Service dependability of transit systems: a case study

The authors present a study of the application of an `ad hoc' dependability model to a real railway transit system, the Baiano-Naples route of the Circumvesuviana S.p.A. This is a single-track line of considerable length, in which the probability of occurrence of more than one failure in a trip is not negligible. The model is able to provide reliable results, and can be used to perform sensitivity analyses, which make it possible to indicate how the service dependability can be improved, and how much the improvement would be. Such analyses have shown that a large improvement cannot be achieved by increasing the reliability or maintainability characteristics, whereas some design modifications would appreciably increase the system dependability.