The empirical approach to design depends solely on previous experiences and experiments, and on the other hand, the mechanistic approach to pavement design is to calculate graphs and tables during the process of design. Mechanistic approach in pavement design goes a step forward. Mechanics theory is used to predict traffic load and environmental conditions. The use of vertical compressive strain was first suggested by Kerkhoven & Mormon (1953) on the top of the subgrade as a criterion for establishing failure to reduce permanent strain. Saal & Pell (1960) suggested the use of horizontal tensile deformation at the bottom of the asphalt layer to minimize fatigue cracking. These and many other suggestions and publications have been part of research by institutions, states and agencies to improve the ME approach in pavement design. The most recent ME-based method was the design (NCHRO, 2004) of the NCHRO 1-37A. this incorporated nationally calibrated models to predict disruption induced by traffic load and the environment