gate Stop Signal
118

119
Distant Signal

120
Calling- ON Signal

121
Automatic Signal

122
Semi Automatic Stop Signal
A

123
Gate stop Signal in Automatic Territory
A

124
Gate Stop Signal in Automatic Territory
A
A
A
AG

125
Points are correctly set,
locked LC gate is closed
properly and signal is
working as Automatic
Signal
A

126
LC gate is defective but
points are correctly set,
locked and signal is
working as Gate stop
Signal
AG

Point Indicator
127
They show a white
target (during day) or a
white light (during
night) in both
directions when points
are set for straight &
no target or green light
when set for turnout.
SET FOR
STRAIGHT
SET FOR
TURNOUT
TARGET TYPE POINT INDICATOR
 Point indicators are appliances fitted to points to
indicate the position in which the points are set.

128
Trap Indicators
 Trap indicators are
appliances fitted to
Trap points to
indicate the position
in which they are set.

Trap Indicators
129
TRAP OPEN
OR
DERAIL ON
TRAP CLOSED
OR
DERAIL OFF
TARGET TYPE TRAP INDICATOR
They show a red
target (during day) or
a red light (during
night) in both
directions when trap
points are open &
no target or green
light when trap points
are closed.

Route Indicators
130
 A common signal with route
indicator is provided in lieu of
separate signals on a bracketed
post or a gantry.
 A Route indicator may be of :
◦ Stencil type
◦ multi-lamp type
◦ junction type

DIRECTIONAL TYPE
ROUTE INDICATOR
MULTI LAMP TYPE
ROUTE INDICATOR
STENCIL TYPE
ROUTE INDICATOR
[For any speed ] [Speed up to 15 kmph]
[Speed up to 15 kmph]
Route Indicators

132
BLOCK
SECTION
LIMIT BOARD
SHUNTING
LIMIT BOARD
Block Section Limit Board and Shunting Limit Board

133
Goods warning Board
Passenger warning Board

134
T
P
10
10
S
Caution
Indicator
Termination
Indicator
Speed
Indicator
'S' Marker
Board
Various Indicators used by permanent way Department

135

136

137

IRISET 138

CHAPTER -7
OVERLAPS ( SIG &
BLOCK OVERLAPS)

Adequate distance
140
• GR 1.02 (2), Adequate Distance means the distance
sufficient to ensure safety.
• This is the length of track in advance of a signal
which must be kept clear before the signal next in
rear can be taken off.

Adequate distance (contd.)
141
Conditions for taking off Stop Signals -
 GR 3.40: The Home signal shall not be taken off unless,
 On a double line the line is clear for an adequate
distance beyond the starter, or
 On a single line, line is clear for an adequate distance
beyond the trailing points.
(except at a terminal station or unless the train has been
brought to a stop in rear of it)

 GR 3.42: The LSS or IBS shall not be taken OFF for a train
unless Line Clear has been obtained from the block station
in advance.
 GR 8.01 (1) (b) & (c ) : Such Line Clear shall not be given
unless the line is clear not only up to the FSS but also for an
adequate distance beyond it.
142

143
BLOCKSECTION
BLOCKOVERLAP
ACTUALROUTEOFLSSOFSTN'A'
STN'A'
RUNNINGLINE
STN'B'
LSSOFSTN'B'
LSSOF
STN'A'
FIRSTSTOP
SIGNALOFSTN'B'
PORTIONOFTRACKTOBEKEPTCLEARBEFORE
"LINECLEARISGIVENBYSTN'B'TOSTN'A'
P
DISTANT
SIGNAL

GR 9.01(c ) ( i ): The automatic signal shall not assume
off aspect unless the line is clear not only up to the next
Stop signal in advance but also for an adequate distance
beyond it
A Stop Signal shall not display Off aspect unless the line
is clear not only up to the next stop signal but also an
adequate distance beyond it.
Adequate distance (contd.)
144

OVERLAP
OVERLAP- means the length of track in advance of a stop
signal (S2), which must be kept clear, either for clearing
the stop signal next in rear (S1)or for the purpose of
granting permission to approach.
S1
Route of signal S1
S2
Overlap of S1

1.4 km
(a) SIGNAL OVERLAP IN 2-ASPECT
(b) SIGNAL OVERLAP IN M.A.S.
S.O = 120 mts
OBSTRUCTION
OBSTRUCTION
B.O = 180 mts
(d) BLOCK OVERLAP IN M.A.S.
(c) BLOCK OVERLAP IN 2-ASPECT
B.O = 400 mts
OBSTRUCTION
1 km
B
A
1 km
PASSENGER
WARNING BOARD
FIRST STOP
SIGNAL
DISTANT
SIGNAL
FIRST STOP
SIGNAL
GOODS WARNING
BOARD
P
1.4 km
(b) SIGNAL OVERLAP IN M.A.S.
S.O = 120 mts
OBSTRUCTION
B.O = 180 mts
(d) BLOCK OVERLAP IN M.A.S.
(c) BLOCK OVERLAP IN 2-ASPECT
B.O = 400 mts
OBSTRUCTION
1 km
1 km
PASSENGER
WARNING BOARD
FIRST STOP
SIGNAL
DISTANT
SIGNAL
FIRST STOP
SIGNAL
GOODS WARNING
BOARD
P

