Signalling by w6WLescw



             Philip Meurant
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
   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
    Signalling: Basic Principles

•   Track Circuits: Identify the location of trains.

•   Interlocking: Prevents conflicting train movements, ensures locking of signals and

•   Signals: Visually displays information to train drivers.

•   Train Stop: Operates in association with signals to prevent trains overrunning an

•   Points: Diverts trains at junctions or yards.

•   Signal Box / Control Centre: Operates the train movements.
           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
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
 – 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
 So the next question is how do you do that?
              Interlocking cont

•   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.
               Interlocking cont
    Relay Interlockings

•   Relays have eliminated lever locking frames, pulleys, signal wires
    and rods from interlockings and replaced with relays and electric

•   Initiated by control from Signal Boxes or Control Centres, signals and points are
     controlled by fail safe type relays.
               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
             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
             Interlocking cont
   – This type of interlocking interfaces to the field equipment via relays.
   – Control can be by push button or VDU panel
             Control Systems
•   Mechanical
     – Large lever frames
     – Control equipment over a short area
        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.
      Control Systems cont

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


                   Headway is a minimum:

                  Distance or Time

                   for a minimum journey time.

              – Signals should be equally time spaced
             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
 Headway vs Braking Distance at 80km/h
GE 62 (Suburban Train)
                                 200m CLEAR        CAUTION        STOP            STOP

                                                          440m                           EMU
GW 16 (900m Freight)                                          1720m      77 seconds

                       CLEAR         MEDIUM        CAUTION        STOP            STOP

                                                 836m                                    EMU
                                                Headway          91 seconds
GW 40 (1500m Freight)                            2036m
        CLEAR       MEDIUM           MEDIUM       CAUTION         STOP            STOP

                                        1216m                                         EMU
                                      Headway     109 seconds
               Signal Design


   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
        Signalling the Future
European Rail Traffic Management System
-Overlay to Existing Signalling System.
-Movement Authorities through Eurobalise.
-Train Integrity & Position by Track Circuit

-Computer for train management
-Brake pipe interface
        Signalling the Future


-No more Trackside Signals Required.

-Movement Authorities through GSM-R.

-Train Position via Eurobalise
    Signalling the Future

ERTMS/ETCS                      LEVEL 3

- Movement Authorities through GSM-R

- Train position through GPS Tracking
Thank You

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