Fatigue of reinforced concrete structures is often not considered for civil engineering structures due to the fact that dead loads of reinforced concrete structures are very high (for case of normal strength concrete) while live loads on these structures are relatively small which leads to very small stress variations during service duration of the structure. However, particularly for bridge structures with increased use of high strength concrete and increase in traffic loads this scenario is reversed and fatigue verification of these structures becomes much more important for the safety. This paper attempts to present a probabilistic framework for reliability assessment of existing bridges along with reliability-based calibration of fatigue design factors and present a case study for Cret De l’Anneau viaduct in Switzerland.