147
Type of signal
Signals MACLS Automatic signaling
on double line
Automatic
signaling
on single
line
Signal
overlap
120 Mtrs.
120 Mtrs. 120 Mtrs.
Block
overlap
180 Mtrs. --- -----
Overlaps

Sand hump
148

IRISET 149

150
CHAPTER -8 & 9
Braking Distance, Sighting Distance &
Visibility of Signals

Braking Distance
151
• The distance travelled by a train after its brakes are
applied is known as the Braking Distance.
• When normal or service brakes are applied (shutting
off power and gradual application of brakes), the distance
travelled is called Service Braking Distance (SBD).
• When emergent brakes are applied (shutting off power
and full application of brakes), the distance travelled is
called Emergency Braking Distance (EBD).

Braking Distance
152
• Braking distance is a function of speed, brake power,
gradient, condition and type of rolling stock, condition
of rails, curvature, wind speed etc.
• Since these factors are difficult to assess, trials are
conducted by RDSO to determine the EBDs of different
types of trains, locomotives etc. at various speeds and
results are published and circulated periodically.

Sighting Distance
153
• Sighting distance- is the distance over which the most
restrictive aspect of a signal is visible from the
locomotive cab.
• Every signal must be so located as to provide the
minimum SD necessary for it.
• After sighting a signal, the driver reacts to it and then
applies brakes (if required).
• Reaction Distance (RD)- is the distance travelled by the
train during this time. Therefore, SD should be equal to
or more than RD+EBD.

Sighting Distance for FSS
154
• For 2 aspect signals, since there is no pre-warning,
SD = RD + EBD
• For multi aspect signals, since there is pre-warning,
SD = RD only (because EBD is available between
the sighted signal and the next signal where the train may
have to stop).

Visibility of Signals
MULTIPLE ASPECT SIGNALS
• Distant Signal 400 Metres
• Inner Distant Signal 200 Metres (where provided)
• All Stop Signals 200 Metres
• Subsidiary signals - Visibility is not a criteria
If it is not possible to ensure 200 Metres (7 to 8
seconds) continuous visibility of any stop signal while
approaching it, a suitable speed restriction shall be
imposed.
155

IRISET 156

CHAPTER – 10 & 11
Isolation & Simultaneous Reception
157

ISOLATION
• ISOLATION- means an arrangement, secured by
the setting of points or other approved means, to
protect the line so isolated from the danger of
obstruction from other connected line or lines.

Isolation: Requirements
159
GR 4.11 Limits of speeds while running through stations
(1) No train shall run through an interlocked station at a
speed exceeding 50 kmph ... unless the line on which
the train is to run has been isolated from all other
lines by the setting of points and interlocking is such
as to maintain this condition during the passage of
the train.

Isolation required
• A line on which train movements at speeds higher
than 50 kmph are permitted should be isolated
from all connected lines.
• Passenger lines should be isolated from all
connected goods lines and sidings, whatever the
speed may be.

• The isolation of goods reception lines from sidings
is considered desirable.
• It is not necessary to isolate one goods reception
line from another goods or one passenger line from
another passenger line when dealing with speeds
of 50 kmph and less.

162
- Means of isolation
Isolation may be accomplished by -
–(a) connection to another line or long siding;
–(b) the provision of short dead end siding; or
–(c) the provision of trap
– ( d ) Slip siding
–( e) Catch siding

Siding, Dead End, Single Derailing Switch
163

When point is in normal then cross
movement is not possible
When point is in normal OR in
reveres position then cross
movement is always possible
from line I to line II
Line I
Line II
Line II
Line I
Hence line I and line II can be isolated
Hence line I and line II can not be isolated
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Derailing Switch, Dead End, Sand Hump
165

SLIP SIDING & CATCH SIDING
• For all gauges the maximum gradient permitted within
the station yard is 1:1200 .
• If steeper gradients are available in close proximity of
station yard then special type siding are provided.
• "SLIP SIDING" has to be provided, where the gradient
steeper than 1:100 & falling away from the station.
• SLIP SIDING protects block section,
• Prevents un authorised entry of vehicles into the next
block section.

• “CATCH SIDING” provided where the gradient steeper than
1:80 & falling towards the station.
• CATCH SIDING protects station section.
• Prevents un authorised entry of vehicles into station &Trap
uncontrolled vehicles coming from the block section
• "Slip siding" and `catch siding' points must be interlocked
with the block instruments,
• Normally point of such sidings should set for siding &
should not be used for shunting or stabling purposes.

Slip Siding
168

Catch Siding
169

Simultaneous Reception - GR 3.47
170
Taking off signals for more than one train at a time -
When two or more trains are approaching
simultaneously from any direction, the signals for one
train only shall be taken off, other necessary signals
being kept at on, until the train for which the signals
have been taken off has come to a stand at the station

Simultaneous Reception
171
GR 5.16 Shunting during reception of trains - When
signals have been taken off for an incoming train on
to a line which is not isolated, no shunting movement
shall be carried out towards points over which the
incoming train is to pass.

