This paper presents a methodology for testing, evaluation and determination of overlay thickness required for a given pavement section. The overlay design procedure presented makes use of some of the recent developments for analysis and design of asphaltic concrete overlays. The evaluation of in-service pavements includes the use of the deflection parameters developed by testing of the existing pavements with known geometry for determining the moduli of various pavement layers and the required overlay thickness. The method utilizes empirical values and VESYS structural subsystem as an integral approach complementary to each other. Six pavement sections across the State of North Carolina were selected for deflection testing. Deflection parameters were developed to characterize the deflection data from these pavement sections. In addition, VESYS structural system was used to develop nomographs for the interpretation of the measured deflection basin parameters. These nomographs were used to backcalculate the layer moduli form deflection parameters and known layer thicknesses using iterative solutions. The backcalculated layer moduli from these nomographs correspond to the climate conditions that happen to exist during the time of testing and must therefore be adjusted to other climatic conditions. A procedure for such an adjustment is also included in the design procedure. Many different methods have been developed for determining an overlay thickness. These methods can be categorized in three groups : component analysis, deflection based, and analytically based. A mechanistic procedure is described in this paper. This procedure is based on the data and findings of a previous research and has been used to evaluate in-service pavements in North Carolina using Falling Weight Deflectometer (FWD) deflection parameters. The procedure includes four major parts : (a) FWD deflection parameters and data collection, (b) back-calculation of layer moduli, (c) adjustment of layer moduli and (d) prediction of overlay thickness. For the covering abstract of this Conference see IRRD abstract number 853851.