Signalling

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Signalling

• Philip Meurant

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This presentation will cover

• A brief history of Signalling in NSW
• Very basic principles
• The different types of Interlocking Systems in
  Use
• Control Systems
• Signal interpretation

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Signalling A brief History

• 1855 Railway line in Sydney opened
• Initial application of token working, then
  time table working until 1879.
• 1877 A campaign for a safeworking system was
  passed
• 1878 Emu Plains collision occurred just before
  the new system introduced
• 1879 Manual Block Instruments introduced
• 1881 First mechanical interlocking frame at
  Burwood
• 1888 Electric tablet
• 1891 Electric train staff
• 1910 Power Signalling introduced
• 1913 Double light system
• 1915 3 position upper quadrant signalling
• 1924 Colour Light signals
• 1928 All electric miniature lever frame

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Signalling Basic Principles

• Track Circuits Identify the location of trains.
• Interlocking Prevents conflicting train
  movements, ensures locking of signals and points.
• Signals Visually displays information to train
  drivers.
• Train Stop Operates in association with signals
  to prevent trains overrunning an authority.
• Points Diverts trains at junctions or yards.
• Signal Box / Control Centre Operates the train
  movements.

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Track Circuits

• Track circuits are used to locate trains in the
  system. Information is feed from the track relay
  to vital control circuits and/or to the
  Interlocking to provide train protection and
  locking.
• A basic track circuit shown below is made up of
  the following components-
• A power source
• A variable resistance
• A relay
• Insulated rail joints to separate rail sections

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Interlocking

• What is an Interlocking?
• In general terms an interlocking is a location
  where plain track ends and trackwork with points
  and crossings complicate train movements. These
  areas are likely to be-
• Junctions where two or more main lines meet.
• Complex yards or sidings are encountered. These
  may be at larger towns or depot facilities.
• An interlocking provides for complex train
  movements and shunting of trains. It provides for
  the protection of multiple train movements within
  a localised area.
• So the next question is how do you do that?

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Interlocking cont

• Mechanical
• Very early mechanical interlockings consisted
  of large levers, pulleys, steel wire to control
  signals and channel iron (roding) to operate
  points.
• Levers had direct mechanical connections to the
  signalling equipment
• Area of control was limited.
• Locking Frames
• In mechanical interlockings, locking between
  signals and signals, or signals and points
  were carried out using levers and a tappet
  system in the locking frame.

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Interlocking cont

• Relay Interlockings
• Relays have eliminated lever locking frames,
  pulleys, signal wires and rods from
  interlockings and replaced with relays and
  electric circuits.
• Initiated by control from Signal Boxes or
  Control Centres, signals and points are
  controlled by fail safe type relays.

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Interlocking cont

• Computer Based Interlocking (CBI)
• CBI interlocking are now the current standard in
  NSW.
• There are currently three types in use.
• These are vital safety validated systems and fail
  safe.
• Solid State Interlocking Microlok

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Interlocking cont

• Solid State Interlocking
• This type of interlocking interfaces to field
  equipment by a communications to trackside
  modules. The modules interface by input/output
  logic either to relays (track relays etc) or
  directly drive signals etc.
• Control can be by push button or VDU panel

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Interlocking cont

• Microlok
• This type of interlocking interfaces to the field
  equipment via relays.
• Control can be by push button or VDU panel

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Control Systems

• Mechanical
• Large lever frames
• Control equipment over a short area locally

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Control Systems cont

• Push Button Panel
• Push / Pull button control (entry/exit system,
  non vital)
• Track circuit and signal indications displayed by
  diagram lights
• May be local or remote from the interlocking
  connected by a secure communications line.

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Control Systems cont

• VDU
• Software controlled (non vital system).
• Interfaces with the Interlocking via secure comms
  line.
• Provides VDU screen interface with point and
  shoot control.

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Signal Design

• Headway
• Headway is a minimum
• Distance or Time
• for a minimum journey time.
• Signals should be equally time spaced

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Signal Design

• Headway can only be specified knowing
• The type of train (performance)
• Length of train
• Allowed speed of train (if not line speed)
• Stopping / Non Stopping
• Station dwell time
• Sighting Distance of Signal

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Headway vs Braking Distance at 80km/h
GE 62 (Suburban Train)
200m Sighting
CAUTION
CLEAR
STOP
STOP
EMU
77 seconds
GW 16 (900m Freight)
CAUTION
MEDIUM
CLEAR
STOP
STOP
EMU
91 seconds
EMU
109 seconds
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Signal Design

• Overlaps
• An overlap is a margin of safety past a STOP
  signal
• Overlaps are
• Trip braking distance for electric trains in
  train stop fitted areas
• Nominal distance in country areas
• Catchpoints are considered an overlap

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Signalling the Future
European Rail Traffic Management System
ERTMS/ETCS LEVEL 1
EUROBALISE -Overlay to Existing Signalling
System.-Movement Authorities through Eurobalise.
-Train Integrity Position by Track Circuit

• TRAINBORNE
• Receiver
• Computer for train management
• Tachometer
• Brake pipe interface

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Signalling the Future
ERTMS/ETCS LEVEL 2
-No more Trackside Signals Required. -Movement
Authorities through GSM-R. -Train Position via
Eurobalise
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Signalling the Future

• ERTMS/ETCS LEVEL 3
• - Movement Authorities through GSM-R
• - Train position through GPS Tracking

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• Thank You