Simultaneous Reception
172
Line 1
Line 2 (Main Line)
Line 3
UNIVERSAL

POINT NORMAL
POINT NORMAL POINT REVERSE
POINT REVERSE
Overlap
Overlap
If Over shoots
SIMULTANEOUS RECEPTION IS POSSIBLE

POINT NORMAL
POINT NORMAL
POINT NORMAL
POINT REVERSE
Overlap
Overlap
If Over shoots
SIMULTANEOUS RECEPTION IS NOT POSSIBLE

175
Sand Hump

176
Sand Hump

SIMULTANEOUS RECEPTION & DISPATCH
• Taking OFF reception signal and dispatch signal for
different trains at the same time is called
simultaneous dispatch of trains.
• For simultaneous reception and dispatch of trains,
isolation and separate overlap for each movement is
ensured.

POINT NORMAL
POINT NORMAL POINT NORMAL
POINT REVERSE
Overlap
SIMULTANEOUS RECEPTION & DISPATCH IS POSSIBLE

POINT NORMAL
POINT NORMAL POINT NORMAL
POINT REVERSE
Overlap
SIMULTANEOUS RECEPTION & DISPATCH IS NOT POSSIBLE
No separate
Overlap

IRISET 180

CHAPTER -12
SYSTEMS OF TRAIN WORKING

Systems of Train working
182
 Chapter VII of GR describes the Systems of working
 Systems of Train working:
The Absolute Block System,
The Automatic Block System,
The One Train Only System.
The Following Trains System,
The Train-staff and Ticket System, and
The Pilot Guard System

The Absolute Block System
183
Essentials (GR 8.01):
 No train shall leave a Block Station unless LC has been received
from Block Station in advance
 On double line, such LC shall not be given unless
 The whole of the last preceding train has arrived
complete
 All necessary signals have been put back to On behind
the said train, and line is clear up-to FSS plus adequate
distance beyond it

• Unless otherwise approved under "approved
special instructions" ( sanction of Commissioner of
Railway Safety) block overlap shall not be less than
180 Mts in MACLS

The Absolute Block System
185
 On single line, such LC shall not be given unless
 The whole of last preceding train has arrived
complete
 All necessary signals have been put back to on behind
the said train
 line is clear up-to FSS plus adequate distance and it is
clear of trains running towards the station to which
LC is being given.

Station A
Station B
Block section Block overlap
Block section
Block overlap
P
P
FSS of Stn B
FSS of Stn A
LSS of Stn B
LSS of Stn A
Dist. of Stn B
Dist. of Stn A

The Automatic Block System
187
 Essentials for double line (GR 9.01):
 Line must be continuously track circuited
 Line between stations is divided into Automatic Block
Signalling Sections
 Entry into each Section is controlled by MACL stop signals
 Track Circuits control the aspect of signals
 OFF aspect only when line is clear up-to next
signal plus overlap (120 m)

188
 Essentials for single line (GR 9.03):
 Line must be continuously track circuited
 Direction of traffic only after LC has been obtained from
station in advance
 Train to start from the station only after direction of traffic
has been established
 LC shall not be granted unless line is clear up-to FSS plus
overlap

189
 Essentials for single line (GR 9.03):
 Line between stations is divided into Automatic Block
Signalling Sections
 Entry into each Section is controlled by MACL stop signals
 Track Circuits control the aspect of signals
OFF aspect only when line is clear up-to next
signal

190
Aspect Control:
 Yellow when one signalling section plus overlap is clear
 Green when two signalling sections plus overlap is clear (in 3
aspect territory)
 Double Yellow when two signalling sections plus overlap is
clear (in 4 aspect territory)
 Green when 3 signalling sections plus overlap is clear (in 4
aspect territory)

S.O
G
BLOCK
2
G
BLOCK
G G
S.O S.O
S.O
1 3 4
BLOCK
R G
G G
Y G
R G
G
Y
Y R
R G
Y Y
Y Y
FOR SIGNAL.1. TO ASSUME YELLOW - LINE MUST BE CLEAR FOR ONE BLOCK AND ONE OVERLAP
FOR SIGNAL.1. TO ASSUME DOUBLE YELLOW - LINE MUST BE CLEAR FOR TWO BLOCKS AND ONE OVERLAP
FOR SIGNAL.1. TO ASSUME GREEN - LINE MUST BE CLEAR FOR THREE BLOCKS AND ONE OVERLAP

192
 Minimum equipment of signals (GR 9.04)
Manual stop signals at stations
 Home
 Starter
an Automatic stop signal in rear of Home signal of the station
 one or more additional auto signals in between block
stations (GR 9.05)

193
 Points to remember:
 Track is continuously track circuited
 Signals display Off aspect normally when there are no trains
 Signals are replaced automatically to on with the passage of
trains past them
 Drivers are authorised to pass automatic signals after
observing certain precautions

194
 What happens if an Automatic signal is defective:
 Signal can be at ON due to TC failure or some other defect
 Driver should stop and wait in rear of signal
 one minute during DAY
 Two minutes during NIGHT
 If signal remains ON, inform Guard by whistle code & hand
signal and proceed at restricted speed (15 kmph or less) till
he reaches the next signal, then be guided by the aspect of
next signal

Modified Semi-Automatic Signalling Working
a. Under special instructions, one of the automatic
stop signals between two stations in the
automatic block signalling territory on Double
Line may be made as modified semi-automatic
stop signal in each direction.

