Thus, to accurately predict fatigue cracking, it is necessary to include both crack initiation (Ni) and crack propagation(Np). However, crack propagation (Np) is often not directly considered in various
existing mechanistic-empirical (M-E) fatigue analysis approaches such as the Asphalt Institute (AI, 1982), Shell (Shell, 1985), and MEPDG (NCHRP, 2004)