Signalling Principles
Transcript of Signalling Principles
-
7/27/2019 Signalling Principles
1/36
Signalling Principles
In Plain English
(Reference to masculine gender alsorefers to the female gender!)
Tony Howker March 2011
-
7/27/2019 Signalling Principles
2/36
A system that Prevents collisions and
derailments!
A Definition of Signalling
(The tool to Manage the Operation of the Railway)
-
7/27/2019 Signalling Principles
3/36
Look what happens in a collision or derailment!
-
7/27/2019 Signalling Principles
4/36
How does Signalling do this?
A signalman operator of the Signalling System,
gives instructions to a Driver of a train.
The Instructions started with Handsignals but
then put signalmen controlled coloured lights or
planks of wood on the top of poles and expectedDrivers of Trains to obey their meaning!
-
7/27/2019 Signalling Principles
5/36
Handsignal
being
exhibited by
the
Signalman.
(He was
called a
policemen
in thosedays
hence the
nickname
for a
signalman
wasBobby)
-
7/27/2019 Signalling Principles
6/36
-
7/27/2019 Signalling Principles
7/36
-
7/27/2019 Signalling Principles
8/36
-
7/27/2019 Signalling Principles
9/36
-
7/27/2019 Signalling Principles
10/36
-
7/27/2019 Signalling Principles
11/36
-
7/27/2019 Signalling Principles
12/36
A Few Definitions
I think that you know what I mean and
you think I know what you mean but
just to be sure!
-
7/27/2019 Signalling Principles
13/36
Definitions Route A section of railway line from
a fixed signal to the next
signal may containpoints ornot may continue past nextsignal ifoverlaps are provided
Route
Overlap
-
7/27/2019 Signalling Principles
14/36
Definitions Signal A means of displaying
an Authority toProceed and the driver
is aware of the limit of
that Authority.
-
7/27/2019 Signalling Principles
15/36
Definitions Points
Facing Trailing
A moveable section of the
railway that allows trains todivert onto or converge
from another section of
railway
Facing point complete with Facing Point Lock
Diverting Lines
Trailing point Converging Lines
-
7/27/2019 Signalling Principles
16/36
Definitions Overlap
In the Rear of a Signal
In Advance of a Signal
An Overlap is a section
of railway line beyond astop signal that must be
clear before a train can
be given permission toapproach that signal
from the rear.
Length often varies between a nominaldistance and braking distance
Overlap
In AdvanceIn the Rear
-
7/27/2019 Signalling Principles
17/36
-
7/27/2019 Signalling Principles
18/36
DefinitionsNormal & Reverse These originally described the
position of a mechanical lever in a
frame and thus related to theposition ofpoints. When relating
tosignals they describe the signal
being at Stop or Red. Nowadays
Normal is a statement that theequipment or system is in a
quiescent state awaiting a
command to control signalling
equipment. Pulling the lever
controlling signals moved the
signal to give proceed authority to
the Train Driver. (Always
assuming that the interlocking
allowed the movement)
This is the
NORMAL
position
This is the
REVERSE
position
-
7/27/2019 Signalling Principles
19/36
Definitions Interlocking (Original) Originates from the meaning
to interlock between 2 ormore levers in a mechanical
frame
10Worked by Lever
11Worked by Lever
To Move Lever 10 from Normal to Reverse Lever
11 has to be Normal. If Lever 11 is Reverse, Lever
10 cannot be moved from the Normal position and
therefore is Locked Normal in the lever frame. Hence
the word Interlocking
Worked by Lever 9
Normal Position of 11 points willallow a train to pass along the Main
Line The diagram shows the
Normal lie of the points.
If 11 points are Reverse then the
points will allow a train to move
from the Loop Line to join the main
Line by moving Lever 9 to the
Reverse position
Loop Line
Main Line
-
7/27/2019 Signalling Principles
20/36
Definitions Interlocking (Modern
Definition) & Controls
Can be done using relays, computers
or a combination of both.
This is the name given to the
Equipment and System that
allows the signalling to becontrolled in a safe manner and
the information given to the Train
Driver to also be correct and safe.
The Interlocking also receivesinformation from the trackside.
Today the terms interlocked by
and controlled by are
synonymous and both could be
replaced by required by.