• During abnormal conditions like fog, bad weather
impairing visibility, Modified Semi-Automatic Signal
may be worked by extinguishing ‘A’ marker in the
manner prescribed under special instructions and this
section shall also ensure that the ‘A’ Marker of the
Advanced Starter Signal of the station in rear and Home
signal of the station in advance shall also be
extinguished. (Provisions as per para 9.01 of GR shall be
ensured.)

MODIFIED SEMI-AUTOMATIC SIGNAL

Markers on Automatic signal
• Each Automatic Stop
Signal shall be
identified by its number
and provided with a
Marker consisting of a
white disc with letter ‘A’
in black.

Marker on Semi- Automatic sig
• A Semi-Automatic Stop
Signal shall be provided
with a Marker which shall
show a white illuminated
letter ‘A’ against a black
background when the
signal works as an
Automatic Stop Signal.

• Signal interlocked with a
level-crossing shall be
provided with an enamelled
yellow disc with letters 'G'
in black and an 'A' marker
light. The 'A' marker shall
be lit only when the gates
are closed and locked
against road traffic.

• Auto signal interlocked
with LC Gate and point

• Points are correctly
set, locked LC gate is
closed properly and
signal is working as
Automatic Signal

• LC gate is defective but
points are correctly set,
locked and signal is
working as Automatic
Signal

IRISET 204

CHAPTER 13
CLASSIFICATION OF STATIONS –A,B & C

Classification of stations
206
1. Stations shall, for the purpose of these Rules, be divided into
two categories
• Block Stations, and
• Non - Block stations.
2. Block stations are those at which the Driver must obtain an
authority to proceed under the system of working to enter the
block section with his train; and under the absolute Block
System consist of three classes-

Classification of Stations
Station
Block Station Non Block Station
Driver must obtain an authority to
proceed enter the block section
with his train
Class A
Class B
Class C
Class D
Stopping Places between
two consecutive block
stations ( do not form
boundary of any block
station)
Any station which cannot be worked under A, B,C or D class conditions:
Special Class : (MUST HAVE THE APPROVAL OF CRS: Commissioner
Railway Safety)

Classification of stations
208
Class A stations -Conditions for granting Line Clear at a
class `A` station—
• At a class `A` station on single line or double line, the line
shall not be considered clear and Line Clear shall not be
given, unless--
(a) the whole of the last preceding train has arrived
complete ;
(b) all signals have been put back to ‘on’ behind the said
train;
(c) the line on which it is intended to receive the
incoming train is clear up to the Starter and
•

(d) all points have been correctly set and all facing
points have been locked for the admission of the
train on the said line.
( e ) where Line Clear may not be given for a train
unless the line on which it is intended to receive
the train is clear for at least 400 meters beyond the
Home signal, or upto the Starter;

Conditions for granting Line Clear at a class ‘B’
station.––
• At a class ‘B’ station on double line, the line shall
not be considered clear and Line Clear shall not be
given, unless -
complete
• All necessary signals have been put back to ‘on’
behind the said train; and
(b) the line is clear -
• (i) at stations equipped with multiple-aspect
signaling - Up to the outermost facing points or the
Block Section Limit Board (if any)

• At a class ‘B’ station on single line, the line shall not
be considered clear and Line Clear shall not be
given, unless –
complete;
(b) all necessary signals have been put back to ‘on’
behind the said train; and
• (c) the line is clear- up to the Shunting Limit Board
or Advanced Starter (if any ) at the end of the
station nearest to the expected train, or
• up to the outermost facing points if there is no
Shunting Limit Board or Advanced Starter.

• At a class ‘C’ station on single line or double line in
multiple-aspect signalling, the line shall not be
considered clear and Line Clear shall not be given,
unless-
• (a) the whole of the last preceding train has passed
complete at least 400 meters beyond the Home
signal and is continuing its journey ; and
• (b) all signals taken ‘off’ for the preceding train
have been put back to ‘on’ behind the said train:
• Provided that on a single line, the line is also clear
of trains running in the opposite direction towards
the block hut from the block station at the other
end.

Class D stations or Non-block stations are stopping
places which are situated between two consecutive
block stations, and do not form the boundary of
any block section.

Equipment of signals
214
Manually operated Multi aspect signals (GR 3.27)
Class of
Station
Minimum
Equipment
Additional
Equipment
A
B
Does not exist
Distant, Home, Starter
Distant, Home
Adv Str / SLB
C

Comparison between class A & B stations
215
A’ class stations
• Exist only in 2 aspect
signalling.
• Now obsolete. Used only
under special circumstances.
• There is no station section.
• No shunting after LC is given.
• LC cannot be given to both
sides simultaneously.
• LC cannot be given unless
reception line is clear.
• Obstruction is protected by 2
signals
B’ class stations
• Exist in 2 aspect as well as in
multi-aspect signalling
• Most stations are B class,
more trains can be dealt
• There is a definite station
section
• Shunting is possible.
• No such restriction.
• No such restriction.
• Obstruction is protected by
one signal.

