Mass-transit system service quality: tradeoff analysis on reliability, maintainability and logistics

Service quality is influenced not only by intrinsic reliability and maintainability but also by logistical factors such as: the number of operations reserves of spare trains; the number of repair facilities; fleet size; average recovery times after perturbations; and spare parts. Operators are looking for service quality commitments from manufacturers. However, only intrinsic reliability and maintainability, and to some extent, service reliability, are determined by the manufacturer's design. This paper addresses quantitatively the dependence of service quality on intrinsic reliability and maintainability, and logistic variables. Analytical models, based on Markov chains, are used to derive the corresponding relationships. Sensitivity analyses can then be performed. Tradeoffs can be assessed quantitatively between several solutions for achieving a given service quality target at different costs. On the basis of such a tradeoff analysis. The effort toward a higher service quality can be guided in a life-cycle cost perspective. Also, reliability and maintainability apportionments can be performed which are derived from the service quality objective. Logistic parameters are seen to play a key part. Accordingly, the manufacturer which does not control maintenance may find it inappropriate to commit to a service quality level, but may commit, instead, to reliability and maintainability levels that, under precise assumptions on the logistics, result in the desired service quality.