1) Signalling systems provide safety and direction for train movements using signals and switches. Early systems used flags but were replaced by colored light signals. 2) Signals are classified by their function like stop signals, warner signals, and disc signals. They are also classified by their location like outer signals, home signals and starter signals. 3) Interlocking systems ensure the safe operation of signals and switches through mechanical or electrical linkages to prevent conflicting train movements. Centralized traffic control systems operate from a control room.

1. Dr. ABHISHEK JINDAL
Signalling, Interlocking, Tractive
Power and Tractive Resistance

2. SIGNALLING
• Movement of trains from 1
track to another – by points
and crossings and turnouts.
• Driver of train is informed by
– Signals.
• Initially – policemen and
security guards with red and
green flags to inform driver.
• Later colored light signals
were introduced.

3. Signalling -
Purpose
• To provide direction and indication to
driver regarding proper setting of
switches.
• To provide safety and efficiency to
shunting operation i.e. shifting of train
from 1 track to another.
• To facilitate flow of traffic and ensuring
safe distance b/w trains running on same
lines and in same directions.
• To provide safety to passengers and staff
by preventing collision amongst trains.
• To give directional indication at diverging
joint.

4. Signalling -
Classification
• According to Functions:
– Stop, Warner, Disc, Colored Light
• According to Location:
– Outer, Home, Starter, Advance
Starter
• Special:
– Routing, Repeater, Co-acting,
Calling – on indicators and
Miscellaneous.

5. Signalling –
Signals
according
to
Functions
Stop or Semaphore:
If anything goes wrong with signal
mechanism, the signal shows
STOP position.
• Positions of arm – Horizontal
and Inclined.
• Horizontal – signal is ON –
danger so STOP.
• Inclined – signal is OFF –
proceed.
• At night – RED and GREEN
lights.

6. Signalling –
Signals according
to Functions
Stop or Semaphore:

7. Signalling –
Signals
according to
Functions
Warner Signal:
• To warn the driver of
corresponding position of the
semaphore signal.
• Similar to Semaphore signal
except that a V – notch is
provided at free end.
• For night operation – ON
position by RED light, OFF
position by GREEN light.

8. Signalling –
Signals according
to Functions
Warner Signal

9. Signalling – Signals according to
Functions
Disc or Ground Signal:
• Shunting signals used for shunting operations at low
speeds.
• Circular DISCS with red band on white background.
• RED and GREEN lights are used for STOP and PROCEED
indication.

10. Signalling – Signals
according to Functions
Disc or Ground Signal

11. Signalling –
Signals
according
to
Functions
Colored Light Signals:
• Automatically operated and give
indications by electric lighting.
• Height of vertical post sufficient – in
line with driver’s eye.
• RED light STOP.
• YELLOW or AMBER light PROCEED
cautiously.
• GREEN light PROCEED.

12. Signalling –
Signals
according to
Functions
Colored Light Signals

13. Signalling –
Signals
according to
Locations
Outer Signals:
• Train in motion requires certain
minimum time before it can be
brought to halt.
• Factors – speed of train, gradient,
weight of train and braking power of
locomotive.
• Distance from station sector.
• Signal provided - Outer Signal.

14. Signalling –
Signals
according
to Locations
Home Signals:
• Signal controls movement of
train before entering station
premises.
• To protect stations and
junctions.
• By operating the signal train is
given permission to enter the
platform.

15. Signalling –
Signals
according to
Locations
Starter Signals:
• Signal controls movement of train as
they leave the station premises.
• By operating the signal train is given
permission to leave the platform.
• Unless the signal is lowered – trains
cannot leave the station.

16. Signalling –
Signals
according
to Locations
Advance Signals:
• Signals in form of Discs and
used for carrying out shunting
operation.

17. Signalling – Special
Signals
Routing Signals:
• Signals for main and
branch lines are fixed on
same vertical post. Such
signals – Routing signals.

18. Signalling – Special
Signals
Repeating Signals:
• When visibility of main
signal is obstructed
due to intervening
structures, information
of main signal is
repeated with the help
of Repeating signal.

19. Signalling
– Special
Signals
Co-acting Signals:
• When visibility of main
signal is obstructed due to
bridges, tunnels or some
other reason, a duplicate
signal is provided on main
signal on a lower level.