IRISET 216

CHAPTER -14
STANDARDS OF INTERLOCKING

218
Standards of Interlocking

Para No: 7.8.9 of IRSEM (Issue - July 2021): Table-3: Important Minimum Signalling Features
DETAILS STD I STD II STD III STD IV
Maximum
permissible speed
Up to 50Kmph Up to 110Kmph Up to 140Kmph Up to 160Kmph
Isolation See Notes
below
Required Required Required
Point Operation,
Locking & Detection
Point Machine Point Machine Point Machine Point Machine &
Direct Clamp type
with Thick web
switches
Train Detection
(Track circuit/Axle
Counters)
On all Run
through Lines
On all Running
Lines
On all Running
Lines
On all Running
Lines
MACLS
Signalling,Movemen
t authority
MACLS MACLS MACLS MACLS,
Movement
Authority
Block Working
(Absolute/Automati
c Signaling)
Permitted
(Including
Token
Working)
Permitted
(Excluding Token)
Permitted
(Excluding Token)
Or
4A Automatic
Permitted
(Excluding Token)
Or
4A Automatic

7 Double
Distant/Automatic
Signalling
Not
Compulsory
Required
(On sections where
Trains have a
Emergency Braking
Distance of more
than 1 Km)
Required
Or
4A Automatic
Signalling
Required
Or
4A Automatic
Signalling
8 Last Vehicle
verification
Not
Compulsory
Required at
stations with
centralized
operation or in high
density routes
Required Required
9 Relay/Electronic
Interlocking (RI/EI)
RI/EI RI/EI RI/EI RI/EI
10 Mobile Train radio
communication
(MTRC) or LTE or any
other Technology
Not
Compulsory
Desirable Desirable Required
11 ATP
(ETCS/TCAS/TPWS)
with Cab Signalling
for SPAD mitigation
Not
Compulsory
Desirable Desirable Required
12 Centralised Traffic
Control (CTC)
Not
Compulsory
Desirable Desirable Desirable

1.Isolation: Isolation is not compulsory. Extract
from “Rules for Opening of Railway Lines – Rule
36” is given below
2. At no station at which isolation has not been
provided through running trains shall be permitted
unless the conditions laid down in the second
paragraph of the rule 4.11 of the General Rules are
complied with.

• Extract of GR 4.11. Limits of speed while running through
stations.-
• No train shall run through an interlocked station at a speed
exceeding 50 kilometers an hour or such less speed as may be
prescribed by approved special instructions unless the line on
which the train is to run has been isolated from all other lines
by the setting of points or other approved means and
interlocking is such as to maintain this condition during the
passage of the train.

• In every case in which trains are permitted to run
through on a non isolated line , all shunting shall
be stopped and no vehicle unattached to an engine
or not properly secured in accordance with General
Rule 5.23 may be kept standing on a connected
line which is not isolated from the through line.

• All Passengers running Lines shall be isolated from all Goods
lines or Sidings connected thereto.
• All goods running Lines may be isolated from all sidings
connected there to.
• It is not necessary to isolate one goods receiving line from
another

IRISET 225

CHAPTER -15
OPERATION OF POINTS

OPERATION OF POINTS
02.06.2020 227

Electrical point operation

Point in general
1. Points, which are used to divert trains from one line to the
other, will become a source of danger unless adequate
precautions are taken, points are said to be facing when
they are approached from the toe end.
2. Even a casual study of points will indicate that for
movements in the facing direction more precautions should
be taken.
3. The points should be correctly set, i.e., the closed switch
should be housed correctly against the stock rail and the
open switch should be well clear of the corresponding stock
rail.
4. The points should be prevented from becoming unlocked
during the passage of a train.
02.06.2020 229

Location of point and range of operation
1. Points must be so located that movements over them shall
be within the view of the cabin or other location from which
they are worked, unless an approved alternative for direct
vision by cabin man, e.g., electric indication, is provided.
2. The distance at which points may be worked by rodding is
must not exceed 320m except where the stroke at the lever
tail is not less than 200 mm in which case the above distance
may be increased to 460m
02.06.2020 230

Speed of train over point
1. Points in which the only equipment is a gauge tie plate and a
padlock for locking them in position, and which may or may not
be locally operated are said to be un-interlocked.
2. A speed restriction of 15 KMPH is imposed over them in the
facing direction and of 50 KMPH in the trailing direction.
3. Unrestricted speed in the trailing direction is, however,
permitted on the straight road if the points are interlocked with
signals, even though locking and detection are not provided.
231

IRISET 233

CHAPTER -16
INTER CABIN CONTROL

CABIN

LEVER FRAME

INTERLOCKING

Principles of Slotting:
• The term `Slotting' has come to mean in signalling parlance the
control of a signal by source or sources other than the operating
source.
• The control of signals by more than one source is much more
frequent than in the use of points.
• A slotted signal cannot be taken `OFF' unless the controls from
all remote locations have been operated, but it should be
possible for any one of the controlling agencies to replace the
signal to its most restrictive aspect.
INTER CABIN CONTROL
02.06.2020 238

