Information Technology Reference
In-Depth Information
From the standpoint of the railway system's design: Switching to AC
would entail taking into account all the constraints stemming from the AC's
inherent limitation. A deep study would need to be undertaken for each
type of interlocking existing on each national network in order to assess the
impacts on the system design on the one hand and on the overall balance
sheet on the other hand. Such an economic study would involve comparing
the expected benefits for the rolling stock with the costs tied to the redesign
of the infrastructure (for example, an absolute block limits throughput) and
the associated operating procedures (more frequent need of procedures to
check that track sections have been cleared, for instance).
From the safety standpoint: The TC provides additional benefits that
should not be underestimated, i.e.:
- Detection of broken rails, an advantage likely to grow in importance as
concrete sleepers become more widespread on HSL (fast destruction of
the sleepers);
- Detection of metal obstructions fallen onto the track, option to use the
TC shorting bar or clip in emergencies or in maintenance (protection of
a track section with workers) . . .
- Phasing out TC would not respect the legal requirement to be “GALE”
(Globally At Least Equivalent) in changing the system, from the stand-
point of preventing the hazard of running over a BR at speed (function
not fulfilled by AC). As a consequence, the loss of broken rail detection
would require as-yet undefined compensating measures, e.g. close mon-
itoring and grinding of rails with attendant higher maintenance, to be
implemented in order to meet the GALE requirements, with a proba-
bilistic point of view. Phasing out one for another system needs a new
formal validation of the interlocking modules with the new type of detec-
tor (TC or AC).
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Modelling
Estimation of the propagation of rail defects A global modelling of the two
situations allows determining the pertinence domain (economic eciency)
while taking into account all the maintenance costs and the associated risk.
From a technical point of view, preventive grinding allows the elimination
of early surface defects before they deteriorate thus extends the rail lifetime
(augmentation of 30and has a positive effect on tamping durability.
From an economic point of view it remains to be determined whether
the maintenance costs are reduced and the great investments related to rails
replacement can be delayed.
From a safety point of view, preventive grinding doesn't allow the elimi-
nation of the internal defects and the possibility of a broken rail apparition
has to be considered. Consequently, to estimate the residual risk with AC,
we will take into account:
