RAIL INFRASTRUCTURE
Infrastructure in a rail environment is made up of the following
components: the tracks (railway lines), Perway (bridges, platforms),
signaling technology (robots, points machines and relay rooms),
telecommunications systems (surveillance cameras, PA systems and
CTCs) and the electrical systems (cables, power lines, gantries).
Infrastructure plays an important role in commuter rail with
regard to the safe movements of trains. The need for safer and
more effective train control is important as the number, speed,
mass and length of the trains increase.
Signalling:
Signaling is defined as a system that controls the movements
of trains to and from (communication system between the train
and the operating (CTC). Signaling permits the safe movements
of trains at maximum permissible speed and minimum headway. It
is found at station areas but also interconnects the signaling
between stations.
The signaling system is composed of the following essential mechanisms:
- Points
Points are defined as track equipment, which enables trains
to move from one track to another. They are mainly used for
the purposes of enabling the movement of one line to another.
Points are very important in that they allocate and control
the movement of trains on specific lines expecially where
two lines are joined or at a junction. In addition points
prevents unauthorised movements of trains including unlawfully
deviating a train from its intended direction thereby causing
an accident or collision with another train.
- Set of Points:
- A Signal
A signal simply put is a robot next to the railway track
and functions the same way as any robot on our roads. It is
defined as an apparatus, which provides visual information
to the driver of a train about the availability of a specific
line, and whether is it safe to proceed or not. It is a communication
system between a train driver and a control centre to:
- Regulate and safeguard the movements of trains at crossings
or depending on circumstances.
- Ensure a safe distance between trains on the same line.
The following different types of signals are in use today:
- Colour light signals
- These are the automatic robots controlled from a CTC.
- Semaphore (mechanical) signals
- This type of signal is mechanically operated by means of
pulling a lever. This signal is used to direct trains
- travelling in the "up" or "down" direction.
Centralised Traffic Control (CTC)
A CTC is what is known as a 'control room' a central point where
a number of signals are controlled. The main facility in the CTC
is the control panels that enable operators to monitor and control
remotely the movements of trains in the local area or within a
CTC area. The panels are like a map on the wall and on the table
with sets of points, route map, diagrams and displays.
Diagrams and displays are used to display train information such
as the direction it's headed to operators in a clear and helpful
manner. These diagrams are diagrammatic representations of the
geographic layout of the physical tracks with illuminated route
lights to show which signal the driver is facing.
Train describer
It is a system, which is used to identify trains, assist the
CTC operators controlling these trains. It's main function is
to display the number allocated to a particular train on the CTC
diagram, thereby showing the operator the location of the train.
This number follows the train as it progresses from station to
station on the diagram in predetermined steps. The operator knows
at any point in time the location of all the trains under his
control.
Interlocking
An interlocking mechanical relays which combines and interlocks
the points, signals and track circuits to ensure that no conflicting
movements takes place. Interlocking is a control mechanism, which
acts as an interface between the operator (CTC), and the equipments.
Track circuits (e.g. train detection system). This equipment
is used to detect the occupation of a track by a train in a safe
and reliable manner.
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