Pre-print, Working paper: An earlier draft of 6th October 2010 by Gaudry and Quinet, entitled Optimisation de l’entretien et de la régénération d’une infrastructure: exploration d’hypothèses, benefitted from comments by Bernard Caillaud and Matthieu de Lapparent and was presented without econometric tests at the Kuhmo Nectar Conference on Transportation Economics in Stockholm on 1st July 2011 under the title “Joint optimization of continuous maintenance and periodic renewal”. The authors thank Marc Antoni, Richard Arnott, David Meunier and Yves Puttalaz for discussions or comments, Cong-Liem Tran for computing assistance and are grateful to Société nationale des chemins de fer français (SNCF) for financial support and for allowing inclusion in this version of estimates based on databases constructed by Michel Ikonomov and Pascaline Boyer. Exploratory estimates obtained from fixed form regression specifications were presented at the Kuhmo Nectar Conference on Transportation Economics in Berlin on 21st June 2012 through David Meunier’s good offices.