The purpose of slotting is two fold:
•To ensure that the points located on the line controlled by the
signal including the overlap are set correctly and facing points
locked and the line is clear, before the signal is taken off and
•These conditions are maintained until the train movement is
completed.
•In other words, no other conflicting or fouling movement is
allowed to take place and the points are not altered until the
train movement is completed.
INTER CABIN CONTROL
02.06.2020 239

Types of Controls Slots
1. The following types of Controls/Slots are in
general use in mechanical installations:
(a)The mechanical lever lock worked by key
transmitted electrically
(b)The electric lever lock
(c)The electric signal reverser post type
2. The design, construction and maintenance of
the various types of slots are dealt with
elsewhere.
02.06.2020 240

INTER CABIN CONTROL
241

IRISET 242

CHAPTER -17
LOCATION OF SIGNALS

Placement of Distant Signal
• Distant Signal shall be placed at an *adequate
distance in rear of the first Stop Signal.
• *Note: Such an adequate distance shall not be less
than 1 kilometre in Single Distant Territory
• In Double Distant territories: On sections, where
Emergency Braking Distance (EBD) of more than 1.0
km is to be catered for, a second Distant signal shall
be provided. Such a Distant signal shall be placed at
an adequate distance of not less than 2 kms in rear
of First Stop signal and Inner Distant Signal shall be
placed at a distance of not less than 1 km in rear of
First Stop signal.

Placement of Stop Signals
• Home Signal: The Home Signal shall be placed in rear of all
connections, if any, on the line to which it refers.
• The Home Signal shall be placed at not less than *180
metres in rear of the points up to which the line may be
obstructed, after line clear has been granted to the station
in rear.
• Starter Signal: When one Starter Signal is provided for each
converging line, it shall be so placed as to protect the
adjacent running line or lines.

• Intermediate Starter Signal: An Intermediate Starter
Signal shall be placed clear of fouling marks in rear of
the points, if any, which it protects.
• Advanced starter -It shall be located at a distance of
not less than 120 meters from the outermost points
in the case of Single Line section. This distance shall
be reckoned from the starter in case of Double Line
Section.

• Gate Stop Signal: shall be located at not less than
180 meter (in MACLS territory) in rear of the gate,
which it is protecting. Gate Signal shall be provided
with a marker consisting of a yellow coloured disc
with letter 'G’ in black.

DESIGNATION AND LOCATION SIGNALS
on Single line
248

250
DESIGNATION AND LOCATION SIGNALS
on Double Line

 DOUBLE DISTANT TERRITORY
Normal aspect of distant signal is attention
Post of distant signal is of is painted alternate yellow & black strip
Distant signal Placed at distance of 1 Km in rear of existing distant
Goods warning board is not required.
Station B
P
FSS of Stn B
LSS of Stn B
P
Distant. Inner Distant.
1KM 1KM

P
FSS
LSS
Distant.
1Km
GWB
1.4Km
SINGLE DISTANT SIGNAL TERRITORY

• Aspects-Sequence Chart
• Aspect sequence chart of various signals shown on
SIP as per movement of train .
• For each directional ( up /Dn ) signals aspect
sequence chart provided
• When a Signal is displaying the 'Stop' aspect, the
signal next in rear shall not display a less restrictive
aspect than 'Caution'.

Distant
signal
Home signal
Main Line
Starter
Loop Line
Starter
Advanced
Starter
Indication to Loco
Pilot
Yellow Red - - - Stop dead at Home
Double
Yellow
Yellow Red - -
Stop dead at Main
line Starter
Green Green Green - Green Run through on
Main Line
Double
yellow
Yellow with
Route
indicator
- Red -
Stop dead at loop
line starter
Double
Yellow
Yellow with
Route
indicator
- Yellow Green
Run through via
loop line
ASPECT SEQUENCE CHART

S.No.
Distant
signal
Inner
Distant
signal
Home
signal
Main
Line
Starter
Loop Line
Starter
Advance
d Starter
Indication to
Loco Pilot
1.
Double
Yellow
Yellow Red - - -
Stop dead at
Home
2. Green
Double
Yellow
Yellow Red - -
Stop dead at
Main line Starter
3.
Green Green Green Green - Green Run through on
Main Line
4.
Double
Yellow
Double
yellow
Yellow
with Route
indicator
- Red -
Stop dead at
loop line starter
5.
Double
Yellow
Double
Yellow
Yellow
with Route
indicator
- Yellow Green
Run through via
loop line
ASPECT SEQUENCE CHART ( DOUBLE DISTANT SIG )

IRISET 256

CHAPTER -18
LEVEL CROSSING GATES

258
Level Crossings

Level crossing Gate

What and Why
261
 When road traffic crosses the rail traffic at the same
level, they are known as level crossings.
 At level crossings, the road is brought upto the level of
rail table and guard rails are provided to ensure
clearance for wheel flanges.
 LCs become necessary because the alternative of
over/under bridges is very expensive

262
 A level crossing will have an arrangement to stop
road traffic on either side of the X - ing (except at D
class X - ings).
 This arrangement can be swing gates, lifting barriers
or even a chain across the road.
 It will have check rails to keep the flange-way clear.
 Provision of Warning signs are mandatory on either
side of the LC for warning road users

Norms for deciding Class of a LC
263
 Classification is done considering class of road,
visibility and volume of road and rail traffic
 Number of trains per 24 hrs. multiplied by number of
road vehicles per 24 hrs. gives the Train Vehicle Units
for the LC.
 Category I, TVUs more than 3000, Category II , less
than 800m visibility to road users and TVU more than
2500 manning should be done.
 TVUs over 20,000 Qualifies for interlocking.
 Min TVUs should be 1 lakh to become eligible for
ROB/RUB on cost sharing basis.

