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Fatigue is considered the main damaging phenomenon at « average » temperature in flexible pavement structures. A fatigue damage model is thus the first step in applying a mechanistic-empirical approach to sizing. This paper highlights the main elements of fatigue models in order to thoroughly understand the various calculation tools available for a mechanistic-empirical sizing application. The signification of the various coefficients of the models is described and interrelations are established. An analysis is proposed to improve the representativeness of the fatigue life span law of the material. All calculation tools for mechanistic-empirical sizing use the Wöhler fatigue curve. Both fatigue curve coefficients are at the core of the models and describe the specific performance of the tested bituminous material families. Processing the results of a classic fatigue test to exclude biased effects will substantially modify the values of these two coefficients. It is demonstrated that the life spans determined from raw results are overestimated. [ABSTRACT FROM AUTHOR]