Interlocking
TC A TC BTC C TC D
TC ETC F
TC G
TC H
23101A
101B25
TC J
Indications
Controls
Signalman
RequestsDiagram or VDU
-
7/27/2019 Signalling Principles
21/36
The Main PrinciplesGiving unequivocal permission to the driver that it is OK for him to proceed
means that -
The line is clear of any other train or obstruction along this route to the limitof Authority
The Signalman will not alter the line or route as long as the authority is valid
If we withdraw the Authority to proceed, we will not be able to alter the line
or route until the train that was given the authority has come to a complete
stand
-
7/27/2019 Signalling Principles
22/36
Principles for allowing a Main signal
to show a proceed aspect The line must be clear between the
route entrance signal and the exit
signal ahead The overlap must also be clear
Any lines that converge should also
be clear to the protecting signal
All points in the route must be set,locked and detected in the right
position
Trailing points in the overlap at the
exit signal must be locked and
detected normal
The entrance signal of any directly
opposing routes must be proved at
Red and free ofApproach Locking
-
7/27/2019 Signalling Principles
23/36
-
7/27/2019 Signalling Principles
24/36
Approach LockingBefore we discuss Approach Locking a little piece of Physics!Trains are heavy and travel at quite a reasonable speed and create substantial kinetic
energy
Because this kinetic energy needs to be dissipated, braking to a stop means that trainscannot stop as quickly as cars or trucks they need distance which also means time.
Therefore our trans cannot be driven on-sight as a car or truck can. All signals
capable of showing a stop aspect need to have an advance warning signal at least
Braking Distance before the stop signal. This is often known as a Distant signal.
So when our signalman withdraws a movement authority (i.e. he replaces a signal to redor stop) he cannot rely on the fact that the train driver will have enough time or distance
to be able to bring his train to a stop at the red signal, especially as the warning (or
distant) signal will have been showing an indication that stated that the next signal was
at proceed. This means that the requirement to hold the route locked until the train has
come to a stand must be carried out by Approach Locking
Approach Locking can only be released by proving the train is at a stand at the red
signal or that the train has passed safely through the route which has remained locked
even though the signal at the entrance to this route has been replaced to red in front of
the train.
-
7/27/2019 Signalling Principles
25/36
Approach Locking
15A 3A 2A 1
When this signal at RedThis signal
shows Caution
Braking DistanceBraking Distance
This signal shows
Proceed at line speed
This signal shows Red
Signal 15 Cleared to ProceedThis signal shows
Proceed at line speed
This signal shows
Proceed at line speedThis signal shows Red
Signal 15 replaced to stop
Train within Braking Distance and
cannot stop before 15 Signal
Route ahead of Signal 15 now Approach Locked only released by
Train at a stand at 15 signal (usually done via a timer having run say 3
minutes), or train passing through route.
-
7/27/2019 Signalling Principles
26/36
Further Principles
Associated with Locking Approach Locking
Route Holding
Before a signal can clear the
approach locking must be
proved as being applied so
that it is available if
required.
The same applies to route
holding it must be proved
to be applied before thesignal can clear to a proceed
aspect.
-
7/27/2019 Signalling Principles
27/36
Train Separation The other Principle besides
locking is Train separation.
This is achieved by only allowing
one train at a time into a particular
piece of railway line. This sectionof line is often called a Block It
may or not be equal to Braking
Distance. (Probably longer)
Block Block & Braking Distance
Braking Distance
Braking Distance & Block Braking Distance & Block Braking Distance & Block
-
7/27/2019 Signalling Principles
28/36
-
7/27/2019 Signalling Principles
29/36
In Plain Language
We have just defined the fundamental principles
of Signalling
Interlocking Principles
&
Train Separation Principles
-
7/27/2019 Signalling Principles
30/36
Interlocking Principles
No route can be established unless that route is free of any opposing or
conflicting movements or locking
Any points within the route shall be free of locking or set in the required
position
The route should be unoccupied by trains or other obstructions before the exitsignal can be allowed to show a proceed aspect
Any points in the route shall be locked and detected in the required position
Any Overlap at the exit signal shall be clear of trains and any opposing or
conflicting locking Once a proceed aspect has been given to the driver it shall not be possible to
alter the route
It shall be possible to withdraw the authority given to a driver (re-placing the
entrance signal to stop) however it shall not be possible to alter the locked
route until the train has come to a stand or has passed through the route
Finally before allowing a signal to show a proceed aspect to the driver, it must
prove that the route ahead is locked and that the approach locking should be
primed and ready to be activated.
-
7/27/2019 Signalling Principles
31/36
Train Separation
Only one train shall be allowed in one section of line at a time (Block
Signalling)
Trains need time and distance to brake to a stand from the allowed line speed
signalling should allow for preliminary caution signals and not force drivers
to drive on sight like a car or truck
-
7/27/2019 Signalling Principles
32/36
A few extra comments
You will note that I have kept to the basic Principles of Signalling,
deliberately not differentiating between speed or route signalling or theaspects shown to a Driver.
Neither have I shown any principles for the application of any sort of
Automatic Train Protection System.
The equipment used for detecting whether a line is clear or obstructed is
outside the scope of signalling principles hence the idea of Plain English
-
7/27/2019 Signalling Principles
33/36
Remember who the Customer is for
our Signalling
-
7/27/2019 Signalling Principles
34/36
-
7/27/2019 Signalling Principles
35/36
-
7/27/2019 Signalling Principles
36/36
THE
ENDof MovementAuthority!