The variability in travel times is a very important feature in determining the arrival of the passenger at the destination within a given travel time threshold and can be noted as one of the most important characteristic for travel time reliability that is an increasing concern of travelers, because it allows travelers to make better use of their own time. In this paper reliability in multimodal travel by consideration of focuses on the passenger travel times is investigated. For this aim, the variations passengers encounter in a multimodal network with respect to the capabilities of different services is analyzed. In order to identify the sources of variations and improve the service in an integrated manner a methodology based on process capability indices is presented. The fuzzy set theory is also integrated with process capability indices to increase the sensitiveness and flexibility of route and station reliability and to ease definition of specification limits. The proposed methodology is applied in Istanbul to investigate the reliability of travel times of multimodal travels of passengers using a specific subway line.