Each technology of track circuits (TC) or axle counters (AC) has its own domain of pertinence. Neither should be rejected out of hand. In the current state-of-the-art, neither of the two solutions allowing detecting the presence of trains is perfectly safe; signalling plant implicitly integrates the possibility of transient failures of the chosen solution. The TC, through its occupancy detection function, provides, especially on high traffic or high speed lines, a higher level of safety because of lower risks from human intervention, as much in maintenance, particularly corrective maintenance, as in degraded mode operation. Moreover, it ensures a continual check of the electrical integrity of the track. The TC's reliability is all the better when the traffic is great and/or that the traction system is electric (typically 10-7/h/TC on HSL (high speed line)). Moreover, the TC is well suited to traffic increase, since it allows the block to be permissive and sectional release in signal boxes. With the TC's, the safety level isn't coupled with the track maintenance policy, in particular regarding grinding. The AC provides, in France, for low-traffic lines, an economical solution to the control of clearing of long sections, without the risk of deshunting, albeit at the price of a stricter route locking (absolute block, no sectional release and so on) and greater operating complexity, in the event of disturbance or failure. The rate of failure internal rail defect rate is particularly low in this case. The preventive grinding has been proven to minimise rail defects, to extend rail service life, to reduce the maintenance costs of the track but cannot give the guaranty of no broken rail (internal defect) on highly loaded tracks. Preventive grinding would require new technologies with high production output at low costs, as it is still large time slot consuming. Safety: The broken rail detection issue will however remain, and will have to be solved, in particular for high speed lines. In general, the replacement from one type by an other type of detector, keeping all else constant, can lead to 'deterministic'' hazardous situations and has to be compensated. For example, the loss of broken rail detection would require as-yet undefined compensating measures, e.g. close monitoring and grinding of rails with attendant higher maintenance, to be implemented in order to meet the globally at least equivalent (GALE) requirements, with a 'probabilistic' point of view. Phasing out one for another system needs a new formal validation of the existing interlocking modules with the new type of detector.
Complementarity between axle counters and tracks circuits
Komplimentarität zwischen Achsenzähler und Spurschaltungen
2011
12 Seiten, 6 Bilder, 3 Quellen
Aufsatz (Konferenz)
Englisch
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