The effect of transient dynamic loading on flexible pavements was estimated. Transient dynamic loads within a tire-to-pavement contact area are characterized by continuously increasing or decreasing local dynamic contact stresses, depending on vehicle speed. A transient dynamic load model was successfully incorporated into a three-dimensional finite element model. Dynamic flexible pavement responses to one pass of a heavy vehicular load through a dual-tire assembly were calculated. Results of this study indicate that the flexible pavement response at different pavement temperatures varies depending on whether the analysis was quasi-static or dynamic, where the mass inertia and damping forces by the transient local dynamic loads are considered in the equation of motion. Results also show that the time-dependent history of the calculated pavement responses in the dynamic analysis is more comparable to measurements in the field. The transverse and longitudinal tensile strains at the bottom of the hot-mix asphalt and the compressive stress at the top of the subgrade are underestimated when the mass inertia and damping forces exerted by the transient local dynamic load are ignored.