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This study was motivated by the need for a mechanistic-empirical (ME) design method applicable to asphalt pavements after mill-and-overlay repairs that include reinforcing grids; the focus was solely on the mechanistic component. A new model, based on layered theory, was developed – coupling in one single framework the following features: elastic layers for representing subgrade and unbound layers, fragmented layers for representing existing aged and densely cracked asphalt concrete (AC), imperfect bonding conditions for representing any differential slippage between adjoining layers, thermo-viscoelastic layer properties for representing new AC, and moving loads for representing traffic conditions. Grid effects were modelled as a combination of three contributions: the presence of an additional thin high-modulus elastic layer within the pavement system, the influence of a grid on interlayer bonding between layer above and below it, and the influence of a grid on the properties of the surrounding AC. These contributions require new grid-related modelling inputs that are physically meaningful and generic – not limited to any specific product. A secondary objective of the work was to generate some initial intuition on the mechanistic effects of interlayer grids. Accordingly, the new model was demonstrated in a parametric investigation covering a synthetic milled-and-overlaid structure with and without reinforcement. Findings from this demonstration provided an initial validation for the new model, given the conformity to findings from experimental studies. Overall, the new model is deemed a candidate computational engine for a ME design applicable to new and rehabilitated asphalt pavement systems. Furthermore, it can serve as an analysis tool to guide manufacturers on improving their products or showcasing existing capabilities in a quantified manner. Lastly, the new model can support the design of experimental setups for assessing grid effects within asphalt pavement systems, and therefore ensure the collection of usable measurements for subsequent mechanistic interpretation. [ABSTRACT FROM AUTHOR]