LC Gates are classification depends on
•Depends on nature of road
•The no. of road vehicles passing
•The no. of trains passing.
02.06.2020 264

LC Gates are classified
1. SPL – Class - More than 50,000 (TVU)
2. ‘A’-Class – More than 30,000 (TVU)
3. ‘B-1’ – Class – More than 25000 (at least 750
buses/day) [TVU]
4. ‘B-2’- Class- More than 20000 (TVU)
5. ‘C’ – Class – All there road user
6. ‘D’ – Class – For cattle crossing.
“Sensor will be taken once in three year, 7 days
consecutive, on an average”.
02.06.2020 265

1. TVU- Train Vehicle Unit (train unit x vehicle unit)
2. Train, Motor vehicle, bullock carts & tongues – 1 unit
3. Cycle rickshaw & auto rickshaw – ½ unit
4. Visibility of manned gate – 5M.
5. Fencing parallel to the track – 15M
6. Gate lodge –6M from center of track
7. Speed Breakers – 20M from center of track
8. Height gauge – 8M from center of track
9. Gate post – 3M from center of track
10. TVU is more than 6000 or L.C.Gate visibility is poor –Un manned
gate is converted into Manned gate.
Additional information For L.C.Gates
02.06.2020 266

Classes of level crossings
267
• Special class : TVUs > 50,000
• A’ class : TVUs > 30,000 and <50,000
• B1 class : TVUs > 25,000 and <30,000
• B2 class : TVUs > 20,000 and <25,000
• C’ class (Md) : Category I > 3000 Cat II > 2500
• D’ class : Cattle crossing
(TVU’s > 20,000 Shall be Normally kept open to Road Traffic
C’ class if interlocked, shall be normally kept open to RT)
If average number of trains is less “say up to 14 in a day”, the
normal position can be changed to “Open to road traffic”
regards less of TVU’s

Sl.
No.
DETAILS
CLASSES
Other
Stipulations
Special
Class
> 50,000
‘A’
> 30,000
< 50,000
‘B1’
> 25,000
< 30,000
‘B2’
> 20,000
< 25,000
‘C’
Cat I > 3000
Cat II > 2500
1 Interlocking Gates with Signals
a
If within station
limit
Should be interlocked with station signals
Should be
interlocked with
station signals
b
If outside the
station limit
Should be interlocked with gate signals
Should be
interlocked with
gate signals
Sub Urban &
Auto section all
to be
interlocked
c Normal position Open to road traffic
Open to road
traffic if
Inter Locked
2 Telephone Communicated from the Gate lodge
a
Within or
outside station
limit
Telephone to be provided with the ASM's office with all the
manned LC Gates
02.06.2020 268

Sl.
No.
DETAILS
CLASSES
Other
Stipulations
Special
Class
> 50,000
‘A’
> 30,000
< 50,000
‘B1’
> 25,000
< 30,000
‘B2’
> 20,000
< 25,000
‘C’
Cat I > 3000
Cat II > 2500
3 Warning bell or Hooters operated by App Trains
a
Within or
outside station
limit
Should be provided
Should be
provided
4 Type of Lifting Barrier
a
Within or
outside station
limit
Electrically Operated Lifting Barrier EOLB in SU
5 Approach Locking
a
To be provided in Sub Urban section
Others - DA Locking -30 sec
To be provided
in SU
Others - DAL-30
sec for EOLB
02.06.2020 269

Gate Signals
270
A Gate Stop Signal shall be fixed at an adequate distance
from the gate.
The Gate Stop Signal shall be provided with ‘G’ marker
except where prohibited under special instructions
Multiple aspect/modified lower quadrant signalling, a Stop
Signal at 180 metres from the gate and a Distant signal at 1
km in rear of the Stop Signal may be provided.

271
On sections provided with Multiple aspect signalling,
when the interlocked gates are situated between
Distant and Home signal-
(a) The Gate Signal shall be located at 180 metres in rear
of the gate;
(b) The Distant Signal shall be located at not less than 1
km in rear of the Gate Signal and will function as
Gate Distant as well.
Interlocked Gates within Station Limits

Gate Stop
Signal
Gate Stop Signal in
Automatic Block Territory
(Letter A shall be lit only
when gates are closed
and locked against road
traffic)
Refer GR 3.17
A AG
Gate Stop Signal in semi-
automatic territory
(Letter A shall be lit only
when gates are closed
and locked & points are
correctly set and locked.
Letter AG shall be lit
when points are
correctly set and locked
but gate is open or
defective.)
G G
A
272

