Characterization of pavement materials in the three hierarchical design levels of the proposed mechanistic-empirical pavement design (MEPD) guide involves application of the dynamic modulus technique for asphalt concrete and the resilient modulus for unbound materials. This approach, if adequately implemented, is expected to improve the road design processes. The advance design level recommends using actual laboratory test data of the dynamic and resilient modulus determined under simulated environmental and traffic loading conditions. To circumvent the need for conducting the mechanical test in lower design levels, predictive equations and correlations established with physical properties are used to estimate the mechanistic properties needed as input to the design software. This paper examines the simplifications incorporated in the model using results of dynamic and resilient modulus tests performed at the National Research Council Canada (NRC). Analysis of the data revealed that rating of materials is not consistent and mainly follows current binder and unbound material classifications, which does not necessarily conform to the actual response. Comparison between AC dynamic modulus measured in the laboratory and that predicted by the model lead to a relatively high average percent difference of 77%. Accordingly, an alternative approach is offered in this paper for adopting generic AC dynamic modulus values which may be developed from limited tests performed on local mixes and compiled in a database (material library). The paper discusses the accuracy expected from this alternative in comparison with the MEPD guide proposed approach involving the use of an empirical predictive equation.
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