The value of the effects associated with unpunctuality are currently not well known, as there has been little interest in valuation of punctuality effects up until a few years ago. Therefore, this in-depth research project was undertaken. It is aimed at providing all the elements necessary to estimate these values, and to calculate the impacts of punctuality improvements. The results have been used to develop a robust operational methodology which enables the user to assess possible alternative investments aimed at improving the quality of the suburban rail services to and from Paris. The methodology is needed to assist the decision-making process regarding possible alternative projects (combinations of measures) to improve the punctuality of suburban rail services.