Proceedings 2002/2003 - IRSE

58
SIGNALLING CONTROL CENTRES TODAY AND TOMORROW
Radio Block Centre (RBC). In the simplest option this
can be a one-way link, with the interlocking providing
signal aspect information to the RBC, which then
translates this into movement authorities which are
sent to the trains using GSM-R radio. Again there is
no change from the viewpoint of the control centre.
The RBC will have a facility for entering information
about temporary speed restrictions, but there is no
fundamental need for this to be integrated into the
signalling control centre system.
ETCS Level 2 without lineside signals (conventional
block lengths) is a more fundamental
change to the signalling system. However, route
locking and movement authorities are still based on
fixed block lengths equivalent to conventional signal
spacing, using track based train detection systems
(track circuits or axle counters). There will also
inevitably be uniquely numbered lineside marker
boards at each block section boundary, to give the
driver a precise target for stopping the train in
normal operation, and to allow unambiguous verbal
instructions to be given by the signaller when train
movements have to take place during signalling
failures. These marker boards will replace signals as
the route entrances and exits, and so it will be
logical to show them on the signaller's workstation
screens instead of signals. By treating the marker
boards as “virtual signals” and showing them as
signals on the workstation screen, it would be
possible to implement this level of ETCS with no
changes to control centre software or working
practices. In practice some small changes on the
screens may be desirable to differentiate clearly
between “real” and “virtual” signals.
ETCS Level 2 without lineside signals (short
block lengths) is the next step to be considered. As
with the previous option, lineside marker boards
delineating the block sections can be treated as
“virtual signals”, with route setting between marker
boards. On the signaller’s workstation screens, each
short block section will require a “virtual signal”
symbol and a train describer berth, and this will
mean that the physical length of railway displayed
on a workstation screen will be reduced. There may
also be an increase in signaller workload when
manual route-setting is in use. These problems can
be mitigated in various ways, eg showing only
selected marker boards on overview displays, and
allowing the signaller to select entrance and exit
points more than one block section apart – this is
already available as a “long route” option in IECC. In
practice, of course, automatic route setting would
play a large part in exploiting the additional capacity
made available by this version of ETCS.
ETCS Level 3 is currently regarded as being a
long way into the future, but when Level 2 without
signals is well established and a high level of train
fitment is achieved, the financial and reliability
benefits of eliminating track based train detection
will become very attractive. Level 3 is usually
associated with moving block signalling, but there is
no reason why train location information should not
be converted back into fixed block occupation
states, to provide a system which is functionally
equivalent to Level 2. This might seem a retrograde
step, but it would give the cost savings of Level 3
with the minimum amount of change to existing
operating rules and systems. Level 3 with true
moving block is another matter altogether, and
would require a much more fundamental recreatethink
of how the systems (and people) in control
centres interact with the signalling.
ENHANCED CONTROL CENTRE
FUNCTIONALITY FOR ERTMS/ETCS LEVEL 2
AND ABOVE
In the preceding section, the theme has been that
even the “highest” levels of ETCS could be implemented
with minimal impact on signalling control
centre systems. However, to restrict our ambitions in
this way will be to ignore some exciting new
possibilities of adding value by exploiting the new
facility of dependable two-way communication with
the train by:
• using information from the train in the control
centre;
• integrating additional facilities provided as a part
of ETCS;
• adding extra facilities beyond those provided by
ETCS.
Figure 7 illustrates how this will lead to a “triangular”
relationship between the control centre, the
interlocking and the RBC.
USING INFORMATION FROM THE TRAIN IN THE
CONTROL CENTRE
Signalling control systems are used to monitor and
control train movements, but in traditional signalling
they actually only deal with lineside equipment. The
part of the system which works in terms of trains is
the Train Describer, and this has to work by
deducing information about train movements from
the lineside equipment states. With ETCS Level 2
and above, the signalling system now includes the
RBC which is receiving regular updates of information
from every train. This is much more accurate
and comprehensive information which could be
used by the signaller and automatic route setting
systems. It includes:
• train position, length and speed (already known
from train detection information, but with very
limited precision);
• train identity and performance characteristics
(currently assumed from timetable information
without any means of checking validity);
• ETCS modes of operation (entirely unknown to
conventional signalling).
The more precise information about train
characteristics, position and speed could allow
automatic route setting systems to make much more
accurate predictions of future train movements, and
enable further optimisation of route setting
strategies to minimise train delays. This and the
other information would in some circumstances also
be very useful to the signaller, but the interesting
question is – how to present it? The usual representation
of each train on the signaller’s workstation is
the train’s headcode in a train describer berth,
together with one or more occupied track circuits.