<p>The objective of this study was to assess the difference in performance of flexible pavement system between using conventional elastic and viscoelastic properties of asphalt mixtures in pavement design. Three types of asphalt mixtures, namely Dense-graded, Polymer-modified Gap-graded (P-Gap), and Asphalt Rubber Gap-graded (AR-Gap) mixtures, were considered in this study. At first, a conventional Mechanistic-Empirical pavement design was carried out with fundamental design inputs, material properties, layer thicknesses, loading conditions, design traffic, etc. Next, |E*| dynamic complex modulus was determined and employed to characterize the viscoelastic properties of asphalt mixtures using master curves and Prony series parameters. Furthermore, a finite element model (FEM) was developed, wherein the viscoelastic properties of asphalt mixtures were assigned to the wearing course in the pavement model. Critical strains obtained from the FEM revealed that tensile strains obtained using viscoelastic properties were approximately 41% higher than the strains obtained from elastic analyses. However, no significant difference in compressive strain was noticed. In addition, critical strains were used to predict the design life of pavement with 90% reliability. It was found that the design life of all the mixtures with viscoelastic properties was at least 56% lower than that of the elastic analysis. Among all the asphalt mixtures, AR-Gap mixtures showed the highest difference, 77% in design life due to its higher viscous behavior. It is envisaged that the study findings would provide an important understanding pertaining to the accuracy in performance prediction when the design is carried out on the premise of viscoelastic properties of materials.</p>