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Abstract. The objective of the present paper is to determine the thickness of bituminous overlay on the top of a flexible road pavement using a mechanistic-empirical approach. The thickness of the overlay has been estimated on the basis of allowable deflection at the overlay-pavement interface to withstand anticipated axle load repetitions during its service life, while the strength of existing flexible road pavement has been estimated on the basis of pavement surface deflection. The pavement with overlay in the present paper has been considered as a two-layered system, which has been transformed into a homogeneous medium by using Odemark’s method to determine the vertical interface stress at pavement-overlay interface using Bousenesq’s theory. The thickness of overlay for different pavement deflection and axle load repetitions have been obtained using present method and was compared with Asphalt Institute method (AI). The rate of increase of overlay thickness observed in the AI and present method for different axle load ranges are reasonably close. Therefore, the sensitivity of pavement deflection on overlay thickness is comparable between the two methods. The Base Layer Index (BLI) has been estimated using a mechanistic approach for different overlay thickness obtained from AI and present method which shows reasonable convergence. The significant convergence of results between two methods justify the reliability of proposed method as a reliable overlay design approach. It was found from sensitivity analysis that the modulus of the bituminous mix is more sensitive to affect the overlay thickness than axle load repetition, if other parameters remain unchanged.