20. Signalling – Special Signals
Calling On Signals:
• When main signal stops the train, a calling on
signal, a short arm fixed on same post at a
lower level, permits the train to proceed
precautiously.

21. Signalling – Special Signals
Indicators:
• Furnish special informations.
• Provided where sight of driver is obstructed.

22. Signalling – Special Signals
Miscellaneous Signals:
• Fixed Boards indicating Maximum Speed.
• Special signals for Marshalling Yards.

23. Centralized Traffic Control System
• System controls movement of the train from control room
from which POINTS and SIGNALS are operated.
• 1st introduced in USA.
• Driver has to follow the indication given by signals prior to
and near the point of execution.
• If driver does not follow, STOP signal automatically operates
and train is stopped.

25. Centralized
Traffic
Control
System
Advantages:
• Track defects easily located.
• Push buttons operates POINTS and
SIGNALS.
• Most satisfactory for single line
operation.
• Controller can take instantaneous
decisions thus increasing track capacity.
• Track can be used constantly at
maximum speed.

26. Signalling
System
Communication with train for traffic management.
• Absolute Block:
– Railway line is developed into Block Section.
– One train can move at a time.
– All block stations are linked in series for
exchange of information.

27. Signalling
System
• Space Interval:
– In this system b/w 2 trains there is only 1
clear section. B/w these sections 1 section is
always clear.

28. Signalling System
Time Interval:
used in emergency when block system
not working.
Only when telegraphic message is
received from next station that line b/w 2
stations is clear, train is allowed to move.
Pilot Guard:
When message to next station cannot be
conveyed.
1 pilot goes with 1 train to next station
and comes back with another train, thus
train is allowed to leave only when guard
comes back with other train confirming
line is clear.

29. Interlocking

30. Interlocking
• Relationship between various levers operating the
SIGNALS and POINTS to eliminate contrary effects.

31. Interlocking
Basic principles:
– Loose wagons from any part of the
yard should not be able to obstruct
the line.
– Unless the line is set properly, it will
not be possible to ON the signal for
any approaching train.
– It would be impossible to lower
signals for admission of train from
opposite or contrary direction to the
same line at same time.

32. Interlocking
- Methods
• Key System
– Indirect Interlocking
-- Used in a number of small stations in India.
• Single Lock Key System
• Double Lock Key System

33. Interlocking -
Methods
• Route Relay System:
– Points and signals for movement of
trains are electrically operated.
– Most modern and sophisticated system.

34. Interlocking -
Methods
• Tappet and Lock System
– When levers are required to be interlocked to
prevent conflicting movements this method is useful.

35. ATS
(Automatic
Train
Supervision
system)
• Computer system that totally manages and controls train
operation and train route based on the schedule during train
traffic control.
• This equipment is indispensable for achieving high-density
operation.
• It is a versatile system that can also accommodate a large-
scale route in spite of a simple configuration.

36. Tractive Power
and Tractive
Resistance
• Train – 2 units
– Locomotive
– Rolling Stock
– Power – by locomotive.
– Rolling stock – passenger bogies or goods
wagons.

37. Energy for
Traction
• Locomotives – Power from steam generated
in a large boiler.
• Till 70’s almost all traffic – steam engines.
• Diesel
• Electric
• Presently:
– 64% freight – based on diesel.
– 31% electric transmission.
– Only 1% by steam locomotive.

38. Wheel of
Locomotive
• 2 types of wheels:
• Driving – connected with piston of engine. Coupled to
each other.
– Power of locomotive – number of driving
wheels
– Smaller diameter of wheels – increase tractive
power, reduces speed.
– Larger diameter of wheels – reduce tractive
power, increases speed.
• Idle –
– Distribute self load of locomotive on track.
– Number Increases with increase of load in
locomotive.

39. Track Resistance
• Resistance due to FRICTION = 0.0016 W
• Resistance due to RISING GRADIENT.
• Resistance due to HORIZONTAL CURVE.
• Resistance due to SPEED OF TRAIN.
• Resistance due to WAVE MOTION= 0.0008 WV
• ATMOSPHERIC RESISTANCE.
• W= Weight of Train in tonnes.
• V = Speed of Train in Kmph.

40. THE END