IRSE News 138 Oct 08.pdf

TECHNICAL
IRSE
Nowadays safety case work is often
done by safety case specialists rather than
being done by signal engineers as an
integral part of the design, development
and implementation processes. In
fairness it has to be acknowledged that
suppliers have by and large incorporated
EN5012x standards into their core
processes for system development and the
result, whilst still paper intensive, appears
to be well integrated. In contrast, systems
application projects that involve safety
case work often appear to generate large
volumes of paperwork which provide
limited added assurance, and which err
very much on the side of caution without
sufficient regard to the cost and reliability
implications.
The IRSE addresses this problem to
some extent for younger engineers by
incorporating modern safety competence
in the IRSE examination syllabus, but we
suggest that the Institution could do more.
It might set clear expectations for
EN5012x/Yellow Book safety processes
for generic product development of
signalling systems, for generic application
of signalling systems and for applicationspecific
signalling projects.
It might create an expectation that
engineering safety work is done by the
designers as part of the design process,
not by others within a project.
It might give clear guidance on how
to improve assurance and reduce the
scale of documentation.
Practical steps might include:
setting up a technical committee to
agree the expectations;
promoting these expectations as IRSE
agreed good practice;
requiring evidence of relevant safety
engineering experience in all designers’
and engineering managers’ IRSE
licences.
RADICALLY REDUCING
TRACKSIDE TESTING
Testing is an activity that we tend to accept
as a necessary part of bringing any
signalling system into service. This is true,
but we urgently need to take a hard look at
what is being done, and the price that
comes with it.
If we are honest with ourselves, we do
testing to compensate for deficiencies in
specification, design and implementation.
If we had greater confidence in the outputs
from earlier life-cycle stages, testing would
be less important and take less time.
Resignalling projects can generate hundreds
of test logs during testing - yet we claim
that the systems are designed to safety
integrity level SIL 4. How can this be?
Testing cannot build quality and safety
into a project at the end, nor should it be
presumed to do so. Conventional wisdom
says that you cannot inspect quality into a
product, only remove the defects. Quality
and safety are built in through high
standards of design and construction.
The on-track testing regime takes an
unacceptable amount of time and
constitutes an unacceptably high cost.
In Great Britain long bank holiday
weekend possessions on the main line
railway are coming under the scrutiny of
the Office of Rail Regulation as part of the
drive to move towards a 24/7 railway.
Signal engineering work is one of the most
high profile activities undertaken during
such possessions, disrupting the railway at
vast expense with scarce labour resources.
It is quite simply an unsustainable way of
carrying on.
These are compelling reasons for rethinking
the testing of signalling systems.
This is not the first time that testing has
been the focus of attention, but useful
outcomes always seem to have eluded us,
and we are still testing systems in
substantially the same way as we have
done ever since the Clapham accident
almost twenty years ago. Here again the
IRSE could take the initiative and set some
top level targets.
Design, design review and approval
processes should be such that we do not
expect the testing phase to find any design
errors. This change needs to avoid the
trap of incorporating yet more layers of
labour-intensive design checking.
Any testing that is required in order
to validate the design should be factory
based, that is it should not need to be
performed intrusively on the operational
railway.
Checks on site, that is on the
operational railway, should be restricted
strictly to installation quality assurance
and simple correspondence tests.
These streamlined testing regimes
should be in routine use within five years.
What this may mean in practice is a
complete re-think of the process of
designing signalling systems right through
to commissioning. But we can start by
taking some simple steps:
reviewing the errors (and their causes)
that the existing testing regime
identifies;
revising design and implementation
processes to catch errors at the point
where they occur;
providing guidance on how system
architecture and automated design
processes and tools can help reduce
the incidence of errors and therefore
reduce the extent and intrusiveness of
checking and testing processes;
formalising the streamlined, efficient
processes.
ENERGY EFFICIENCY AND
CARBON EMISSIONS
REDUCTION
It may well be true that signal engineers
have paid insufficient attention to
reliability. It is certain that we have given
virtually no attention at all to energy
efficiency or to carbon emissions, at least
in the era when power has been cheap
and plentiful. Some signal engineers will
still remember the days when power was
not readily available at mechanical signal
boxes and all sorts of clever ideas were
implemented to minimise power
consumption. But then we destroyed our
green credentials by throwing the expired
batteries down the embankment for nature
to contend with!
Now energy, carbon emissions and
sustainability are all key considerations for
almost any human enterprise, and
signalling and telecommunications
engineering is not excluded. It might of
course be argued that, since railways are
one of the more environmentally friendly
forms of transport, they need not be a
priority for us – and since signalling and
telecommunications systems are not major
users of energy, they are well down the list
of priorities even within the rail industry.
But remember please the demise of the
British car industry to which we referred
earlier, and their view that unreliability was
something that had to be lived with. The
railway industry cannot afford to put its
head in the sand, regarding itself as being
the acceptably green form of transport for
the foreseeable future. Every industry has
to play its part in making improvements,
and if we do not we will find that the car
industry makes rapid strides and
competes with us for green credentials
while we stand still.
6
Issue 138 October 2008
IRSE
NEWS