Level crossing located within station
limits in MA signalling
273
P
(3) (2) (1)
S.O
120M
1KM.B.D
B.O
180M
UP STARTERS
STARTER
UP.ADV.
UP DN
DN.DISTANT
BOARD
1.4 KM
DN.HOME
GOODS WARNING
The gate shall be interlocked with down Homes,
up starter, and up Homes

Level crossing located within station
limits in Double Line MACLS
274
BSLB
180M
1.4 KM
P
1KM
The gate shall be interlocked with down Homes, up starter,
and up Homes

L.C gate is between the down Homes
and up advance starter
275
P
180M
1KM
180M
P
1KM
1.4 KM
The gate should be interlocked with down Homes and up
advance starter only

276
P
(i)
STARTER
UP.ADV.
HOMES
ROUTING
HOME
DISTANT
1KM
1.4 KM
180M
P
180M
1KM
L.C gate is little away from the down Homes, The gate interlocked with down
Home signal and the up advanced starter and with routing homes if required.
If the gate is just in rear of the Homes the Home may be shifted at 180m in rear of
the gate
L.C gate is between the down Home
and Down Distant

277
Sr. Distant Gate cum
Distance
Home Remarks
1 YELLOW RED ----- Stop at Gate Signal
2 GREEN YELLOW RED Stop at Home Signal
3 GREEN DOUBLE
YELLOW
YELLOW / YELLOW
WITH ROUTE
Going to be received on
main line / loop line
4 GREEN GREEN GREEN Train is on run through via
main line

IRISET 278

CHAPTER-19
SECTION CAPACITY

Section Capacity
• The maximum number of trains that can be dealt on
a given section of Railway during the period of 24
hours, is called the Section Capacity.
• It is expressed as number of trains each way on
single line
02.06.2020 280

Scott’s FORMULLA:
• 24 x 60
C = ------------ x E x 1/2
T + t
Where, C = Section Capacity
T = Running Time of slowest train to pass Ruling Block
Section
t = Average Time required for Sginalling and Block
operations
E = Efficiency factor (80)
Section Capacity
02.06.2020 281

Section Capacity
18.11.2020 282
Tp = Running time of Passenger train
Tg = Running time of Goods train
Cg = Section capacity of Goods train

• On single line section the line capacity can be
augmented by improving `T' and `t' of Scott's formula,
as well as the `E' factor, T can be reduced by
Section Capacity
02.06.2020 283

– Reducing the length of block section by providing additional
crossing stations.
– Increasing speed by providing better mode of traction, tracks,
rolling stocks and signalling.
`t' may be reduced by introducing
o Higher standard of interlocking
o Token less block instruments
o Panel interlocking
o CTC and Automatic signalling
Section Capacity
02.06.2020 284

Section Capacity
• `E' (Efficiency factor) can be improved by proper time
tabling, punctuality, staff efficiency, upkeep of
equipments,
• Efficient operation, adequate number of loop lines,
suitable length of block section and IBS on double
line, etc.
• Simplification of rules, training of staff is also the
factors to improve the operating efficiency.
02.06.2020 285

IRISET 286

CHAPTER -20
Principles of Signal Engineering

Principles of Signal Engineering
• Failsafe feature
• Normal Danger system
• Zero Sighting Distance
• One aspect one indication
• Visibility from the place of operation
• Overlaps
• Operation friendly
• RAMS
• Uniformity of signals
• Continuous visibility to Driver
• Independent Block & Yard signaling
• Minimum signals on a route

Fail Safe Design
• Safety of passengers and efficiency of operation being
the twin purposes for which fixed signals are installed.
• Each and every apparatus and circuit employed in a
signalling system shall be so designed that a failure
occurring in any of the component parts of the system
results in the signal or signals controlled by the system
displaying their most restrictive aspects.

RAMS
• Reliability, Availability, Maintainability and Safety shall be
important consideration in the design of apparatus, circuits
and systems
• The aspects of fixed signals shall be distinctive and
unambiguous
• One aspect shall have but one name and one indication,
conversely for a given indication the same aspect shall be
used everywhere and at all times.

• The action required by a signal indication shall be definite
and capable of easy implementation.
• Each and every signal shall afford the sighting distance
required, of it.
• The number of fixed signals provided shall be the minimum
for each route.
• The overlaps required for each system of aspects shall be
clearly specified.
RAMS

Essentials of Interlocking
Essentials of Interlocking: Equipments provided for the
operation and control of signals, points, etc., shall be so
interlocked and arranged as to comply with the following
essentials;
(a) It shall not be possible to take 'OFF' a Main stop signal
or a Subsidiary signal, unless all points in the route,
including overlap and isolation(as applicable), are
correctly set and locked and all interlocked level crossing
are closed and locked against public road, and relevant
tracks are unoccupied by vehicles and clear for the line
on which the train will travel.

Essentials of Interlocking
(b) After such signal has been taken „OFF‟, it shall neither
be possible to move any points nor unlock the route,
including overlap and isolation, nor to open any
interlocked gates until the concerned signal is
replaced to 'ON' position.
(c) It shall not be possible to take 'OFF' any two signals
simultaneously, which can lead to conflicting
movements. 7.6.2 Route Holding (Approach Locking
& Back Locking

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